Visual acuity measurement system

Abstract

Eye examination device making use of scaling anisotropies in optotype presentations to assist in the determination of visual acuity. In some embodiments, the range of corrective adjustments to scaling anisotropies available in a system is limited by the pixel structure of display optics used to present optotypes to test subjects. However, the scaling anisotropies themselves can be made use of to potentially expand the acuity testing resolution of a device. Effects of scaling anisotropies on the acuity threshold needed to correctly identify an optotype (among available options) are determined by measurements, modeling, and / or simulations. The effects are taken into account during testing, potentially allowing distinctions in test subject visual acuity thresholds finer than available from isotropic and / or integrally scaled pixel-based images alone. Optionally, anisotropies are deliberately introduced to some optotype presentations.

Description

[0001] VISUAL ACUITY MEASUREMENT SYSTEM

[0002] RELATED APPLICATIQN / S

[0003] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 606,982 filed on 6 December 2023, the contents of which are incorporated herein by reference in their entirety.

[0004] FIELD AND BACKGROUND OF THE INVENTION

[0005] The present invention in some embodiments thereof, relates to the field of vision testing, and more particularly, but not exclusively, to vision testing methods and targets for visual acuity examinations.

[0006] A common visual acuity exam usually includes a part where the subject looks at a visual acuity chart, usually placed at a distance of about 6 meters for the far visual acuity test or about 0.4 meters for the near visual acuity test.

[0007] The visual acuity chart may have symbols (optotypes) in different sizes and shapes. Among the common charts are the Snellen chart, the Landolt rings chart, the tumbling E chart and more. In these charts the symbols are in rows; each row contain at least one symbol. In a typical chart, each row contains symbols of the same size that represent a certain visual acuity; for example, an acuity expressed as a ratio such as 6 / 6.

[0008] The acuity ratio is typically designated for a subject based on the smallest symbol size line that they are able to recognize. The upper number refers to the distance the chart is from the patient (usually 6 meters or 20 feet), and the lower number refers to the distance in at which a healthy (reference) eye is able to read that line of the chart, in meters (e.g. 6 / 6, 6 / 9) or in feet (e.g. 20 / 20, 20 / 40). In some charts the subjects demonstrates recognition by reading out number s / letters, and / or identifying symbols. In other charts such as the Landolt rings and the tumbling E the subject recognizes the direction in which a gap or stroke (usually scaled to 1 / 5 of the symbol’s extent) of a symbol is pointing.

[0009] Acuity may alternatively be expressed as acuity according to the reciprocal of the visual angle subtended by the smallest gap / stroke feature which the subject is able to distinguish. At 6 / 6 acuity, for example, a symbol may subtend a visual angle of 5 arc minutes, and gaps / strokes a visual angle of 1 arc minute, resulting in a visual acuity of 1.0. SUMMARY OF THE INVENTION

[0010] According to an aspect of some embodiments of the present disclosure, there is provided a system useful to test refractive visual acuity of an eye of a test subject, the system including: an optical pathway which presents images including optotypes to a retina of the eye; and optical components in the optical pathway leading to the eye, including components which adjust presentation of the optotypes to compensate for refractive error in the eye; wherein adjusting the optical components produces anisotropic scaling of the presentation of the optotypes at the retina; and an acuity calculator, which receives responses of the test subject to the presentations of the optotypes, and calculates visual acuity of the subject using the responses, the calculated acuity also taking into account the anisotropic scaling of the presentation of the optotypes.

[0011] According to some embodiments of the present disclosure, the optical components which compensate for refractive error in the eye include at least one optical cylinder element which modifies the optical cylinder power of the optical pathway.

[0012] According to some embodiments of the present disclosure, the at least one optical cylinder element includes a plurality of cylinder lenses.

[0013] According to some embodiments of the present disclosure, the plurality of cylinder lenses includes at least two lenses, having refractive powers of opposite sign.

[0014] According to some embodiments of the present disclosure, the plurality of cylinder lenses includes at least three lenses, arranged along an optical axis of the optical pathway, and including, in order: a first lens with refractive power with a first value, a second lens with refractive power having a value arithmetically signed oppositely to the first value, and a third lens with a refractive power arithmetically signed the same as the first value.

[0015] According to some embodiments of the present disclosure, the images comprise pixels projected onto the retina.

[0016] According to some embodiments of the present disclosure, the optical pathway scales each of the pixels to a respective angular display resolution within a range between 0.1 arc minutes and 2 arc minutes.

[0017] According to some embodiments of the present disclosure, the angular display resolution of individuals of the pixels is anisotropically scaled by the adjusting of the optical components.

[0018] According to some embodiments of the present disclosure, angular display resolution of at least some of the pixels is different in different directions by at least 5%. According to some embodiments of the present disclosure, relative angular display resolution of at least some of the pixels varies for different adjustments of the optical components by more than 5%.

[0019] According to some embodiments of the present disclosure, an optotype presentation includes a feature three pixels in width or less, and having an angular display resolution of 1 arc minute or less.

[0020] According to some embodiments of the present disclosure, the feature extends along at least four pixels of the image at about a 45° angle relative to a grid arrangement of the pixels.

[0021] According to some embodiments of the present disclosure, the feature extends along at least four pixels of the image at about a 90° angle relative to a grid arrangement of the pixels.

[0022] According to some embodiments of the present disclosure, the acuity calculator determines effect of anisotropic scaling on the calculated visual acuity using predetermined values.

[0023] According to some embodiments of the present disclosure, the predetermined values are predetermined using one or more of the group consisting of: simulated images of optotype presentations, results of acuity tests used as calibration data, and calculations using parameters of the optical pathway.

[0024] According to some embodiments of the present disclosure, the system includes a sensor that records the images including optotypes as they are generated, and the acuity calculator uses measurements of the images to determine the anisotropic scaling of the presentation of the optotypes.

[0025] According to some embodiments of the present disclosure, the system monitors acuity thresholds tested by optotypes presented during testing of the eye; determines adjustments of the optical components which produce anisotropic scaling of a rescaled optotype presentation that allows the system to test an acuity threshold intermediate between the two of the acuity thresholds; and the system make the adjustments and presents the rescaled optotype presentation to the test subject to elicit acuity information about the eye.

[0026] According to some embodiments of the present disclosure, the system selects at least one of the group consisting of: a position of the optotype and an orientation of the optotype based on scaling anisotropy properties of the system.

[0027] According to some embodiments of the present disclosure, the system introduces optical distortion along a first image axis of an optotype presentation in order to adjust a magnification of a second image axis of the optotype presentation. According to an aspect of some embodiments of the present disclosure, there is provided a system useful to test refractive visual acuity of an eye of a test subject, the system including: an optical pathway which presents images including optotypes to a retina of the eye; and wherein the optical pathway produces anisotropic scaling of the presentation of the optotypes at the retina; and an acuity calculator, which receives responses of the test subject to the presentations of the optotypes, and calculates visual acuity of the subject using the responses, the calculated acuity also taking into account the anisotropic scaling of the presentation of the optotypes.

[0028] According to some embodiments of the present disclosure, the system selects the anisotropic scaling by choosing at least one of the group consisting of: a position in the optical field at which the optotype is presented; an orientation of the optotype presentation in the optical field.

[0029] According to an aspect of some embodiments of the present disclosure, there is provided a method for testing refractive visual acuity of an eye of a test subject, the method including: projecting illumination along an optical pathway to project an image including at least one optotype on a retina of an eye; and adjusting optical components in the optical pathway leading to the eye to compensate for refractive error in the eye; wherein adjusting the optical components produces anisotropic scaling of the presentation of the optotypes at the retina; receiving responses of the test subject to the presentations of the optotypes; and and calculating, using a processor, visual acuity of the subject using the responses, the calculating taking into account the anisotropic scaling of the presentation of the optotypes.

[0030] According to some embodiments of the present disclosure, the method includes adjusting at least one optical cylinder element which is among the optical components which compensate for refractive error in the eye, and adjusting the optical cylinder element modifies the optical cylinder power of the optical pathway.

[0031] According to some embodiments of the present disclosure, the images comprise pixels projected onto the retina.

[0032] According to some embodiments of the present disclosure, the adjusting optical components anisotropically scales angular display resolutions of individuals of the pixels.

[0033] According to some embodiments of the present disclosure, relative angular display resolution of the individuals of the pixels varies for different adjustments of the optical components by more than 105%.

[0034] According to some embodiments of the present disclosure, the calculating determines effect of anisotropic scaling on the calculated visual acuity using predetermined values. According to some embodiments of the present disclosure, the method includes measuring the images including optotypes as they are generated, and using measurements of the images to determine the anisotropic scaling of the presentation of the optotypes.

[0035] According to some embodiments of the present disclosure, the method includes: monitoring thresholds tested by optotypes presented during testing of the eye; determining adjustments of the optical components which produce anisotropic scaling of a rescaled optotype presentation for testing an acuity threshold intermediate between the two of the acuity thresholds; making the adjustments of the optical components; and presenting the rescaled optotype presentation to the test subject to elicit acuity information about the eye.

[0036] According to some embodiments of the present disclosure, the method includes introducing optical distortion along a first image axis of an optotype presentation in order to adjust a magnification of a second image axis of the optotype presentation.

[0037] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, controls. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

[0038] As will be appreciated by one skilled in the art, aspects of the present disclosure may be embodied as a system, method, or computer program product. Accordingly, aspects of the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system” (e.g.. a method may be implemented using “computer circuitry”). Furthermore, some embodiments of the present disclosure may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. Implementation of the method and / or system of some embodiments of the present disclosure can involve performing and / or completing selected tasks manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of some embodiments of the method and / or system of the present disclosure, several selected tasks could be implemented by hardware, by software or by firmware and / or by a combination thereof, e.g., using an operating system. For example, hardware for performing selected tasks according to some embodiments of the present disclosure could be implemented as a chip or a circuit. As software, selected tasks according to some embodiments of the present disclosure could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In some embodiments of the present disclosure, one or more tasks performed in method and / or by system are performed by a data processor (also referred to herein as a “digital processor”, in reference to data processors which operate using groups of digital bits), such as a computing platform for executing a plurality of instructions. Instruction executing elements of the processor may comprise, for example, one or more microprocessor chips, ASICs, and / or FPGAs. Optionally, the data processor includes a volatile memory for storing instructions and / or data and / or a non-volatile storage, for example, a magnetic hard-disk and / or removable media, for storing instructions and / or data. Optionally, a network connection is provided as well. A display and / or a user input device such as a keyboard or mouse are optionally provided as well. Any of these implementations are referred to herein more generally as instances of computer circuitry.

[0039] Any combination of one or more computer readable medium(s) may be utilized for some embodiments of the present disclosure. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device. A computer readable storage medium may also contain or store information for use by such a program, for example, data structured in the way it is recorded by the computer readable storage medium so that a computer program can access it as, for example, one or more tables, lists, arrays, data trees, and / or another data structure. Herein a computer readable storage medium which records data in a form retrievable as groups of digital bits is also referred to as a digital memory. It should be understood that a computer readable storage medium, in some embodiments, is optionally also used as a computer writable storage medium, in the case of a computer readable storage medium which is not read-only in nature, and / or in a read-only state.

[0040] Herein, a data processor is said to be “configured” to perform data processing actions insofar as it is coupled to a computer readable medium to receive instructions and / or data therefrom, process them, and / or store processing results in the same or another computer readable medium. The processing performed (optionally on the data) is specified by the instructions, with the effect that the processor operates according to the instructions. The act of processing may be referred to additionally or alternatively by one or more other terms; for example: comparing, estimating, determining, calculating, identifying, associating, storing, analyzing, selecting, and / or transforming. For example, in some embodiments, a digital processor receives instructions and data from a digital memory, processes the data according to the instructions, and / or stores processing results in the digital memory. In some embodiments, “providing” processing results comprises one or more of transmitting, storing and / or presenting processing results. Presenting optionally comprises showing on a display, indicating by sound, printing on a printout, or otherwise giving results in a form accessible to human sensory capabilities.

[0041] A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electromagnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

[0042] Program code embodied on a computer readable medium and / or data used thereby may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

[0043] Computer program code for carrying out operations for some embodiments of the present disclosure may be written in any combination of one or more programming languages, including an object-oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. Additionally or alternatively, sequences of logical operations (optionally logical operations corresponding to computer instructions) may be embedded in the design of an ASIC and / or in the configuration of an FPGA device. The program code may execute entirely on the user’s computer, partly on the user’s computer (e.g., as a stand-alone software package), partly on the user’s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user’s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0044] Some embodiments of the present disclosure may be described below with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the present disclosure. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0045] These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function / act specified in the flowchart and / or block diagram block or blocks.

[0046] The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0047] Some of the methods described herein are generally designed only for use by a computer; and may not be feasible or practical for performing purely manually, by a human expert. A human expert who wanted to manually perform similar tasks, such inspecting objects, might be expected to use completely different methods, e.g., making use of expert knowledge and / or the pattern recognition capabilities of the human brain, which would be vastly more efficient than manually going through the steps of the methods described herein. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0048] Some embodiments of the present disclosure are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example, and for purposes of illustrative discussion of embodiments of the present disclosure. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the present disclosure may be practiced.

[0049] In the drawings:

[0050] FIG. 1 A schematically illustrates a cylindrical refractive error correction unit, according to some embodiments of the present disclosure.

[0051] FIG. IB schematically illustrates a cylindrical refractive error correction unit, according to some embodiments of the present disclosure.

[0052] FIGs. 2A-2B schematically illustrate pupil effects of the introduction of cylindrical correction in one- and two-lens cylindrical correction units, according to some embodiments of the present disclosure;

[0053] FIGs. 3A-3B schematically illustrates an optical system comprising subjective and objective testing optical subsystems, according to some embodiments of the present disclosure;

[0054] FIG. 4 schematically illustrates an optical system providing a separate objective testing illumination source, according to some embodiments of the present disclosure;

[0055] FIG. 5A schematically illustrates a cylindrical refractive error correction unit in combination with a spherical refractive error correction unit, according to some embodiments of the present disclosure;

[0056] FIG. 5B schematically illustrates a cylindrical refractive error correction unit in combination with a screen illumination source, according to some embodiments of the present disclosure;

[0057] FIG. 6 schematically illustrates a block diagram of an optical system combining objective and subjective eye refraction testing subsystems, according to some embodiments of the present disclosure;

[0058] FIG. 7 schematically illustrates a block diagram of a variant of optical system combining objective and subjective eye refraction testing subsystems, and having a dual-use scanning unit, according to some embodiments of the present disclosure; FIG. 8 schematically illustrates a block diagram illustrating optical modules of a variant of optical system combining objective and subjective eye refraction testing subsystems, and having a dual-use scanning unit, according to some embodiments of the present disclosure;

[0059] FIG. 9 schematically illustrates a block diagram illustrating optical modules of a variant of optical system combining objective and subjective eye refraction testing subsystems, having a dual-use scanning unit, according to some embodiments of the present disclosure;

[0060] FIG. 10 is a schematic optical diagram of the objective testing optical subsystem of optical system of Figure 9, according to some embodiments of the present disclosure;

[0061] FIG. 11 is a schematic optical diagram of the Scheiner principle, performed, for example, using the optical arrangements of Figure 10, according to some embodiments of the present disclosure;

[0062] FIG. 12 is a schematic optical diagram of a subjective testing optical subsystem, according to some embodiments of the present disclosure;

[0063] FIG. 13 is a schematic optical diagram of combined objective and subjective testing optical subsystems of an optical system, according to some embodiments of the present disclosure;

[0064] FIG. 14 is a schematic optical diagram of combined objective and subjective testing optical subsystems of an optical system using two scanning units, according to some embodiments of the present disclosure;

[0065] FIG. 15 is a schematic optical diagram of combined objective and subjective testing optical subsystems of an optical system, with the objective testing optical subsystem using ray tracing aberrometry, according to some embodiments of the present disclosure;

[0066] FIG. 16 is a schematic flowchart of a method for measuring the refractive error of subject’s eyes and providing a prescription for eyeglasses or contact lenses, according to some embodiments of the present disclosure;

[0067] FIG. 17 is a schematic flowchart of a method to align a subject’s eye to an optical system, according to some embodiments of the present disclosure;

[0068] FIG. 18 schematically illustrates a compact visual acuity and / or refractive error testing system, according to some embodiments of the present disclosure;

[0069] FIGs. 19A-19B schematically represent table-top use of compact visual acuity testing kit to perform visual acuity testing on a subject, according to some embodiments of the present disclosure;

[0070] FIG. 19C schematically illustrates a refractive error examination system installed in a kiosk stand, according to some embodiments of the present disclosure; FIGs. 20A-20C schematically illustrate head-worn implementations of a vision testing system, according to some embodiments of the present disclosure;

[0071] FIGs. 21A-21E illustrate examples of optotypes based on a 5x5 grid, according to some embodiments of the present disclosure;

[0072] FIGs. 22A-22B illustrate examples of optotypes at different rotations, according to some embodiments of the present disclosure;

[0073] FIG. 23 illustrates a square-pixel rendering of optotype on 10x10 grid with two-pixel wide strokes (and gaps between them), according to some embodiments of the present disclosure;

[0074] FIG. 24 illustrates a square-pixel rendering of optotype on a 15x15 grid with approximately two-pixel wide strokes (and gaps between them), according to some embodiments of the present disclosure;

[0075] FIGs. 25A-25B show optotypes in a same corresponding orientation, allowing comparison of their dimensions, according to some embodiments of the present disclosure;

[0076] FIGs. 26A-26E illustrate different anisotropic optical scaling transformations of an optotype, according to some embodiments of the present disclosure;

[0077] FIGs. 27A-27E illustrate different anisotropic optical scaling transformations of an optotype, according to some embodiments of the present disclosure; and

[0078] FIG. 28 is a schematic flowchart representing a method of subjective visual acuity testing using anisotropically magnified optotype presentations, according to some embodiments of the present disclosure; and

[0079] FIG. 29 schematically illustrates positioning of optotype presentations at different locations in a visual field, according to some embodiments of the present disclosure.

[0080] DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

[0081] The present invention in some embodiments thereof, relates to the field of vision testing, and more particularly, but not exclusively, to vision testing methods and targets for visual acuity examinations.

[0082] Overview

[0083] Variable Optics-Generated Scaling of Optotypes in Visual Acuity Testing

[0084] An aspect of some embodiments of the present disclosure relates to the use of scaling of visual stimuli in visual testing, and, in some embodiments, anisotropic scaling in particular. In some embodiments, the visual testing performed is “subjective” testing, in which the test results comprise some form of test subject report about the stimulus that they see. More particularly, the subjective testing tests visual acuity related to the refractive properties of the test subject’s eye(s). Test results are optionally used, e.g., to determine a prescription for visual correction, e.g., eyeglasses, sun glasses and / or contact lenses. Optionally, test results are used in assessing a test subject’s visual acuity for another purpose, e.g., to assess their suitability for a task and / or for receiving a procedure. In some embodiments, test results are sued for defining optical properties for a wearable device, e.g., optionally including, but not limited to, artificial reality (AR) devices, mixed-reality (MR) devices, virtual reality (VR) devices, binoculars, or another active or passive device which presents and / or directs images to the eyes.

[0085] In some embodiments, the visual testing comprises use of an at least partially automated stimulus presentation device. In overview, the device includes an optical pathway which presents images containing visual stimuli (optotypes) to the eye(s) of test subjects. Elements of the optical pathway have variable settings, the variable settings being used to adjust for refractive error in the eye(s) of the test subject. This in turn modifies at least the degree of focus of optotype images reaching the retina(s) of the eye(s). In some embodiments, the optical components of the optical pathway (e.g., components which generate and / or modify the light beam in its structure, composition, and / or direction, optionally including mirrors, filters, lenses, illuminating devices, and / or prisms) also variably determine the scaling of the optotypes, according to their settings (e.g., positioning and / or shape). This may include settings selected to compensate for refractive error of the eye(s), and / or settings which are selected to modify the scaling as such. In some embodiments, the scaling includes at least scaling anisotropy of the optotype presentations. The determined scaling anisotropy is then used in calculating visual acuity testing results (by an acuity calculator). Additionally or alternatively, changes in overall scaling due to optical power changes may be determined and used in the calculating. The acuity calculator, in some embodiments, comprises a computer processor and memory, wherein the memory includes instructions which instruct the processor to perform the calculating taking into account effects of scaling anisotropy on the optotype presentations. The calculating also take into account responses received from the test subject

[0086] For example, in some embodiments, the process of acuity testing includes the introduction of a potentially varying amount of cylinder correction (optical power greater along one axis than along an orthogonal axis) to the optics relaying optotype presentations to the retina of the test subject (herein the term “subject” may be understood to refer to the “test subject” wherever the substitution is appropriate to the meaning of “a person undergoing visual acuity testing”). In some embodiments, this cylinder correction is allowed to also introduce anisotropic magnification (different scaling of, e.g., width and height, from the viewpoint of the subject) to the presented optotype. During testing, the system tracks the directions and amounts of such anisotropies, along with the properties of co-presented optotypes (e.g., size, shape, and / or orientation). The system may be provided with predefined data which describe these anisotropies. For example, in some embodiments of the present invention, the gap and / or stroke width for each position, rotation, size and / or color of an optotype is measured empirically, and / or found from simulations and / or other calculations. In some embodiments, the system is provided with a capability for detecting these sizes itself, e.g., based on sensor imaging of a beam-split portion of the light sent to the eye of the subject.

[0087] Using this information, together with a current optical setting of the system, an optotype or optotypes may be selected for projection using a size (in pixels, the pixels being display elements which provide illumination used to generate the image which presents the optotype), position, color, and / or orientation such that the subject’s recognition of the optotype’s shape, orientation, or other recognizable feature is indicative of visual acuity information needed to complete the test. In some embodiments, the optical settings may themselves be adjusted, jointly with selection of the optotype presentation parameters, in order to ensure that visual acuity information needed to complete the test is obtained.

[0088] To produce visual acuity test results, the system then accounts for what the subject actually saw. For example, the system may determine that a distinguishing feature of an optotype appeared as relatively larger or smaller to the subject, depending on how it was oriented relative to magnification anisotropies of the device as actually configured. Optionally, mistakes by a subject in identifying optotypes are related to the particular magnifications of optotype features; e.g., two different optotypes presented may be more or less easily confused with one another according to which specific features are oriented along a less-magnifying or more-magnifying optical axis.

[0089] In some embodiments, apparent magnification of presented optotypes is allowed (additionally or alternatively) to change as a function of spherical optical power, and the system tracks and corrects this, optionally together with the anisotropic scaling of the presented optotypes.

[0090] Presentations of Optotypes

[0091] Optotype presentations are projected to the retina of a subject for evaluating properties of a subject’s vision, such as spherical power cylindrical power and / or cylindrical axis, depth perception, double vision and other vision related properties. Optotype gap width or / and stroke (traditionally 1 / 5 of the optotypes overall dimensions) is optionally rotated to different orientations.

[0092] Optionally, optotype(s) are presented to appear in (or as if in) 2-D or 3-D space. Presentation may be monocular and / or binocular; presentation may be dynamic (e.g., presentations may appear to move in the field of view) or fixed. An optotype may be presented (e.g., projected) in different positions or in different orientations, optionally in arbitrary locations. Optotypes are optionally presented in simultaneous patterns arranged disordered, or order in any suitable alignment, such as by row, column, diagonal and / or any combination thereof.

[0093] For (binocular) 3-D presentations, the optotypes may be positioned in different depths as well as any of the possibilities suitable for 2-D positioning of optotypes. Optotypes may themselves be 3-D in appearance, e.g., as seemingly flat elements presented at particular depths, angled in depth, and / or or as volumetric elements. Some of these 3-D presentation methods may be used to mask or “naturalize” distortions due to optics, e.g., an element may be presented as angled in depth (e.g., using binocular cues) along an axis which also corresponds to an axis of lessened magnification, allowing foreshortening to “account for” the relative decrease in magnification.

[0094] Resolution and Optical Distortion Interactions with Visual Acuity Testing

[0095] Without limitation to particular means of implementation, in many optical systems which present a virtual image to a subject’s retina, there are limits to resolution characterized by how a given pixel count resolution (number of pixels overall available to a device) is scaled to angular resolution for presentation to the eye. Accordingly, the visual angle subtended by a pixel may be considered as corresponding to the angular display resolution of the system. For example, the system may provide pixels each subtending a visual angle of from about 0.1 arc minutes to about 1 arc minute (fixed or variable, and not necessarily the same value in all directions). The ideal value set by pixel angular size is referred to herein as the angular display resolution. This value does not attempt to take into account other optical factors which may degrade the apparent separation of pixels; e.g., degradation that causes two lit pixels separated by a dark pixel to be perceived as separated by less than one pixel.

[0096] While angular display resolution values outside of the 0.1 arc minute to 1 arc minute range are not excluded (e.g., the angular display resolution is an range between 0.1 arc minutes and 2 arc minutes, in some embodiments), it is noted that for eye testing, visual acuity is typically established up to a “normal eye” limit of features subtending and / or separated by about 1 arc minute. A higher angular resolution of the system’s display may unduly reduce the available field of view (e.g., it might reduce a maximum size at which optotypes can be presented); a lower angular resolution may be insufficient for acuity testing.

[0097] Accepting an angular resolution limit close to 1 arc minute may, however, result in only a small number of pixels being available to display optotypes at smaller angular sizes. For example, to distinguish optical acuities at 6 / 9, 6 / 7.5, and 6 / 6 (the 6 in the numerator corresponding to 6 meters actual or virtual viewing distance) or 20 / 30, 20 / 25, and 20 / 20 (the 20 in the numerator corresponding to 20 feet, roughly equal to 6 meters), testing should distinguish visual acuities resolving about 1.5, 1.25 or 1 arc minutes.

[0098] For an optotype based on a (typical) 5x5 grid, a system with 0.5 arcminute angular resolution can test 6 / 6 resolution with a presentation sized to 10 pixels, having gap and stroke each only 2 pixels wide (1 arc minute). The same optotype testing 6 / 9 acuity has a size of 15 pixels, with 3 pixels for the gap / stroke width (1.5 arc minute). However, for testing the intermediate acuity of 6 / 7.5, the system is constrained by its display to make an adjustment: for precise display, the gap / stroke width should equivalent to be 2.5 pixels, but half a pixel generally cannot be presented as such (although image modifications such as anti-aliasing and sub-pixel addressing may simulate “half presentation”, this also modifies the sharpness of stimulus presentation itself). This constraint exists also for targets smaller than 6 / 6 such as 6 / 5, 6 / 4 and for 6 / 3.

[0099] Moreover, in some embodiments, the design of optotype and / or other stimulus presentation may call for apparent variations in depth, e.g., making use of eye vergence which should potentially be associated with appropriate scaling differences as well.

[0100] As noted, a typical solution for displaying small features uses pixel anti-aliasing; however, this can, in effect, blur the stimulus itself, which is potentially difficult to separate from blurring by the optics of the subject’s own eye. However, anti-aliasing is optionally used where its effects can be determined (e.g., calibrated for).

[0101] As an alternative, optotype size may be varied by deliberately varying the angular display resolution (“pixel size”). However, in the case of a subjective visual acuity testing system, the optics which relay the optotype presentation to the subject eye are likely already varying optical power in various ways to test eye acuity. This does not necessarily preclude changing stimulus size to a deliberately selected magnification by adding variable magnification optics, but system complexity may be undesirably increased by adding further requirements to the system, without careful consideration. In some embodiments optical adjustments already present may provide suitable control for adjusting the effective angular display resolution of an acuity testing system. Dynamic Optical Distortions as Visual Acuity Testing Enhancements

[0102] According to some embodiments of the present disclosure, there are provided systems for visual acuity testing configured to present one or more optotypes in a manner which varies according to one or more inhomogeneities in the optics of the system which relay illumination generated by a display illumination device to the eye of the subject. These inhomogeneities are distinguished from stimulus definitions addressed to the display illumination device itself (e.g., images defined as pixels corresponding to illumination elements, times, and or addresses of the illumination-generating display hardware itself). The inhomogeneities may change over time, e.g., according to current settings of the testing optics. The changes may, in particular, correspond to optical adjustments which modify optical power as part of visual acuity testing itself, e.g., to counteract refractive error in the eye of the subject. The inhomogeneities include, in some embodiments, anisotropic scaling of optotype presentations, for example, anisotropic scaling associated with cylinder lens power corrections placed in the optical path.

[0103] Additionally or alternatively, different spatial positions in the field of view may be provided with different angular display resolutions. For example, the field of view may be provided with regions having relatively greater or smaller magnification factors (potentially different for different directions), and the position of display of an optotypes may be selected to gain use of a particular magnification factor.

[0104] The inventors of the present disclosure have realized that angular display resolution changes and / or anisotropies in scaling may occur intentionally and / or incidentally as effects of the optics of a subjective visual acuity testing system. They have furthermore realized that these effects may be viewed, not as necessarily parasitic or undesirable, but rather made use of to augment visual acuity testing capabilities of a testing device.

[0105] Even statically, the width and length of a pixel (its angular display resolution) are not necessarily both the same. This may be due to the display itself: e.g., lines of a scanning display may be pitched differently than horizontal step size associated with a change in luminosity distinguishing pixels, or a fixed-dimension display may simply be built with different horizontal and vertical pitches.

[0106] Furthermore, variation of optical system parameters which occur during testing itself (e.g., to interpose different levels of optical power into the testing system) may itself tend to introduce variable magnification levels, including anisotropic variation of magnification. It may require specific design attention, in particular, to maintain one or both of constant magnification and axis scaling symmetry (preventing anisotropy) in an optical system that has changeable / moveable optical elements that may modify optical properties as part of the testing methodology itself. Examples of such properties include, for example, but are not limited to: spherical power, astigmatism power, and astigmatism axis.

[0107] Furthermore, control of the above test-varying optical properties is coordinated, in some embodiments, with control of other optical properties that can (intentionally or unintentionally) modify the way an image is perceived by a user. These other optical properties include, for example, but are not limited to: apparent distance, size (e.g., size in pixels), color, exit pupil position, and / or exit pupil size.

[0108] According to some embodiments of the present invention the feedback from the subject on the different optotypes projected, may be used to evaluate the subject’s vision even when the optotype’ s / optotypes’ gap / stroke width doesn’t exactly corresponds to 6 / 3, 6 / 4, 6 / 5, 6 / 6, 6 / 7.5, 6 / 9 vision or other vision evaluations between 6 / 3 and 6 / 9 or 20 / 10 and 20 / 30 The evaluation may be used but not limited for a prescription for glasses / contacts or for defining optical properties for wearable devices such as but not limited to AR / MR / VR or other XR devices.

[0109] Anisotropic Scaling Terms and Definitions

[0110] Herein, “anisotropic scaling” refers to presentation of an optotype having features with the same ratio of smallest salient feature extent to overall (maximum) optotype extent in each of two orthogonal directions — but the overall extents themselves are different (at least in some presentations) for the two directions. For example, an E-shaped optotype may be based on a 5x5 grid of squares, but scaled so that the ratio of the horizontal and vertical extents of the grid is other than 1 — e.g. about 0.8, 0.85, 0.90, 0.95, 1.05, 1.1, 1.15, 1.2, 1.25, or another (e.g., larger) ratio. The ratio is referred to herein as the “scaling ratio”. The difference of horizontal vs. vertical scaling in percent may be, for example, greater than or equal to 5%, 10%, 15%, 20%, or 25%. The differences in scaling are not necessarily orthogonal to the horizontal and vertical axes, either; the same differences in scaling ratio may be seen between axis oblique to the horizontal and vertical axes. Moreover, the scaling ratio may be different under different operating conditions of the visual acuity testing system; for example, 1 or near to 1 at a baseline condition (e.g., a condition without cylinder correction introduced), up to one of the above-given differences, or potentially a larger difference.

[0111] Herein, scaling ratio is considered as a ratio of horizontal to vertical scaling, with “horizontal” and “vertical” selected as noted below. For the sake of explanations herein, “scaling anisotropy” itself is considered as always being a value of 1 or greater, and is either the scaling ratio itself, or its reciprocal; e.g., scaling ratios of 0.8 and 1.25 have the same scaling anisotropy of 1.25.

[0112] Herein, the “salient” features are those which are relied on by the subject in distinguishing the optotype, and / or at least those which the subjective testing design itself anticipates subjects will rely on. For example, the gap between two horizontal strokes of an E-shaped stimulus may be considered salient, optionally in conjunction with the strokes themselves. Irregularities at the boundaries of strokes, half-toning patterns, sub-pixel illumination gaps and other such artifacts are non-salient, e.g., not reported by and / or not meant to be reported by subjects undergoing testing. Features well below the resolution of normal eye acuity (e.g., less than 0.1 arc minutes) may be considered non-salient unless specified otherwise according to the design of the optical test and / or optotype itself. It is noted that in the phenomenon of “hyperacuity” (e.g., vernier acuity), contrast boundary offsets on the retina of much less than the nominal size of the retina’s photosensitive cells may be noticed by a subject, e.g., at feature sizes about a factor of ten smaller than features used in establishing optometric visual acuity.

[0113] During typical visual acuity testing, as well as in embodiments of the present disclosure, optotype presentations may vary at least in size (e.g., subtended visual angle). In the case of a tumbling E chart, optotype presentations also vary in orientation of the optotype; e.g., the limbs of an E (or other optotype) may point (be open on the side towards) up, down, left, or right. In some embodiments of the present disclosure, optotype presentation scaling ratio also varies, along with or separately from optotype presentation size and / or orientation.

[0114] Furthermore, variation in the relative orientation of the axes of anisotropy is optionally the same as or different from variation in the orientation of the presented optotype itself.

[0115] In some embodiments, for example, the scaling axes optionally are in a fixed relationship to the shape of the optotype (at whatever presentation orientation), e.g., the scaling anisotropy may be largest when measured with one axis extending along the (ordinary upright) vertical stroke of an E, compared to a second axis extending along the horizontal strokes of the E, even if the E itself is rotated. Additionally or alternatively, in some embodiments, the scaling axes may (at least sometimes) be oblique to the canonical axes of the optotype. In particular, the directions of the scaling axes may be connected to (e.g., controlled at least in part by and / or maintained in constant correspondence with) the layout of a pixel array and / or scanning pattern of an underlying display device used for the optotype presentation. Additionally or alternatively, the scaling axes may be connected to (e.g. , controlled at least in part by and / or maintained in constant correspondence with) the optics of the testing device which convey the optotype presentation to the eye of the subject being tested. In particular, the scaling axes may be controlled by modification of the optical power and / or orientation of cylinder aberration created within the optics of the testing device.

[0116] Some embodiments of the present disclosure making use of anisotropic scaling are characterized by the inclusion of an estimated scaling ratio and / or scaling anisotropy other than 1 in the calculations of visual acuity results. Optionally, and more particularly, such embodiments are optionally characterized by use of a plurality of values of estimated scaling ratio and / or scaling anisotropy to calculate a visual acuity result.

[0117] Optionally, use of anisotropic scaling in embodiments of the present disclosure comprises differential treatment of spatial axes in calculations of visual acuity, not necessarily with explicit use of a scaling ratio value as such. For example, calculations for different axes may be distinguished by the use of differently valued weighting and / or scaling factors.

[0118] Optionally any of said factors, and / or the estimated scaling ratio and / or scaling anisotropy value vary among a plurality of values dependent on device settings, e.g., values selected as appropriate for the optical and presentation settings of the device during each optotype presentation.

[0119] Visual Acuity Testing Systems

[0120] A broad aspect of some embodiments of the present disclosure relates to vision testing systems and / or methods configured for both objective and subjective measurement of eye refraction (an important factor in visual acuity); for example, to determine corrective lens prescriptions for eyeglasses and / or contact lenses. The measurements and / or determination of an associated corrective lens prescription comprise, in some embodiments, determination of refractive error (quantifying eye refraction) and / or visual acuity (a measure of the spatial resolution of the visual processing system overall, determined subjectively, and affected by eye refraction).

[0121] In some embodiments, an objective testing optical subsystem comprises at least one beam source, and optics that direct light from the at least one beam source to the subject’s eye, along one or more optical pathways. In some embodiments, the optical pathway includes a scanning mirror (e.g., a microelectromechanical system [MEMS] scanning mirror), configured to direct incident light from the at least one beam source to different locations (e.g., via adjustment of the angle of the mirror). This is used, for example, to produce light patterns appropriate for testing, which project onto the subject’s eye. In some embodiments, the mirror is operated at a scanning speed producing a frame rate greater than 30 Hz, preferably larger than 50 Hz. The resolution is preferably suitable to produce, e.g. , 800 x 600, 1280 x 720 or a higher pixel resolution image. After added optics, this may be used to produce an image with at least about 1 arcminute, 0.5 arcminutes, or 0.3 arcminutes of resolution (e.g. , a resolution sufficient to allow detection of human eye optical acuity loss within ordinarily accepted limits of optical acuity testing). Optionally, the angular size of the image subtends, for example, about ±5° horizontally (e.g., at least ±3°), and about ±3° vertically (e.g., at least ±2°).

[0122] In some embodiments, light from a first beam source reflected from a surface of the eye is directed to a sensor and analyzed. The sensed reflected light carries refractive information, used in the analysis to estimate the objective refraction of the subject’s eye. Light emitted from the first beam source may be in the near infrared (IR), e.g., a wavelength greater than 640 nm. Optionally or additionally, light of another wavelength is used.

[0123] During an objective visual acuity exam, the subject focuses on a target. The target optically comprises a blurred region, e.g., a blurred background region, and optically an element moving in apparent depth, e.g., moving away from the viewing subject. In some embodiments, the scanning mirror is used also to create the target that the subject focuses on, e.g., a target formed from light emitted by a second beam source. In some embodiments, the second beam source, scanning mirror and optical pathway used for creating the target in the objective visual acuity exam are also used in the subjective visual acuity exam for presenting visual acuity charts and / or other images.

[0124] In some embodiments, a subjective testing optical subsystem is configured for determining the refraction of a subject’s eye subjectively, based on subject reporting of the appearance of test images produced by a projection unit. The images, in some embodiments, are projected onto the retina of the subject by scanning one or more laser beams from a beam source (e.g., the second beam source) in two dimensions. Scanning is produced, e.g., by adjustment of a scanning mirror angle. Optionally, the same mirror is used in both subjective and objective testing.

[0125] In some embodiments, the subjective testing optical subsystem includes a defocusing assembly unit, acting as the phoroptor of the device to apply adjustable corrective refractive power comprising at least a spherical correction applied to the image the subject sees. The defocusing unit is adjustable to produce step and / or continuous changes in the divergence or convergence of the laser beam. Subject feedback is used to determine the refractive power which best corrects the subject’s vision.

[0126] The subjective testing optical subsystem optionally includes a cylindrical and axis optical correction assembly. This introduces an adjustable distortion to the shape of the scanned laser beam. During acuity testing, adjustment is selected to counteract the cylindrical and axis error of the subject’s eyes, e.g., based on feedback from the subject reporting how clearly a target is seen, and / or what target is seen and / or distinguishable. In some embodiments, the subsystem includes an optical relay, configured to provide magnification as appropriate, and bring the exit pupil of the optical subsystem to the subject’s eye. When the second beam source is used to present the focus target presented together with the objective visual acuity exam, the defocusing assembly unit and cylindrical and axis optical correction assembly optical subsystem may be present in or removed from the optical path. If present, they are optionally adjusted to neutral settings (e.g., neutral positions), or to positions which are known and / or estimated to fully or partially correct refractive error of the eyes of the subject.

[0127] In some embodiments, a starting point which sets shaping of the scanned beam in the subjective visual acuity exam is based on available data indicative of the subject’s refractive error. The data comprise, for example, the subject’s previous prescription, measurements of currently used prescription lenses, and / or any other available information related to a subject’s vision or eye medical history. Additionally or alternatively, the initial configuration is based on data obtained from an objective visual acuity exam, e.g., an exam performed using the objective testing optical subsystem. The objective testing optical subsystem optionally makes use of any appropriate objective lens characterizing effect, principle, sensor, and / or method, for example, Shack- Hartmann wavefront sensing, knife edge effect, image size principle, ray tracing aberrometry, and / or Scheiner principle.

[0128] The initial configuration is optionally set exactly according to the best available data or offset from it, e.g., with an added or subtracted factor. For example, about 2-4 diopters (e.g., 2, 3, or 4 diopters) of positive or negative offset is applied to reduce accommodation. Based on feedback from the subject, the spherical, cylindrical and axis are adjusted, until their combined correction produces the best-seen image on the subject’s retina. From parameters which characterize the changes to the scanned beam (e.g., divergence / convergence, astigmatism and cylindrical axis) which produce the optimized image on the subject’s retina, the subjective spherical, cylindrical and axis error are determined, providing information for an eyeglasses or contact lenses prescription, optionally in conjunction with additional information such as corneal curvature.

[0129] Optionally, one or both of the objective and subjective testing optical subsystems is duplicated (e.g., copied in at least their major optical features, optionally with packaging adjustments such as mirror imaging of component layout), allowing both eyes to be tested simultaneously or alternately without adjusting the position of the system. Preferably, images produced by the duplicate systems on are binocularly registered to produce a perceptually unified image for the subject (assuming the subject is capable of depth perception within the range of physical settings available to the device). This optionally produces a sense of depth in the image. Optionally, the binocularly registered image includes differences between images, comprising, for example, depth cues and / or feature differences used in testing.

[0130] Optionally, one or both of the objective and subjective testing optical subsystems can be shunted alternately to either eye (e.g., using a mirror), and / or is visible simultaneously to each eye (e.g., using a prism and / or beam splitter. For example, in some embodiments, objective acuity testing occurs at least partially concurrently with subjective acuity testing. For example, objective visual acuity testing may make an incidental use of a subjective visual acuity test target as the attention-drawing stimulus which helps to set the subject’s lens accommodation. It is emphasized in particular with regard to this concurrency that objective visual testing optionally uses IR (invisible) wavelengths for the testing itself, and optionally shares the same display for target presentation as is used during subjective visual acuity testing.

[0131] Optionally, intermediate results of one testing modality are used to adjust testing of the other modality, and optionally iteratively. For example, objective visual testing may be used to set an initial range of subjective visual testing corrective power to test, while results of the subjective testing may then be used to adjust the presentation of visual stimuli which help set the accommodation of the subject for further objective visual acuity testing, and / or to adjust the range of test parameters within which further objective testing is concentrated. Insofar as the same device performs both functions, such mutual reinforcement of results is potentially enabled without a requirement to reposition the subject / device, or even to perceptibly interrupt one test type in order to perform the other.

[0132] An aspect of some embodiments of the present disclosure relates to providing capabilities in a combined objective and subjective visual acuity testing device with internal display, which said capabilities promote the guidance and / or control of subject attention, eye vergence (inter-eye difference in angle of viewing), and / or lens accommodation. In some embodiments, the capabilities promote the combination of the visual acuity testing device with other devices making use of external screens, e.g., devices for teleconferencing and / or auxiliary visual testing. In some embodiments, capabilities are provided which allow enhancements to visual acuity testing relating to speed, comfort, accuracy, and / or automaticity of testing.

[0133] In some embodiments, images are delivered simultaneously to both eyes. This potentially promotes using the testing device to influence the state of the subject’s eyes by manipulation of factors including, for example: • Inter-pupil distance (IPD), which can be changed mechanically, e.g. , by moving the exit pupils of device optics further or closer to each other in a horizontal direction. Optionally, a system is configured with degrees of freedom to adapt mechanically to other aspects of a subject’s anatomy as well; e.g., to account for relative vertical displacement and / or relative depth displacement of the subject’s eyes relative to the facing plane.

[0134] • Eye vergence, which can be changed, e.g., by altering the angle of mechanical and / or optical elements of the system, e.g., mirrors and / or prisms (though the latter is liable to introduce chromatic aberration). Optionally, the whole optical subsystem for an eye is moved, which provides the potential advantage of maintaining a constant optic axis once the eye itself adjusts position to th new angle. For example, an eye vergence of about 1° is typical for viewing a target at a range of about 3-6 meters, while an eye vergence of about 3° is typical for viewing a target at a range of about 0.4 meters.

[0135] It is noted that particularly when the maximum visual field size of presented images is relatively small (e.g., ±5°), the use of mechanical movements of the system to adjust eye vergence may help preserve substantially the whole area available for visual presentation. In some embodiments, eye vergence is adjusted (additionally or alternatively) by displacing the generated images left / right within the available visual field size of the retinal scanning display ( / '.<?., displacing the images digitally). Mechanical adjust went of eye vergence provides the potential advantage (compared to digital image displacement) of maintaining a constant angle to the eye, as the eye angle moves to follow the new angular position. For example, it potentially maintains an angle at which an objective visual acuity test pattern is projected onto the retina.

[0136] In some embodiments, a combined-testing device is configured to internally generate and present test and / or target images to one or both eyes of a subject. In some embodiments, the generated images are optionally delivered to the eye(s) through a beam which is also combined with light collected from in front of the subject, so that the subject sees the generated images combined with an optically formed image of their surroundings (e.g., an augmented reality or AR view). This potentially assists in setting and / or controlling the lens accommodation of the subject. For example, arbitrary objects (e.g., an attention-drawing objects such as a toy; actually present in the environment and / or shown as 3-D images) may be shown to a child subject to draw their attention through the passthrough image collected from the surroundings. Optionally, a person familiar to such a subject can draw the subject’s attention from in front of the subject via the passthrough image. The objects of the surroundings in any case potentially assist by providing a familiar visual context to the subject’s visual system. The passthrough image also potentially promotes interaction between the subject and the eye examiner (optometrist) and / or technician (assistant), since the subject’s view is then not necessarily isolated to what is generated within the testing device.

[0137] In some embodiments, brightness of the generated images is adjustable (e.g., by adjusting laser power, polarizers, filters, and / or LC filters) to conduct the vision acuity exam under targeted conditions (e.g., as standardized, common, or optimal according to the preferences of the test administrator(s)). Optionally, the brightness of the surroundings is adjusted, e.g., using an adjustable polarizer, transparent LCD, or other device. This has potential advantages for allowing the subject to comfortably view the test targets in a wide range of ambient illumination conditions, so that use can be made of the subject’s natural optical accommodation responses to the positions of objects in actual surroundings.

[0138] In some embodiments, passthrough of the surroundings promotes combination of the image presentation capabilities built into the testing device with other displays such as teleconferencing displays and / or special testing displays which may be separately available in an examination setting. For example, the subject can interact with (e.g., take instructions from / ask questions to) a test examiner visible on a teleconferencing screen without necessarily interrupting visual acuity testing and / or positioning with respect to a visual acuity testing device. The external screen may be used to present images which draw the attention of the subject, e.g., in place of a toy or other attention- attracting object.

[0139] In some embodiments, a visual acuity testing device includes supporting functions such as eye tracking, which optionally includes, more specifically, one or more of eye position (e.g., eye vergence) tracking, eye lens accommodation tracking, and / or pupil size tracking. Together with the passthrough capability, this allows optional use of the device together with an external screen which, e.g., presents stimuli for auxiliary assessment of vision, visual attention, or another purpose. With or without the use and / or presence of passthrough capability, eye tracking functions are optionally used internally to assess the validity of test results (e.g., objective visual acuity testing) during different trials. Optionally, loss of correct eye positioning is used to trigger corrective and / or alerting measures, e.g., repositioning of device optical pupils, alteration of presented visual stimuli, discarding of bad data, and / or presentation of a warning to the device operator.

[0140] In some embodiments, presentation of images to both eyes or just one eye is varied as appropriate to the type and / or phase of testing. For example, appropriate optical correction to achieve good visual acuity for a subject may be determined alternately in each eye, and then the two eyes stimulated together using a binocularly registered image, e.g., in such a way as to allow the subject to judge if both eyes see equally well, or if one of them is noticeably under-corrected compared to the other. For example, a test image may be broken into zones of features which together form a single image, at least some of which are presented only to one eye, and / or one eye at a time.

[0141] In some embodiments, lens power adjustments are under automatic control which allows automatic testing to be

[0142] An aspect of some embodiments of the present disclosure relates to providing cylindrical and axis correction to the optics of a subjective and / or objective visual acuity testing device. In some embodiments, the visual acuity testing device presents images using a scanning display device.

[0143] In some embodiments, the cylindrical and axis correction is provided together with a vision testing system configured for one or both of objective and subjective measurement of eye refraction; for example, to determine corrective lens prescriptions for eyeglasses and / or contact lenses. In some embodiments, a cylindrical refractive error correction unit is provided as an element of a virtual reality (VR) and / or augmented reality (AR) system.

[0144] A retinal scanning display (also known as a virtual retinal display, retinal scan display, or retinal projector) projects images onto the retina by the projection of suitably patterned light. Rather than relaying a conjugate image of a light source (e.g., a light source patterned with the scene of the image), such a display builds an image on the retina directly, by scanning a light source (e.g., one or more lasers) across the retina’s surface in a rapid, intensity modulated pattern. In effect, light from the beam source(s) is optically manipulated within the display so that it reaches the entrance pupil of the eye from different directions, rather than the single (generally fixed) each beam source actually occupies.

[0145] Accordingly, information about different angularly defined regions of the image scene is conveyed through beams arriving to the eye from those different angles. The image builds up over a period of time, but quickly enough that a single image is perceived. From whatever direction it arrives, the scanned beam reaches the entrance pupil of the eye. For design purposes, the entrance pupil is optionally considered as a circle or ellipse varying in the range of 2-6 mm in diameter, for example, about 2 mm, 3 mm, 4 mm, 5 mm, or 6 mm; though an actual eye entrance pupil is potentially smaller (e.g., in high lighting conditions) or larger (e.g., if medically dilated); e.g., in a range of 2-8 mm or 2-10 mm. The cornea and lens focus light entering the eye’s pupil from a single beam to a spot on the retina. Accordingly, production of such images is affected by optics of the eye itself in the usual ways, including spherical refraction error and cylindrical aberrations, such as are routinely corrected for using eyeglasses and contact lenses.

[0146] Although a retinal scanning display may internally create a “scanned beam” (the beam comprising all angles of the laser beam over the course of an image frame), if optical power corrections are applied to counteract flaws in the optics of the eye, they are applied chiefly to the laser beam itself, however it may be directed at any given moment. Put another way, the laser beam at each moment corresponds to a “pixel” which should be brought to optimal focus on the retina. In short, optical corrections are applied “intra-beam”.

[0147] Spherical error and / or cylindrical aberration are commonly corrected using personalized (optically static) corrective lenses. However, the use of certain optical systems (e.g., optometric testing systems) relies on being able to provide a range of such corrections. Potentially, certain virtual reality (VR) and / or augmented reality (AR) systems and / or users may benefit from such capabilities.

[0148] Concentrating on cylindrical correction, a basic arrangement for introducing an adjustable optical power and / or axis direction of cylindrical distortion to an optical system’s wavefront may rely simply on providing a plurality of cylindrically distorting lenses of different powers, with a lens of appropriate power being selected to replace any other lens in the system, e.g., manually, or by movement of a carousel. Cylinder axis may be selected in such a system by rotating the lens around the optical axis.

[0149] Another arrangement for introducing adjustable optical power and / or axis direction of cylindrical distortion comprises a plurality of lenses (e.g., a pair of lenses), arranged in directions which cross each other to a variable extent. For example, one lens may introduce negative optical power, and the other positive optical power. If each lens has the same magnitude, then when they are aligned there is minimal cylindrical power introduced (e.g., none of practical significance). When they are orthogonally placed, maximal cylindrical distortion is introduced. Intermediate levels of cylindrical distortion are introduced by intermediately oblique crossing angles. For a given selected cylindrical power, the cylinder axis direction may then be selected by rotating the crossed cylindrical lenses together by the same amount.

[0150] Accordingly, the crossing lenses may be positioned in an optical path to act effectively as a single variable-power cylindrical lens, providing a potential advantage by reducing a need to swap optical components. However, arrangements to introduce cylindrical distortion to an optical system potentially interact with spherical correction, in a manner which negatively affects calibrations and / or focusing of beams to pupils of the optical system. This may be the case particularly when the system is intended to function with one or both of spherical power and cylindrical power being varied. However, the inventors of the present disclosure have determined the existence of a class of optical arrangements which can reduce this issue sufficiently to potentially remove it as a limiting factor on overall device performance, while providing potential advantages for compactness and / or simplicity of device design and / or function.

[0151] Briefly, “vergence” is a property of a beam comprising non-parallel light rays. For beams overall (in geometrical optics, e.g., not necessarily considering wavelength dependent effects), vergence is defined in terms of the curvature of the beam’s optical wavefront, expressed as optical power (e.g., in diopters with a unit of m1). With increasing distance from an unmodified beam’s source, vergence approaches zero (flatness), similar to the way the local curvature of a sphere approaches flatness as the sphere gets larger and larger. Lenses in the optical path introduce changes to the wavefront curvature. For example, they may collimate it (reducing the vergence to near zero, or parallel), increase it, or decrease it. This can include switching vergence sign (e.g., switching a diverging beam to a converging beam). One convention for schematically depicting a beam along an optical path draws a path of at least one of its outer (marginal) rays. In such cases, the changing angle of the marginal ray(s) relative to the optical axis may be used as the measure of vergence.

[0152] Scanned beam optical systems such as retinal scanning displays produce “superimposed” vergences — one describing the wavefront curvature of an individual laser beam position (herein, the intra-beam vergence), and one describing the wavefront curvature of the collection of scanned beam positions (herein, the inter-beam vergence). In scanned beam optical systems, the presence of more than one vergence imposes design constraints affecting the beam’s condition at entrance and / or exit pupils — locations in the optical path which image the (physical) aperture stop. In a system intended to illuminate the retina of an eye, the relevant aperture stop which these pupils image may be the eye’s own (anatomical) pupil. Without suitable management of both laser beam (intra-beam) and scanned beam (inter-beam) vergences to converge at an illuminating optical system’s entrance pupil(s), illumination and / or some of the field of view is lost, degrading the beam that is actually able to enter the eye’s entrance pupil to form an image on the retina.

[0153] There is, in particular, a potential problem of introducing cylindrical correction intra-beam, without disturbing inter-beam relationships (e.g., without preventing focusing at the entrance pupil). For example, a cylindrical lens (including an arrangement of two or lenses which is or “acts as” as an adjustable cylindrical lens) can be placed in the optical path and create cylindrical correction effects on intra-beam vergence. But in many locations (e.g., locations away from an inter-beam pupil), this will also produce inter-beam vergence changes.

[0154] In some embodiments of the present invention, cylindrical correction is applied to the illumination beam of a retinal scanning display by placing two lens groups, each of one or more cylindrical lenses, in the optical path of the illumination beam. In some embodiments, the first and second lens groups are arranged to have (and preserve) a same shared cylinder axis, which in some embodiments is changeable (e.g., by rotation).

[0155] This allows differential effects on inter-beam vs intra-beam vergences to be produced. In some embodiments, the differential effects amount to a negligible change in inter-beam cylindrical vergence, but a significant (e.g., astigmatism-correcting) level of change in intra-beam cylindrical vergence. Since, in this case, inter-beam vergence magnitude is relatively small relative to overall beam width, differences in effects as a function of distance along the optical path are relatively negligible. For example, inter-beam vergence changes introduced by the first group encountered on the beam path can be effectively canceled by the second-encountered group (which may be of opposite diopter sign). To achieve cancellation, the two groups may have optical powers with the same diopter magnitude, or only slightly different. Optionally, the difference is selected to correct for the relatively small effects the of distance offset.

[0156] Accordingly, in some embodiments, one group is placed closer to an intra-beam waist and one group is further. Positions and strengths of the two lens groups are selected so that intra-beam vergence changes induced by the further of the cylindrical lens groups dominate (are larger than) vergence changes induced by the closer of the cylindrical lenses to introduce cylindrical distortion, but inter-beam vergence changes induced by the two groups is substantially diminished.

[0157] In some embodiments, the amount by which one lens group dominates the other is selectable to produce a magnitude of overall intrabeam cylinder vergence change reaching at least -8, -6, -5, -4, -3, or -2, negative diopters, and / or at least +2, +3, +4, +5, +6, or +8 positive diopters. Optionally, the same lenses are adjustable in position so that the magnitude of intrabeam cylinder vergence is continuously changed, or changed with steps at least as small as, for example, about 0.1, 0.125, 0.2, or 0.25 diopters. Optionally, at least 10 different magnitudes of overall intrabeam vergence change are selectable between maximum and minimum magnitudes. In some embodiments, both positive and negative overall vergence changes (e.g., in diopters) are selectable. In some embodiments, the overall selectable range in diopter change is at least 2, 4, 6, 8, 10, 12, or 16 diopters, including both positive and negative diopters.

[0158] In some embodiments, the first and second groups of one or more cylindrical lenses are of opposite diopter signs. Furthermore, in some embodiments, they are of similar magnitudes, e.g., similar within 50%, 25%, 10%, or 5%. In some embodiments, the first and second groups of one or more cylindrical lenses are placed on opposite sides of an intra-beam waist. Optical power may be divided among two or more lenses in one or both groups. The lenses within a group are optionally be arranged along an optical path section (e.g., a telecentric zone) so that together they approximate the effects of a single lens (a “virtual lens”) occupying a position between them.

[0159] In some embodiments of the present invention, cylindrical correction is applied using a system having the following features:

[0160] • At least two cylindrical lenses are provided.

[0161] • These lenses are configured to produce a net effect on intrabeam vergence, variable within a practical range of astigmatism encountered in optometry (e.g., -2 to 2 diopters, -3 to 3 diopters, -4 to 4 diopters, -6 to 6, or -8 to 8 diopters).

[0162] • However, there is also sufficient opposition of optical powers of the cylindrical lenses that net effects on inter-beam vergence are negated, at least to the extent that focusing light to the eye’s entrance pupil sufficient to display a complete test image is not significantly compromised.

[0163] In some embodiments, accordingly, there are provided a first at least one cylindrical lens and a second at least one cylindrical lens, wherein the at first and second cylindrical lenses (or lens groups) impose opposing vergence effects on the inter-beam vergence.

[0164] Regarding the phrase “not significantly compromised” used above with respect to pupil formation; “significant compromise” is optionally evaluated functionally, according to the performance of a subject undergoing testing for visual acuity. The performance should, in this case, not be adversely affected (compared to an actual or extrapolated “perfect” pupil). For example subject performance is not measurably, distinguishably, and adversely affected in terms of test accuracy, testing speed and / or (self-reported) subject comfort. Potential causes of performance degradation consequent to poor optical pupil formation (should it occur) include, for example: vignetting (relative darkening, e.g., of image edges), partial loss of test target visualization, difficulty in perceiving presented test targets, and / or difficulty in distinguishing differences in test targets among different conditions. in some embodiments, “not significantly compromised” is determined with respect to device parameters; the determination comprising, for example, one or more of the following criteria:

[0165] • The angular size of the test images shown to a subject fully subtends a specified region of interest (both vertically and horizontally) extending over at least 1° 2°, 3°, or 10°. The region of interest may be defined, for example, according to the test target size and / or resolution.

[0166] • The image display device may be considered as forming an optical pupil to the eye, typically by lens(es) that focus all beams to nearly the same location, each beam starting from approximately the same angle of incidence with the lens(es). In a system where the individual beams are almost parallel to each other or nearly parallel (for example a telecentric or nearly telecentric zone): after the converging lens, all beams will form the optical pupil at nearly the same position, with the diameter of the beams at this position defining the diameter of the optical pupil. When applying cylindrical power, the system can be viewed as having two optical pupils distributed along the optical axis, according to the effect of the cylindrical power on each axis. At one extreme is a first pupil is formed by beams shifted maximally by the varying cylindrical optical power. At the other is a second pupil formed by beams positioned where they are essentially unaffected by the chosen axis of cylindrical optical power — the “original” pupil position. If the positions of the two optical pupils do not sufficiently coincide, a larger-diameter pupil is then found at the “original” (without cylindrical corrective power) position of the optical pupil, since some beams (e.g., those most affected by the cylinder optical power) are displaced from their “home” pupil: fanning out from it, or yet to converge to it. Under these conditions, and throughout a range of optionally at least 2, 3, 4, 5 or more diopters of cylinder adjustment, a ratio of the optical pupil’s diameters (that is, its longest and shortest diameters, respectively along directions with and without cylindrical optical power distortions) remains less than about, for example, 3, 2.5, 2, 1.5 or 1.1.

[0167] • All parts of the test image region of interest provide maximal retinal illumination levels within at least 15% of a nominally sufficient average level for specified functioning of the device (e.g., visual testing, or other image presentation). Optionally, the threshold is at least 25%, 33% or 50%.

[0168] • Particularly for applications of embodiments for which image brightness is limiting (z.e., applications wherein reducing maximum brightness to achieve overall evenness reduces an aspect of usability), the maximum brightness in the brightest illuminable regions is no more than 50% brighter than the maximum brightness in the dimmest illuminable regions. This may be understood as a measure of how much illumination compensation is needed to overcome flaws in optical pupil formation.

[0169] Disturbance of intra-beam vergence is potentially minimized by placing the cylindrical lens where the laser beam for each position of the larger scanned beam has its waist (that is, its narrowest point between two wider regions).

[0170] For example, when placing a cylindrical lens having focal length F2after a spherical lens of focal length F15the focus point changes in each axis according to the power of the lenses in that axis, and the distance between them. As the cylindrical lens has power in a single axis, that axis is modified; the other axis remains unaffected. Rotating the cylindrical lens allows choosing the affected axis.

[0171] Modifying the distance D between the lenses changes the focus point FTof the affected axis in accordance with Equation 1 :

[0172] The distance of the “new focus” from the second lens is the back focus length (BFL), described in Equation 2:

[0173] Accordingly: when the distance between the lenses (£)) approaches focal length F15BFL = 0. In this position the vergence of the beam is not affected; only its width.

[0174] If a third lens is placed after the focus point of the two-lens system described above at a distance from the focus point of the unaffected axis that is equal to its own focus length, the light beam will be collimated on that axis, but not on the axis chosen to position the cylindrical lens when BFL 0. This allows modifying the vergence at a chosen axis by rotating the lens.

[0175] Cylinder correction introduced to the illumination path of a scanning display potentially enables its use in optometric testing of visual acuity and / or eye refractive error, for example, as detailed in relation to Figures 8-15, herein. In some embodiments, built-in cylinder correction may enable users of retinal scanning display devices used for general display purposes to obtain a clear image without necessarily having to use other corrective lenses (e.g., their usual eyewear), with potential benefits for device size and / or wearing comfort (e.g., less need to make room for wearing eyeglasses together with the device).

[0176] In some embodiments, cylindrical corrective lens is used which is intrinsically adjustable in optical power and / or axis (an adaptive lens); for example, a liquid lens and / or liquid crystal lens. Such a lens is optionally placed at an optical pupil of the optical system, where it potentially has a selective effect on intrabeam vergence. Embodiments herein are optionally used with an arrangement of this sort, insofar as they are not explicitly limited to use of another arrangement for providing cylindrical correction. For example, a cylindrical correction unit 214 generally may be implemented using such an arrangement (perhaps substituted for the arrangement of another implementation described herein), and optionally moved to a more suitable location in the optical path (e.g., an optical pupil) as appropriate. It is anticipated that during the lifetime of patent(s) potentially maturing from this application, new relevant forms of intrinsically adjustable lenses will be developed, including and / or other than those referred to herein as liquid lenses and / or liquid crystal lenses. The term “intrinsically adjustable lens” is intended to include all such new technologies a priori.

[0177] Although embodiments of the present disclosure are described in particular in relation to retinal scanning displays, it should be understood that other display types (particularly miniaturized display types) are optically used; e.g., replacing the retinal scanning display laser and MEMS mirror, and suitably coupled into the rest of the system using appropriate adaptor optics. A hallmark of a highly miniaturized display may be its ability to produce and form an image and / or image beam from a source contained within a volume having an optical cross-section (perpendicular to the optical path) of about 10 cm2or less, 6.5 cm2or less, 4 cm2or less, or 1 cm2or less. However, a less miniaturized display is optionally used in some embodiments of the present disclosure.

[0178] For example, in some embodiments, a micro LED (also known as mLED or pLED) display replaces one or more image beam generating elements in any of Figures 1A-20C, with adapting optics provided as appropriate. In some embodiments (e.g., embodiments implementing aspects of these figures), another display technology is used; for example, pOLED, LED, OLED, QDLED, LCD, LCDS, DLP, or another technology. It is anticipated that during the lifetime of patent(s) potentially maturing from this application, new relevant forms of miniaturized display technologies will be developed and / or become available on the market, including and / or other than those mentioned herein. The term “display” is intended to include all such new technologies a priori.

[0179] Before explaining at least one embodiment of the present disclosure in detail, it is to be understood that the present disclosure is not necessarily limited in its application to the details of construction and the arrangement of the components and / or methods set forth in the following description and / or illustrated in the drawings and / or given in the Examples, drawings. Features described in the current disclosure, including features of the invention, are capable of other embodiments or of being practiced or carried out in various ways.

[0180] Cylindrical Correction

[0181] Reference is now made to Figure 1A, which schematically illustrates a cylindrical refractive error correction unit, according to some embodiments of the present disclosure.

[0182] In some embodiments, a cylindrical lens arrangement comprises two cylindrical lenses 6, 8 within a telecentric zone 10 established by two lenses 2, 4. Individual beams, however, are not collimated in zone 10.

[0183] The image eventually projected onto by the retina is generated by light source 20 on the left side of the drawing. Implementation details of this light source are not shown in Figure 1A, but may be implemented, e.g., as described in relation to any of Figures 8-15 herein, for example as a scanning retinal display, or another type of display (e.g., incorporating changes, for example as described in relation to Figure 5B). Embodiments of Figure 1A are optionally provided with embodiments of these figures, e.g. , as implementations of a cylindrical correction unit 214. Beyond exit pupil position 14 at the right side of the drawing, the light is eventually relayed via further optics of the optometric testing device to the patient’s own pupil and retina, e.g., to perform a subjective vision acuity test.

[0184] Selected individual laser beams 1A-1C are each drawn as three non-parallel lines (rays) representing the width (the outer or “marginal” rays) and centerline of the laser beam at different distances. Waist position 15 indicates the location of the narrowest region of the beams 1A-1C along the length of the telecentric zone. For the whole image to be seen by the patient, beams 1A- 1C should overlap with the centerline beam within the area of the exit pupil at exit pupil position 14 (and also again at the patient’s own pupil).

[0185] In some embodiments, light source 20 comprises a laser and one or more scanning mirrors. It operates by rapidly scanning laser beams in a 2-D pattern that angles outward to fill collimating lens 2. For purposes of explanation, the beams are depicted as arriving at angles which collimating lens 2 makes parallel, creating the telecentric zone 10. This could be varied somewhat to change the spherical corrective refractive power. Optionally, spherical correction is applied by separate optics, e.g., as described in relation to Figures 8-15 herein.

[0186] To provide variable orientation of cylindrical refraction, cylindrical lenses 6, 8 can rotate around the optical axis to change the orientation of the cylindrical correction. To provide variable refractive power, at least one of the cylindrical lenses 6, 8 (lens 6 in the embodiment shown) is moveable along the optical axis. This changes the corrective cylindrical refractive power applied to the image which the patient sees. With greater distance of a cylindrical lens from waist position 15, a larger correction is imposed. In some embodiments, cylindrical lenses 6, 8 are mutually aligned in their respective cylindrical axes; e.g., exactly aligned, or aligned at least to within 5°, 3°, or 1° of each other. These values in degrees should also be understood be available (without limitation) to other examples of mutually aligned cylindrical axes described herein, changed as appropriate, unless incompatible or otherwise stated.

[0187] As also discussed in the overview, providing a second cylindrical lens has potential advantages, because there are two different “vergences” which must be co-managed along the optical pathway. For example, at each position of its scanning pattern, the rays of a laser beam may begin approximately parallel (collimated, corresponding to a low intra-beam vergence). However, the beams at different positions of the scanning pattern are spread-angled compared to each other (diverging, e.g., “negative” inter-beam vergence). Both vergences, existing inside the same overall system, are changed in different ways by the lenses the beam encounters. In particular, the intra- beam vergence is not parallel (not collimated) in telecentric zone 10, as illustrated by the crossing lines defining each laser beam 1A-1C, including its waist position 15. The inter-beam vergence, in contrast, is parallel or nearly parallel.

[0188] The position of single cylindrical lens 6 in telecentric zone 10 modifies both vergences. Changing the intra-beam vergence gives the desired effects on optical power in a chosen axis. Changing the inter-beam vergence, however, has an effect on convergence at the exit pupil, which could prevent some of the beams from entering the subject’s pupil.

[0189] By introducing counter-refracting lens 8 with a refractive power opposite to that of lens 6, the actual overall effect on inter-beam convergence is potentially greatly diminished. For example, lens 8 introduces non-parallel inter-beam vergence which is largely canceled a short distance later by lens 6. Beginning from this arrangement, if the distance through which lens 6 moves when modifying the cylindrical power is kept short, the exit pupil size at exit pupil position 14 will not change significantly; that is, near-cancellation of inter-beam vergence happens throughout a relatively large range of lens positions.

[0190] This allows the two rotationally aligned lenses 6, 8 to have nearly the same effect in positions throughout telecentric zone 10. In contrast, the lens effects on intra-beam vergence are highly dependent on distance from waist position 15, since moving a lens closer to waist position 15 proportionally weakens its effect on cylindrical correction. In some embodiments, this module or unit for optical cylinder correction comprises, a device for introducing cylindrical correction to one or more scanned laser beams, comprising two rotatable cylindrical refractive units (e.g., single lenses, or groups of lenses) positioned in a telecentric zone of an optical system. At least one of the units is movable along an axis of the telecentric zone to produce a variable net effect on intra-beam vergence. The cylinder axes of the two units are similarly oriented, and have complementary optical powers selected to largely cancel out each other’s effects on inter-beam vergence.

[0191] In some embodiments, the one or more scanned laser beams are used in a retinal scanning display system.

[0192] In some embodiments, moreover, the scanned laser beams are produced as part of the illumination system of an optometric device incorporating both objective and subjective refractive error visual acuity testing capabilities (e.g., testing for eyeglasses prescriptions). At least the subjective test makes use of the portion of the optical pathway incorporating the two cylindrical refractive units. For example, in a subjective test, the retinal scanning display produces a target image, and cylindrical correction is adjusted until the target is seen clearly according to patient reporting. In an objective test using the same device, the retinal scanning display may be used to produce a target image, which is used to guide the direction and distance of visual focus (subject accommodation), while optics in another part of the system provide test illumination and measurement functions.

[0193] It should be noted that the optical elements described from lens 2 to lens 4 (and in particular, the optical subsystem of lenses 6, 8) are operable with any suitable source of illumination, so long as lens 2 (or another arrangement of optics) interacts with the beam that arrives at it so as to generally maintain the position of the exit pupil of the system. For example, the magnitude of the inter-beam vergence is reduced sufficiently to allow differential introduction of cylinder correction, while preserving beam entrance to the pupil of the subject’s eye. In some embodiments, this comprises the projected image which then reaches the retina being seen without disturbance to testing results, e.g., due to vignetting or loss of field of view of the projected image. The optical elements including lenses 6, 8 may be provided after a previous relay section of the optical path, after folding mirrors, after beam splitters, or a part of another suitable arrangement of optical elements which interact with the illumination beam.

[0194] Reference is now made to Figure IB, which schematically illustrates a cylindrical refractive error correction unit, according to some embodiments of the present disclosure. Except as next noted, the elements shown in Figure IB generally correspond to elements of Figure 1A, and embodiments according to Figure IB may be used to provide cylinder correction to optical systems also as described in relation to Figure 1A.

[0195] In some embodiments, the net refractive power of cylindrical lens 8 (of Figure I A) is divided among two or more lenses 8A, 8B, one on either side of cylindrical lens 6. Lenses 8A, 8B are positioned to allow the overall net cylindrical refractive power (also including lens 6) to be changed from positive to negative diopters, optionally while moving a single lens. Dividing potentially enables this because with suitable selection of lenses, the “average” position of lenses 8A, 8B may be placed optically nearer to the middle of telecentric zone 10 than lens 8 is (e.g., on the right side of the waist position 15), although no physical lens is actually there. Accordingly, cylindrical lens 6 can be moved to either side of that position.

[0196] Reference is now made to Figures 2A-2B, which schematically illustrate pupil effects of the introduction of cylindrical correction in one- and two-lens cylindrical correction units, according to some embodiments of the present disclosure.

[0197] The pupil effects are simulated for optical systems defined as follows. In both of Figures 2A and 2B, shaded area represents a nominal 4 mm diameter pupil. In the examples shown, the system is designed for optimal pupil at a cylinder correction of -2 cylinders. Pupil dispersion (pupil size) results shown are for cylinder corrections on either side of this value by ±2 diopters. For the sake of illustration, a 1:1 relay is assumed. Effects on pupil dispersion potentially increase as the magnification power of the relay is increased, which is expected to be the case at least for a scanning retinal display. For example, in some embodiments, relay magnification in the range of 1:1 to 1:8 is used; e.g., a 1:1.5, 1:2, 1:3, 1:4 1:5, 1:8 or other relay magnification factor is used. These numbers optionally apply to any of the embodiments described herein.

[0198] In Figure 2A, just a single cylinder lens is used to introduce cylindrical aberration to the wavefront (e.g., equivalent to lens 6 of Figure 1A without providing lens 8), with a power of 8 diopters.

[0199] In Figure 2B, two opposing-sign cylinder lenses are used to introduce cylindrical aberration to the wavefront (e.g., equivalent to both of lenses 6 and 8 of Figure I A), with powers of 8 diopters (moving) and -10 diopters (stationary).

[0200] Accordingly, regions 251A-251C (Figure 2A) and region 251 (Figure 2B) represent beams dispersal by the introduction of cylinder correction of -4 diopters. Regions 252A-252C (Figure 2A) and region 252 (Figure 2B) represent beam dispersal by the introduction of cylinder correction of 0 diopters. In Figure 2A, beam crescents falling outside of shaded area 412 (e.g., for regions 251A, 251C, 252A, 252C represent lost light, with consequent degradation of image quality.

[0201] In Figure 2B, dispersals of the beams are indistinguishable, and so each condition is represented by one region (regions 251 and 252) only. There is no loss of light at the pupil due to pupil dispersion.

[0202] As mentioned, larger cylindrical corrections and / or larger magnifications by the relay will tend to exaggerate effects, e.g., to the point that some beams may fail to enter the pupil 412 at all in the single-cylinder correction mode. It may be noted that there is no horizontal dispersion, since cylindrical correction is only applied along one axis. Optionally, this allows the orthogonal axis to the axis of maximum dispersion to be used as a reference for evaluating the magnitude of pupil dispersion under various conditions.

[0203] Reference is now made to Figures 3A-3B, which schematically illustrates an optical system 101 comprising subjective and objective testing optical subsystems, according to some embodiments of the present disclosure. In this embodiment, light source 20 also acts as an objective test illumination source 200. It is optically operated together with subjective pathway illumination activated for use as a focusing and / or accommodation relief target by the subject.

[0204] Elements 20, 2, 8A, 6, 8B, and 4 correspond to the designations shown for the adjustable cylinder correction unit of Figure IB, comprising a cylindrical correction unit 214, for example as described in relation to Figures 8-15, herein.

[0205] Beam splitting optics 300, lens 402, optional folding mirror 404, collimating optics 204, beam splitter 406, beam combiner 408, objective test detection unit 102, relay lens 400, folding mirror 502, relay lens 500 eye 108, eye pupil 412, and retina 110 correspond to same-numbered elements described in relation to Figures 8-15 herein; noting, however, that relay lens 400 is shown here after beam splitting optics 300, its role in collimating the objective light path being taken over by collimating lens 2 of the cylinder correction unit.

[0206] Reference is now made to Figure 4, which schematically illustrates an optical system 101 providing a separate objective testing illumination source 200, according to some embodiments of the present disclosure.

[0207] Several elements of the subjective illumination optical path remain as for Figures 3A-3B, including elements 20, 2, 8A, 6, 8B and 4 of the cylindrical correction unit 214, except that light source 20 does not provide an objective test illumination source. Relay lenses 400, 500 and folding mirror 502 are also shown again. Scale bar 550 indicates approximate sizes of the optical arrangements of Figure 4. As an example, arrangements in other embodiments may be understood, in some embodiments, to be scaled similarly; e.g. with the beam envelope in telecentric regions of beam paths being about 2 cm wide. These measurements are non-limiting. It is readily understood to a person of ordinary skill in the art that particular lens powers, folding mirror arrangements, telecentric zone lengths, focal lengths, and other parameters of the system are optionally varied in suitable relationships to maintain the overall functional relationships of optical elements to each other, and functionality of the optical system overall, e.g. as descried herein. Examples of focal lengths of lenses, for example, may be estimated from pupils and / or focus points illustrated in the various drawings.

[0208] Objective testing is performed through an optical pathway wherein a beam from objective testing illumination source 200 impinges on beam splitter 301, is directed toward the eye through beam combiner elements 408A, 408B (corresponding to beam combiner 408 of other embodiments), and then to eye pupil 412 and retina 110 of eye 108. Returning light passes through beam splitter 301 and relay lenses 402, 401 to reach detection unit 102.

[0209] It should be noted that the arrangement of beam combiner elements 408A, 408B leaves open an unobstructed light path leading straight from eye 108. In some embodiments, beam combiner element 408B is provided as a partially reflective mirror, allowing light from straight beyond it to be combined as well. In some embodiments, a beam is brought into beam combiner element 408B configured to produce a focused image on the retina of the scene beyond the optics, e.g., using a suitable arrangement of one or more prisms, optionally comprising lenses and / or mirrors. A potential advantage of this is that the subject can be asked to look into the distance of their actual surroundings to encourage lens accommodation, and or eye positioning. Relative illumination from the scene and / or device-internal illumination (e.g., the subjective test target beam) can be adjusted as appropriate to provide suitable visual contrast to allow simultaneous viewing of each. Optionally, test targets are presented in such a way (e.g., with suitable focus and optionally with a suitable binocular eye vergence so as to produce a binocularly registered image) that the subject perceives a testing target as present in the scene at a particular distance. Optionally — for example, when testing a child or uncommunicative subject — the tester can use the surrounding pass-through to present any available and attention-attracting physical object at any distance available within the testing space to assist the testing process.

[0210] In some embodiments, additionally or alternatively, passthrough through combiner element 408B is used to incorporate a light beam originating from an additional display device: for example an integrated display screen, and / or a larger display screen set up in the surroundings. This has potential advantages, e.g., to allow a remotely-supervised testing session, in which the subject wearing the device is able to see and optionally interact with a testing supervisor (examiner) who is telecommunicating through the screen. The testing supervisor optionally gives all needed assistance to the subject through the telecommunication link. Optionally, there is an on-site assistant (technician) who assists in some portions of arrangements. Optionally, the testing supervisor supervises more than one test at a time, e.g. giving group and / or individual instructions during a telecommunication session involving a plurality of subjects and testing devices, wherein both one-to-one and group interaction is enabled, according to the needs of the moment and / or the particulars of the local telecommunication equipment configuration. The test presented may comprise objective and / or subjective visual acuity testing, in any suitable order of test presentation, and optionally with subjective and objective testing occurring at least in part simultaneously.

[0211] With adjustments to their optics as appropriate, a surroundings and / or auxiliary display pass-through arrangement is optionally provided together with any of the other embodiments presented herein.

[0212] Additional details regarding functionality for various components and / or subsystems of Figures 3A-4 are described in relation to remaining figures herein, including embodiments described in relation to Figures 6-20C.

[0213] Combined Cylindrical and Spherical Correction

[0214] Reference is now made to Figure 5A, which schematically illustrates a cylindrical refractive error correction unit 214 in combination with a spherical refractive error correction unit 218, according to some embodiments of the present disclosure.

[0215] Details of the cylindrical refractive error correction unit 214 include lenses 2, 4, 6, 8 configured, in this example, as described in relation to Figure 1A; however, this example should not be considered limiting.

[0216] Also shown are relay lenses 400, 500; and eye 108 comprising retina 110 and anatomical pupil 412.

[0217] Within spherical correction unit 218 are shown two fixed mirrors 522, 523 within the main beam path, and a pair of moving mirrors 521, which reflect light diverted from the initial direction of the beam path at mirror 522 back onto mirror 523, from where the light continues on to relay lens 500.

[0218] Moving mirrors 521 move toward or away from mirrors 522, 523, lengthening or shortening the overall beam path. This in turn adjusts spherical aberration of individual beams, e.g, it changes whether they come to a focus at, before, or after the position of retina 110. Since the beams are collimated to each other, the overall beam envelope does not change as a result of adjustments to the position of moving mirrors 521.

[0219] Screen Illumination Sources

[0220] Reference is now made to Figure 5B, which schematically illustrates a cylindrical refractive error correction unit 214 in combination with a screen illumination source 20A, according to some embodiments of the present disclosure. In some embodiments, the screen is a display panel; for example using pLED,kl pOLED, OLED, QDLED, LCD or another display technology.

[0221] The functions of lenses 4, 6, and 8, in this example, remain as described in relation to other embodiments providing cylindrical aberration correction, with pupil 14 being formed beyond relay lens 4, and conjugate to pupil 412 formed at eye 108 after passing through the relay formed by relay lenses 400, 500. Also shown is retina 110, on which an image of screen 20A is formed during optical acuity testing.

[0222] Since screen illumination source 20A is initially extended spatially, it may be considered as performing the roles of both light source 20 and relay lens 2 as described in relation to Figure 1A. The spread of the light from each pixel of screen illumination source 20A may be angularly wider than shown; just the envelope of light paths that pass through pupil 14 is shown. Adjusting the position of screen illumination source 20A along the optical axis acts to adjust spherical corrective refractive power, e.g., performing the function of the movement of moving mirrors 521 in Figure 5 A.

[0223] Eye Refraction Testing Systems

[0224] Reference is now made to Figure 6, which schematically illustrates a block diagram of an optical system 101 combining objective and subjective eye refraction testing subsystems, according to some embodiments of the present disclosure.

[0225] In some embodiments, subjective testing and objective testing optical subsystems of optical system 101 share combined use of a retinal scanning display used to produce test images. In some embodiments, optical system 101 includes objective illumination unit 100 (which produces illumination reflected and measured for determining objective test results), an objective test detection unit 102 (which performs detection of the reflected objective illumination light), a subjective illumination unit 104, and a scanning unit 106. Optionally, scanning unit 106 comprises a scanning mirror such as a MEMS (micro electromechanical system) mirror, galvo mirror or other reflective or transparent element used to produce beam scanning. For use in objective measurement, the objective illumination unit 100 illuminates the subject’s eye 108. Light reflected by a layer in the subject’s eye 108 returns in part to the objective test detection unit 102. The reflected light reaching the objective test detection unit 102 contains refractive information from the subject’s eye 108. For subjective measurement, the subjective illumination unit 104 emits one or more beams (e.g., beams of different colors) which are two-dimensionally scanned ( / '.<?., deflected to different angles which change rapidly in time so as to produce the impression of a single image) by scanning unit 106. The scanned light enters the subject’s eye 108 and creates an image on the subject’s retina 110. Optionally, the subjective illumination unit 104 and scanning unit 106 are used to form images (focused or unfocused) used to fixate the gaze and / or control lens accommodation (e.g., accommodation relief) of the subject eye 108 during objective testing.

[0226] Optionally, optical system 101 includes a keratometry unit 112. Keratometry unit 112 is configured to measure corneal shape of the subject’s eye(s). This allows acquiring further and / or confirming information regarding optical functioning of the subject’s eye 108; for example: regarding astigmatism, astigmatism axis and / or total corneal power, and / or the cornea’s radius of curvature.

[0227] Reference is now made to Figure 7, which schematically illustrates a block diagram of a variant of optical system 101 combining objective and subjective eye refraction testing subsystems, and having a dual-use scanning unit 106, according to some embodiments of the present disclosure.

[0228] The optical system 101 of Figure 7 also includes objective illumination unit 100, objective test detection unit 102, subjective illumination unit 104 and a scanning unit 106. In this example, one or more beams emitted from the objective illumination unit 100 are directed by scanning unit 106 to the subject’s eye 108, with the location of impingement and / or angle of incidence on eye 108 being affected by the position of scanning unit 106.

[0229] A portion of the light is then reflected by a layer in the subject’s eye 108 to the objective test detection unit 102. The reflected light reaching the objective test detection unit 102 contains refractive information from the subject’s eye 108.

[0230] As before, the subjective illumination unit 104 emits one or more beams which are two- dimensionally scanned, also by scanning unit 106. The scanned light enters the subject’s eye 108 and creates an image on the subject’s retina 110. Optionally, the subjective illumination unit 104 and scanning unit 106 are used to form images (focused or unfocused) used to fixate the gaze and / or control lens accommodation (e.g., accommodation relief) of the subject eye 108 during objective testing. Light from the two sources may be presented simultaneously (e.g., where light from objective illumination unit 100 and subjective illumination unit 104 may be separable by a property such as wavelength and / or polarization to avoid interference with the function of objective test detection unit 102), or optionally presented in rapid alternation.

[0231] Optionally, optical system 101 includes a keratometry unit 112. Keratometry unit 112 is configured to measure corneal shape of the subject’s eye(s). This allows acquiring further and / or confirming information regarding optical functioning of the subject’s eye 108; for example: regarding astigmatism, astigmatism axis and / or total corneal power, and / or the cornea’s radius of curvature.

[0232] Optical Modules of Eye Refraction Testing Systems

[0233] Reference is now made to Figure 8, which schematically illustrates a block diagram illustrating optical modules of a variant of optical system 101 combining objective and subjective eye refraction testing subsystems, and having a dual-use scanning unit 106, according to some embodiments of the present disclosure. In some embodiments, optical system 101 of Figure 8 corresponds to a more modularly detailed illustration of optical system 101 of Figure 7. In particular, indication of certain optionally common units is shown, along with certain modular details of correction and relay optics.

[0234] In some embodiments, objective illumination unit 100 itself comprises an objective beam source 200 and associated collimating and focusing optics 202.

[0235] The beam source 200 comprises, for example, one or more light emitting diodes and / or laser diodes such as edge emitters or VCSELs in the IR range (>640 nm). Optionally, beam source 200 produces light in another wavelength range, e.g., in the visible or UV range.

[0236] Collimating and focusing optics 202 comprise, for example, one or more lenses (spherical and / or cylindrical), configured to focus and / or collimate the beam emitted from beam source 200. Collimating and / or focusing optics 202 optionally include a constant or variable-diameter pin hole.

[0237] Scanning unit 106 and collimating optics 204, in some embodiments, form a functional group of modules shaping and transmitting the beam from objective illumination unit 100 toward the eye. Collimating optics 204 comprises, for example, one or more lenses, of which one or more is moveable along the optical axis of this beam. Additionally or alternatively, collimating optics 204 comprises one or more tunable lenses; for example, lenses that change focus by electrically controlling the curvature of a meniscus between two immiscible liquids, and / or change focus by another means.

[0238] From collimating optics 204, the beam from objective illumination unit 100 transmits to optics-to-eye 206, optically configured to direct the beam to the subject’s eye 108. For example, optics-to-eye 206 comprises one or more lenses and / or folding mirrors. Optionally, optics-to-eye 206 includes one or more optical elements which combine or separate beams. In some embodiments, these include an optical element (e.g., a dichroic beam splitter) that allows light to pass through or be reflected from it depending on the light’s wavelength. For example, it is optionally configured to let IR light pass, while reflecting visible light. Optionally, it is configured to reflect a portion of the IR light, but let another portion pass, e.g., so that that light can pass through it to the eye, but then (upon returning from the eye), be diverted at least in part (and preferably mostly, e.g., at least 50%, 60%, 70%, 80%, 90% of returning light) to a detector. Additionally or alternatively, there is provided an optical element having refraction properties sensitive to polarization. For example, light polarized in s-polarization refracts from this element differently than light polarized in p-polarization. In some embodiments, there is provided a diffractive optical element such as a diffractive beam combiner or splitter, or an optical wave guide. The splitting / combining elements are arranged to suitably direct light from the different sources of optical system 101 to eye 108, and / or direct light reflected from eye 108 to an appropriate detector, e.g., objective test detection unit 102.

[0239] Objective test detection unit 102 is configured to detect reflection from the subject’s eye 108; and in particular, light received by the subject’s eye 108 from objective illumination unit 100. In some embodiments, the detector of objective test detection unit 102 comprises one or more photo diodes, a CCD camera, a PSD (Position Sensitive Detector) and / or another photosensor. Optionally, objective test detection unit 102 comprises optics configured to compensate (at least approximately) for the refractive power of the subject’s eye 108, and to focus the image of the retina 110 onto the detector. Examples include: a moveable and / or tunable lens positioned before the detector, detector and lens configured as a movable unit relative to a lens placed between them and the subject’s eye 108, and a moveable or tunable lens placed between the subject’s eye 108 and the lens and detector unit.

[0240] In some embodiments, the subjective testing optical subsystem defines an optical pathway including a subjective illumination unit 104 comprising a subjective testing beam source 210 and combining and collimating optics 212. Beam source 210 comprises, for example, one or more laser diodes (e.g., edge emitters or VCSELs), emitting in the visible range (440-660). Preferably the beam source 210 includes at least three beam sources: a red beam source (e.g., wavelength approximately between 620 nm to 660 nm), a green beam source (e.g.. wavelength approximately between 500 nm to 540 nm), and a blue beam source (e.g.. wavelength approximately between 440 nm to 470 nm). combining and collimating optics 212 comprise, for example, one or more optical elements to combine beams. For example, combining and collimating optics 212 comprises one or more of:

[0241] • An optical element that allows light to pass or be reflected depending on the light’ s wavelength.

[0242] • A diffractive optical element such as a diffractive beam combiner.

[0243] • An optical wave guide, for example, on a photonic integrated circuit.

[0244] Combining of the beams is optionally before or after being collimated by one or more collimating lenses. Where beams of multiple wavelengths are to travel together, they are preferably combined so as to match their vergences. Combining and collimating optics 212 optionally includes a pin hole.

[0245] In some embodiments, cylindrical correction unit 214 (wherever it is placed) corresponds to an arrangement of lenses operable to introduce a selected axis and power of cylindrical optical correction to the beam subjective illumination unit 104; for example, as described in relation to Figures 1A-2B.

[0246] Alternatively, in some embodiments, there are provided one or more chambers, providing among them for a plurality of cylindrical lens powers to be introduced into the beam. Optionally, each of a plurality of chambers is selectable by rotation (or exchanging motion), to introduce a different cylindrical lens power. Additionally or alternatively, one or more chambers is provided with Jackson’s cross cylinder lenses, adjustable relative to each other to introduce a range of different cylindrical lens powers. Selection and / or adjustment sets the current optical power compensating for the subject’s cylindrical and axis error.

[0247] The location of cylindrical correction unit 214 within the optical path is not necessarily in the same order as shown with respect to scan unit 106, subjective relay optics 216 and / or spherical correction unit 218. For example, it may generally be rearranged in a position also as described with respect to spherical correction unit 218, before or after it. It is a potential advantage in particular to place cylindrical correction unit 214 after scan unit 106, as this avoids complicating the cylindrical correction with wavefront effects caused by the varying angles of reflection from the mirror. This applies also to correction unit 214 as shown and discussed in relation to other figures, for example, Figures 9 and 12. In some embodiments, scanning unit 106 is shared between the subjective testing and objective testing optical subsystems of optical system 101.

[0248] Subjective relay optics 216 comprises, for example, one or more lenses that relay the beam from scanning unit 106 to a chosen plane; for example, to the subject’s pupil, with a chosen magnification. Alternatively, the beam is relayed with a chosen magnification to an intermediate plane before further relay to the subject’s pupil.

[0249] Spherical correction unit 218, in some embodiments, comprises, for example, a moveable and / or tunable lens that moves along the optical axis of the laser beam from subjective illumination unit 104. It is shown placed in the optical path after subjective relay optics 216. Alternatively, it may be positioned between the beam source 210 and the scanning unit 106 (e.g., as for cylindrical correction unit 214). In another example, spherical correction unit 218 optionally comprises one or more movable mirrors and / or lenses placed between the lenses of the subjective relay optics 216.

[0250] In the position shown, spherical correction unit 218 includes optics which direct light to optics-to-eye 206. Within optics-to-eye 206, some elements are optionally shared in common with optical path(s) of the objective testing optical subsystem. For example, a beam combiner and / or folding mirrors may be shared. Other elements may have functions used by only one of the testing functions, for example, folding mirrors and / or lenses.

[0251] In some embodiments, along light paths(s) of the objective testing optical subsystem: a beam emitted from the objective beam source 200 is collimated and / or focused by collimating and focusing optics 202. This beam is then reflected by scanning unit 106 to collimating optics 204, which together with scan unit 106, control, for example, the beam’s location and / or angle of impingement onto the subject’s eye 108 after passing through optics to the eye 206. Light reflected from a layer in the subject’s eye returns to optics-to-eye 206, and is then reflected to objective test detection unit 102. The reflected light reaching the objective test detection unit 102 contains refractive information from the subject’s eye 108, which is subjected to further analysis, e.g., according to methods of objective refraction measurement known in the art.

[0252] In some embodiments, along light paths(s) of the subjective testing optical subsystem: one or more beams emitted from the subjective beam source 210 are collimated / combined by combining and collimating optics 212. The one or more beams pass through cylindrical correction unit 214 and are two-dimensionally scanned by scanning unit 106. Cylindrical correction unit 214 is not necessarily at this location; e.g., optionally it is positioned just before or after spherical correction unit 218, or at another location after scanning unit 106. Subjective relay optics 216 relay the scanned beams to a chosen plane; for example, the subject’s pupil. The scanned beams pass through the spherical correction unit 218 and optics-to-eye 206. The scanned light enters the subject’s eye 108 and creates an image on the subject’s retina 110. During subjective visual acuity testing, the visual appearance of the image is reported by the subject. Settings of spherical correction unit 218 and / or cylindrical correction unit 214 are adjusted accordingly to determine settings that produce the reported best image according to the reported perceptions of the subject.

[0253] Reference is now made to Figure 9, which schematically illustrates a block diagram illustrating optical modules of a variant of optical system 101 combining objective and subjective eye refraction testing subsystems, having a dual-use scanning unit 106, according to some embodiments of the present disclosure. In some embodiments, optical system 101 of Figure 9 corresponds to a variation of optical system 101 of Figures 7 and 8. In particular (compared to Figure 8), indication of objective relay optics 302 and beam splitting optics 300 is shown. The modules added in Figure 9 compared to Figure 8 assist support for objective refractive error measurement based on the Scheiner principle (e.g. , as described in relation to Figures 10-11). Also shown are boxed indications identifying modules of the objective testing optical subsystem (box 954), the subjective testing optical subsystem (box 952), and modules common to each (box 956).

[0254] In some embodiments, the objective testing optical subsystem of optical system 101 comprises an objective illumination unit 100, including beam source 200 and collimating and focusing optics 202. Also included is scanning unit 106. Beam splitting optics 300 comprise one or more optical elements configured to separate beams; for example, an optical element that allows light to pass or be reflected depending on the light’s wavelength. In some embodiments, such an optical element is configured to let IR light pass, while reflecting shorter-wavelength visible light. In some embodiments, the optical element has refraction properties sensitive to polarization. For example, it refracts s-polarized light differently than p-polarized light. In some embodiments, the beam splitting optics comprise a diffractive optical element; for example, a diffractive beam splitter.

[0255] Objective relay optics 302 comprise, for example, two or more lenses which relay the beam from scanning unit 106 to a chosen plane such as the subject’s cornea, retina 110, or other chosen plane in the eye; and with a chosen magnification. Also provided are collimating optics 204, optics- to-eye 206, and objective test detection unit 102, configured to detect reflection from the subject’s eye 108.

[0256] In some embodiments, the subjective testing optical subsystem of optical system 101 comprises a subjective illumination unit 104, including beam source 210 and combining / collimating optics 212. Also provided, in some embodiments, are cylindrical correction unit 214 (again, not necessarily at this location; e.g., optionally just before or after spherical correction unit 218 or at another position after scanning unit 106), scanning unit 106 (shared in common with the objective testing optical subsystem), beam splitting optics 300 (also shared in common), subjective relay optics 216, spherical correction unit 218 and optics-to-eye 206 (again, shared in common).

[0257] Some elements of modules shared in common may be individually assigned to just one of the two testing subsystems. For example, there may be a common beam combiner, but one or more lenses, folding mirrors or other elements separate.

[0258] Reference is now made to Figure 10, which is a schematic optical diagram of the objective testing optical subsystem of optical system 101 of Figure 9, according to some embodiments of the present disclosure.

[0259] In some embodiments, beam source 200 emits a beam which focusing optics 202 changes the diameter of, approximately focuses onto a scanning unit 106. Scanning unit 106 reflects the beam to optional folding mirror 404 through lenses 400 and 402, which in Figure 10 implement the objective relay optics 302 of Figure 9. The beam also passes through beam splitting optics 300.

[0260] The beam continues to collimating optics 204, optionally implemented as a moveable lens to allow use of the Scheiner principle discussed in relation to Figure 11. The focus length of collimating optics 204 approximately matches the distance to folding mirror 404. More generally, the focus length approximately matches the distance to the focus point of objective relay 302. This allows beams that were reflected at different angles from scanning unit 106 to return to propagating parallel to each other, although positioned differently in space.

[0261] The beam continues next through optics-to-eye 206, illustrated comprising beam splitter 406 and beam combiner 408. The beam enters the subject’s eye 108 through cornea 410 and pupil 412. Some light reaching retina 110 is reflected back from the retina 110 to the pupil 412 and the cornea 410.

[0262] The reflected beam continues passing through beam combiner 408 and reaches beam splitter 406. Beam splitter 406 reflects the light to the objective test detection unit 102, illustrated as comprising lens 414 and detector 416. The reflected light from the retina 110 reaching the objective test detection unit 102 contains refractive information from the subject’s eye 108, which may be analyzed according to the Scheiner principle, e.g., as next explained. Reference is now made to Figure 11, which is a schematic optical diagram of the Scheiner principle, performed, for example, using the optical arrangements of Figure 10, according to some embodiments of the present disclosure.

[0263] Three pairs of laser beams 415-417 are shown entering the subject’s eye 108 from the left. The beams in each pair are parallel to each other, but each pair of beams enters the subject’s eye 108 at a (slightly) different angle. In operation, each pair represents a different position of, e.g., lens 204 as it moves to change the vergence of the beams. There are optionally also a plurality of positions (for example, at least three) at which beams enter the eye (e.g., at different meridians of the eye), and those beams may be presented simultaneously with each other.

[0264] Near the retina, the location of the crossing of each beam pair depends on the incident angle of the beam pairs, as modified by the magnifying power of the anterior segment of the eye (e.g., lens and cornea) to pass through pupil 412.

[0265] By controlling beam source 102 and scan unit 106 in correlation with adjustments to collimating optics 204, it is possible to control both the incident angle of the beam pairs and their location when impinging on the subject’s eye 108. Suitable adjustment results in each pair’s crossing exactly on the retina 110. This state is detected by imaging the retina onto the detector 416, which can be coordinated to move together with lens 414 when another lens is between lens 414 and the eye; or lens 414 can move relative to detector 416 to compensate for the refractive error of the subject’s eye 108. The position of collimating optics 204 and scan unit 106 when the subject’s eye 108 is focally illuminated by beam source 102 corresponds to a certain refractive error in the specific locations of the subject’s eye 108 on which the beam impinged. With suitable selection of a plurality of locations on the anterior segment of the subject’s eye 108 to receive beams, values of spherical cylindrical and axis of the subject’s eye 108 can be derived.

[0266] During the objective measurement, the subject is encouraged to focus into the distance, maintaining a relatively weak accommodation. The subject is instructed, for example, to attend to a target (e.g., a blurred image) which is experienced as perceptually distant encouraging them to accommodate lenses of their eye(s) accordingly. In some embodiments, the target is created by a retinal scanning display system used also as the subjective testing optical subsystem for subjective visual acuity examination.

[0267] Reference is now made to Figure 12, which is a schematic optical diagram of a subjective testing optical subsystem, according to some embodiments of the present disclosure. In some embodiments, the arrangement of Figure 12 corresponds to the elements of blocks 952 and 956 of Figure 9. Beam source 210 emits one or more beams that go through combining and collimating optics 212 and cylindrical correction unit 214; placed, for example, in the corresponding gray area. Optionally, cylindrical correction unit 214 (corresponding in construction to cylindrical correction unit 214) is placed elsewhere in the optical path, for example, just before or just after spherical correction unit 218. In some embodiments, this corresponds to any of the cylindrical and axis correction arrangements described in relation to Figures 1A-2B.

[0268] In some embodiments, the one or more beams are reflected from scanning unit 106 through relay lens 400 to beam splitter 300. These elements are optionally used in common with the objective testing optical subsystem, e.g., of Figure 10. At beam splitting optics 300, objective and subjective illumination beams are split (e.g., the subjective illumination is reflected, while in Figure 10, the objective illumination passes through).

[0269] The one or more beams pass through the spherical correction unit 218 (placed, for example, in the corresponding gray area), and through another relay lens 500.

[0270] As shown, subjective relay optics 216 comprises relay lenses 400 and 500 which relay the one or more beams onto the subject’s pupil 412.

[0271] After relay lens 500, the one or more beams are directed to the subject’s eye 108 by optics- to-eye 206. As shown, optics-to-eye 206 comprise folding mirror 502 and beam combiner 408 (shown also in Figure 10). The one or more beams continue passing through the cornea 410 and pupil 412 to reach the retina 110 where they create an image.

[0272] Reference is now made to Figure 13, which is a schematic optical diagram of combined objective and subjective testing optical subsystems of an optical system 101, according to some embodiments of the present disclosure. In some embodiments, the arrangement of Figure 13 corresponds to many of elements of Figures 10 and 12, in combination. The objective and subjective illumination beams are shown as having been previously combined together (by further elements not shown) before being reflected by scanning unit 106 at the same angle.

[0273] Beam-combining optical elements include, for example: an element that allows light to pass or be reflected depending on the light’s wavelength; a diffractive optical element such as a diffractive beam combiner; and / or an optical wave guide, for example, on a photonic integrated circuit. Combining of beams may occur before or after being collimated by one or more collimating lenses. Alternatively, the beams impinge on the scanning unit 106 at different angles, and spatial relationships of components further along the remainder of the optical path are suitably adjusted for the difference. As shown, the reflected beams from scanning unit 106 for the objective and subjective measurements reach lens 400 and are separated by beam splitting optics 300. The beams for the objective measurements pass through objective relay optics 302, comprising lens 402 and lens 400. The beam is then reflected by folding mirror 404 through collimating optics 204, passes beam splitter 406, and passes beam combiner 408. Beam combiner 408 directs the beams used for objective and subjective measurements to the subject’s eye 108. Reflection from the subject’s eye 108 passes through beam combiner 408 and is reflected by beam splitter 406 into detection unit 102, where the reflection light is analyzed.

[0274] Along the subjective illumination optical path, relay lens 400 serves as the proximal relay lens of subjective relay optics 216. Beam(s) are separated from the objective illumination beam at beam splitting optics 300 (e.g., reflected). The beam(s) pass through spherical correction unit 218 (placed, for example, in the corresponding gray area) to reach the distal relay lens 500 of subjective relay optics 216, from which the beam(s) are relayed onto the subject’s pupil 412. Relay to eye 108 is via optics-to-eye 206, illustrated as comprising folding mirror 502 and beam combiner 408. The beam(s) enter the subject’s eye 108 and reach the retina 110 where they create an image.

[0275] Optionally, optical system 101 of Figures 9-10 and 12-13 includes akeratometry unit 112. Keratometry unit 112 is configured to measure corneal shape of the subject’s eye(s). This allows acquiring further and / or confirming information regarding optical functioning of the subject’s eye 108; for example: regarding astigmatism, astigmatism axis and / or total corneal power, and / or the cornea’s radius of curvature.

[0276] Dual-Scanning Unit Arrangement

[0277] Reference is now made to Figure 14, which is a schematic optical diagram of combined objective and subjective testing optical subsystems of an optical system 101 using two scanning units 702, 708, according to some embodiments of the present disclosure. Each of the scanning units 702, 708, scans in one dimension. They are arranged so that together they can perform a two- dimensional scan.

[0278] Combined beams 700 of the objective and subjective optical subsystems impinge on the first scanning unit 702 and are relayed via lenses 704, 706 to a second scanning unit 708. Combining of the beams is not shown. The beams continue to lens 400 and from there to the subject’s eye 108 through arrangements of elements which are, for example, corresponding to arrangements of Figures 9-10 and / or 12-13. The relay between the two scanning units 702 and 708 indicated by two lenses, is optionally implemented by any suitable number of lenses. Optionally, there are no relay components positioned between scanning units 702 and 708.

[0279] Objective Optical Testing with Ray Tracing Aberrometry

[0280] Reference is now made to Figure 15, which is a schematic optical diagram of combined objective and subjective testing optical subsystems of an optical system 101, with the objective testing optical subsystem using ray tracing aberrometry, according to some embodiments of the present disclosure. The objective and subjective illumination beams are shown as having been previously combined together (by further elements not shown) before being reflected by scanning unit 106 at chose angles for each exam.

[0281] Regarding beam(s) used in objective testing measurements, combined beams 700 impinge on scanning unit 106, and may be internally diverging, converging, or collimated as they do so. For example, they may be focused or approximately focused when impinging on scanning unit 106.

[0282] Beam-combining optical elements include, for example: an element that allows light to pass or be reflected depending on the light’s wavelength; a diffractive optical element such as a diffractive beam combiner; and / or an optical wave guide, for example, on a photonic integrated circuit. Combining of beams may occur before or after being collimated by one or more collimating lenses.

[0283] Scanning unit 106 reflects the beams to beam splitting optics 300, which separate the objective test illumination beam(s) from those of the subjective and / or objective focus target illumination pathway.

[0284] Beam(s) for objective measurements pass objective relay optics 302 (Figure 9); as shown in Figure 15 comprising lens 402 and lens 400. In some embodiments, the beams reflect from folding mirror 404. Collimating optics 204, illustrated as a stationary lens, optionally comprises one or more stationary, moveable, and / or tunable lenses.

[0285] Beams reflected at different angles from the scanning unit 106 propagate parallel to each other while collimated, though positioned differently in space. The beams continue through beam splitter 406 and beam combiner 408 and enter the subject’s eye 108, passing through the cornea 410 and pupil 412. The beams reach the retina 110 and are reflected back from the retina 110 to the pupil 412 and the cornea 410. The reflected light continues passing through beam combiner 408 and is reflected by beam splitter 406 to the lens 800 and onto a detector 802. Beam splitter 406, beam combiner 408, lens 800 and detector 802 are optionally fixed relative to each other; but moveable together and / or provided together with another lens before them that is moveable to compensate for refractive error. Detector 802 is implemented, for example, using a photo-sensor, a quad photo-detector, a CCD camera, a positioning sensitive detector (PSD), and / or another photosensor.

[0286] The reflected light from the retina 110 reaching detector 802 contains refractive information from the subject’s eye 108. Different beams resulting from different angles of scanning unit 106 are illustrated. All the beams are parallel to each other upon reaching the subject’s eye 108, but enter the subject’s eye 108 at different locations. By controlling beam source 200 (contributing to combined beam 700) and scan unit 106 it is possible to sequentially change the location at which the beam impinges on the subject’s eye 108. The detector 802 measures the exact location where each beam reaches the retina 110 by means of the retro -reflected light. This process continues until several separated points are projected into the entrance pupil 412. This way a correlation is obtained between the direction that the light beams have taken while entering and leaving, allowing a reconstruction of the real wave-front error. From such data, values of spherical, cylindrical, axis and corneal curvature of the subject’s eye 108 can be derived. The subjective visual acuity exam subsystem is optionally configured, for example, as described in relation to embodiments of Figures 12-14.

[0287] Dual-Scanning Unit Arrangement

[0288] In some embodiments, the general arrangements of Figure 15 are modified by combination with the dual-scanning unit arrangement described in relation to Figure 14. Again, each of scanning unit scans in one dimension; together they can perform a two-dimensional scan.

[0289] Testing of Visual Acuity and / or Refractive Error

[0290] For use in subjective visual acuity testing, the image formed by the scanned beam on the retina 110 comprises, for example, a visual acuity exam chart such as a Snellen chart, Landolt ring chart, tumbling E chart, Lea test, HOTV chart, clock dial chart, sunburst chart, spatial frequency chart (e.g. , EIA Resolution Chart 1956, ISO 12233, USAF 1951) and / or any other image or images for evaluating the subject’s refractive error. Optionally, 3-D and / or binocular presentation capabilities used to present visual test images as apparently three dimensional and / or localized in depth. For example, depth cues may be used to modify the apparent size / distance of stimuli, optionally while retaining the same angular size. This may assist in controlling accommodation, for example. Optionally, stimuli associated with different depths (that is, different depth cues) are presented simultaneously, resulting in a three dimensional appearance of the test image.

[0291] As a starting point for the subjective exam, different information can be used for shaping the beam forming in the initial images. For example, the subject’s last prescription, or the subject’s glasses can be measured or the values obtained previously in the objective visual acuity exam is used. Initial values for spherical, cylindrical and / or axis are used to shape the scanned laser beam which produces the image. Values used for the starting point can be used as initially obtained or with an added or subtracted factor (e.g.. a calibration factor, which may be determined empirically).

[0292] Based on input from the subject, the spherical, cylindrical and axis are adjusted, to seek parameters producing an image on the subject’s retina 110. reported by the subject as optimal.

[0293] The changes to the beam’ s shape (divergence / convergence, astigmatism and astigmatism axis, corresponding to spherical power, cylindrical power, and cylindrical axis) to produce the optimized image on the subject’s retina 110, are used to derive the subject’s subjective values for spherical, cylindrical and axis refractive errors. Following the subjective visual acuity exam, a complete eyeglass prescription can be produced.

[0294] Reference is now made to Figure 16, which is a schematic flowchart of a method for measuring the refractive error of subject’s eyes and providing a prescription for eyeglasses or contact lenses, according to some embodiments of the present disclosure. The examiner, the subject themself, or a designated person performs and / or supervises the operations of each block, optionally remotely. In some embodiments a computer processor is used to operate aspects of device function, e.g., in response to sensed information, in response to remotely and / or locally input commands, and / or following one or more internally defined protocols.

[0295] At block 900, in some embodiments, the subject is optionally asked to fill in (or otherwise provide) personal information and relevant known medical eye history. At block 902, in some embodiments, the subject’s eye is aligned correctly to the apparatus; for example, as detailed in relation to FIG. 17.

[0296] Brief reference is now made to Figure 17, which is a schematic flowchart of a method to align a subject’s eye to an optical system 101, according to some embodiments of the present disclosure.

[0297] At block 1000, in some embodiments, the subject inserts their head onto a mount. This comprises, in some embodiments, a chin rest, forehead rest, and / or cheek bone rest; and / or another mechanical arrangement to keep the subject steady in a certain place. At block 1002, in some embodiments, a rough alignment process is performed, continuing, for example, until cameras located in the apparatus are able to recognize and position the subject’s pupils relative to the apparatus. This process can be performed manually (e.g. , position adjustments are performed by hand) and / or automatically under control of the processor (e.g., adjustments are performed using actuators, under feedback control from a controller which is monitoring camera images or other sensor data monitoring mono-ocular and / or binocular eye alignment (e.g., pupil alignment) inside and / or outside the apparatus.

[0298] At block 1004, in some embodiments, e.g., after sensing recognizes the subject’s pupil position, a fine alignment process is initiated (e.g., with further motor actuations, optionally under image or other sensor feedback-based control by the processor). This results in the pupil being in the correct position relative to the optical axis of the apparatus on, e.g., up to six axes (x, y, z, roll, pitch, and yaw). Optionally pitch and / or yaw adjustment is omitted. Optionally roll is omitted. Optionally one one or two of the displacement axis is omitted or controlled manually.

[0299] At block 1006, in some embodiments, an optional confirmation of positioning is provided via images with marked boundaries being projected to the eye, with input from the subject indicating angles at which the projected beams enter the subject’s pupil 412. These can be used to define the subject’s field of view (FOV). Optionally, the FOV is determined automatically (e.g., by imaging of the retina). Optionally, the fine alignment process of block 1004 is relied on to ensure an appropriate FOV, or the FOV is otherwise assumed to be suitably arranged as a result of other arrangements.

[0300] From block 1008, in some embodiments, the eye exam proceeds, optionally for both eyes together, or the eyes in alternation.

[0301] Now with returning reference to Figure 16, a first exam is initiated on the corrected positioned subject.

[0302] At block 904, in some embodiments, the subject’s accommodation is optionally analyzed. The analysis may be based on initial attempts at objective testing, eye tracking, or another form of electronic sensing. The result potentially assists (e.g., is used by the processor) in determining device settings which can compensate for incomplete accommodation, such as the variation of spherical correction to the focus image. Optionally, extra measures are taken to promote accommodation, such as presentation of objects in a passthrough-visualized scene beyond the testing optics themselves, an image sequence presented (e.g., via the subjective illumination optical pathway) to draw the subject’s attention, or another method. Initiation of such measures is optionally suggested by outputs of the processor to a user interface, and / or performed by the processor.

[0303] At block 906, in some embodiments, an objective refractive error exam is performed. Optionally operations of blocks 904 and 906 are performed together, e.g., iteratively as test results are obtained. The test is performed with the subject looking at a target (usually a blurred image, or an image including both blurred and sharply-presented elements), optionally created by the optical path used also (e.g., used later on and / or simultaneously) to perform a subjective visual acuity exam. In some embodiments, the objective refractive error exam is performed on both eyes simultaneously. In some embodiments, the testing device includes a moving element which actuates to adjust a relative angle between projection systems showing images to either eye during acuity testing. This adjustment may be used to change the apparent distance of a binocularly presented target. As the subject adjusts, there may be changes to eye vergence and lens accommodation, e.g., lens accommodation may be drawn to a distant focus. Due to the accompanying change in eye vergence, the angle of the subject’s eye may also change. In some embodiments, adjusting the relative angle between projection systems also adjusts the angle of the optical path which projects objective testing light patterns onto the retina, thereby maintaining it in angular alignment with the eye. Adjustments are optionally performed under control of the processor as it follows a protocol, and / or upon sensed detection of the position and / or sensed state (e.g., pupil size, fixation stability, and / or accommodation) of the eyes of the subject.

[0304] In some embodiments, objective testing (e.g., infrared illumination-based objective testing) is performed at least partially simultaneously with other testing, e.g., the subjective testing measurements of blocks 910-912. Through simultaneous testing, there is potentially a savings of time, and / or an opportunity to enhance objective testing results, e.g., as a subject focuses to different distances during subjective testing. This may occur, for example, as a result of a clearer presentation of targets as the optical corrections used in subjective testing change. In some embodiments, the subjective test image itself is used as a target for the objective test; e.g., presented in depth (and optionally “swept” in depth, e.g., moved from apparent foreground to apparent distance during transitions in the testing) to help set an appropriate accommodation for ongoing objective testing. Such modulations of the subjective test image are optionally performed by the processor as part of a predetermined protocol, and / or in response to sensed state of the eyes of the subject.

[0305] At block 908, in some embodiments, a keratometry measurement is optionally performed, according to whether optics configured to perform this test are present (e.g. , as described in relation to Figures 6 and 7, but optionally provided together within any of the optical system 101 embodiments described herein).

[0306] Beginning with block 910, in some embodiments, subjective measurements are optionally conducted, comprising one or both of a far visual acuity exam at block 910 (including examination for astigmatism), and a near visual acuity exam at block 912.

[0307] In some embodiments, tests make use of a binocular test target presentation capability to assist testing. In some embodiments, the subjective test comprises a switching of at least a portion of the presented target between two eyes, and / or presentation of different parts of the target to different eyes. The subject may be asked (optionally, prompted by the device itself) to evaluate, in effect, which eye sees the target more clearly, e.g., by being asked when they see the target most clearly, or what part of the target they see most clearly. In some embodiments, the response is provided directly to and / or measured by the device itself. In some embodiments, the processor follows a protocol, based on the inputs received, to determine how the optics of the device should be altered, e.g., to correct for spherical and / or cylindrical aberrations of the subject’s eye(s). In some embodiments, targets presented to each eye are made sufficiently distinct (e.g., stripes of different orientations) that their separate adjustments can (potentially) be distinctly perceived and reported.

[0308] In some embodiments, testing optical power (cylinder and / or spherical) oscillates through a range with relative rapidity (e.g., slightly more quickly than the subject can respond before conditions have changed), and the subject is instructed to signal when they see a certain condition of clarity and / or matching. While there is potentially a lag in subject response, the oscillation may approach the signaled condition from opposite sides, so that the lag phase can be estimated (e.g., by the processor, for example by averaging response phases) to help determine the moment of the perceptual condition being signaled. This potentially helps to speed up the test process, and / or allows a larger and / or more heavily sampled number of optical correction conditions to be evaluated. Optionally, the rate of oscillation is adjusted to the response performance of the subject as appropriate, e.g., to maintain suitably consistent responses. Performed more slowly, the oscillation potentially helps determine if there is accommodation hysteresis (e.g., differences in eye accommodation depending on whether optical correction power is increasing or decreasing). Adaptation to patient performance is optionally performed automatically by the processor, based on patient performance characteristics such as consistency and / or hesitancy of responses received.

[0309] Perceptual simultaneity is not necessarily used. For example, cylinder power may be evaluated by movement of a cylinder lens arrangement at a relatively slow oscillation rate, e.g., 1 Hz or lower. A displayed pattern may be shown to the subject which advances (optionally smoothly) down, across, around, or in another manner through the display area. The subject may be instructed to look for (and optionally at) the region of greatest clarity. They may report it (e.g., name a number or other label positioned nearest that region, or otherwise describe it), and / or the eye position itself is optionally used as an indication of where optical clarity is perceived to be best.

[0310] In some embodiments, eye movements (e.g. , as measured by an eye tracking detector inside the device) themselves lead the stimulus presentation and configuration of the optics. For example, cylinder power, cylinder axis, and / or spherical power may be mapped through positions on the display. As the subject looks over the display region, the optics are adjusted to match the mapping. The region where the subject’s gaze is drawn and / or settles is, accordingly, selected as a basis for a further round of testing and selection, e.g., optionally after re-mapping. Re-mapping may be continuous, e.g., such that as the eye moves in a particular direction seeking a region where the target takes on greater focus, the mapping “scrolls” (perhaps more gradually) so that the eye is drawn back toward the center of the display area. Optionally, the optical task is varied during a test to reduce subject fatigue, e.g., switching between different ways of dividing the display area among optical settings, different target shapes and / or colors, and / or different patterns of target movement.

[0311] In some embodiments, intensity variations in the subjective testing illumination are used to help evaluate subject visual field capabilities, at least in some portion of the subject’s visual field, e.g., near the fovea. For example, the subject may be asked to evaluate (and signal) when two illumination areas are matching and / or visibly distinct in intensity, when and / or where they can perceive a change in illumination intensity, when and / or where they can perceive an illumination gradient, or when / where another criterion is met.

[0312] In some embodiments, a subject is given at least partial control over the visual stimulus and / or optical correcting power, allowing them to manually select for themselves conditions at which a certain subjective perception criterion is met. Optionally, the selection is repeated from different initial conditions, and / or from among different available ranges. For example, the subject may rotate a knob (or control another selector) to select an orientation of cylindrical correction which leads to the greatest distortion and / or minimal distortion (e.g., clearest separation of two nearby lines or spots), and / or to select a power of cylindrical and / or spherical correction which leads to the least distortion, to distortion which matches among their two eyes, or according to another criterion. At block 914, in some embodiments, a prescription for refractive glasses and / or contact lenses is optionally prescribed.

[0313] Reference is now made to Figure 18, which schematically illustrates a compact visual acuity and / or refractive error testing system 1701, according to some embodiments of the present disclosure. Further reference is made to Figures 19A-19B, which schematically represent table- top use of compact visual acuity testing kit 1701 to perform visual acuity testing on a subject, according to some embodiments of the present disclosure.

[0314] In some embodiments, (for example, as shown in Figure 18), visual acuity and / or refractive error examination system 1701 comprises controller 1100, optometry apparatus 1102, and mechanical head positioning unit 1104. Optometry apparatus 1102 is shown as approximately head-width, with a somewhat smaller depth and height, but it may optionally be of any size appropriate to containing the testing optics, e.g., with a maximum dimension of 20-50 cm. The testing optics are optionally binocular, or optionally monocular.

[0315] Optionally, mechanical connector unit 1106 is provided, configured to support optometry apparatus 1102 above a surface such as a tabletop. Optionally mechanical connector unit 1106 is standalone (e.g., as shown in Figure 19A). Optionally, it mounts to mechanical head positioning unit 1104, for example, as shown in Figure 19B.

[0316] The schematic view of Figure 18 illustrates visual acuity and / or refractive error examination system 1701 stored by and / or transferable as a hand-carried unit; e.g., enclosed by a latching case 1116 with base 1116B, lid 1116C, and handle 1116A. Case 1116 may provide internal supports (e.g., foam and / or straps) to hold system elements securely in position (not shown).

[0317] Optometry apparatus 1102 comprises a visual acuity and / or refractive error measuring device constructed, for example, according to principles and design elements described in relation to any of the other embodiments described herein; e.g., Figures 7-15, optionally operable according any of the methods of Figures 16-17, and optionally including features (e.g., cylindrical correction features) as described in relation to any of Figures 1A-6.

[0318] In some embodiments, controller 1100 comprises input controls 1100A (Figure 19A) for the examiner 1108 to operate the system, and a display section 1100B upon which the examiner 1108 can observe images, data, procedures, and any other information for conducting visual acuity exams. Optionally, examiner 1108 is present via telecommunications connection, e.g., at an offsite location. Optionally a technician assists positioning the subject, and the examiner 1108 performs the test itself. Arrangements for examiner (test supervisor), and technician (assistant) may correspond, for example, to those described in relation to Figures 5A-5B and / or 16. Optionally, functions for input control and display are combined, e.g., as a touchscreen- equipped controller 1100 (Figures 18 and 19B).

[0319] To perform visual acuity examinations, optometry apparatus 1102 is aligned with the mechanical head positioning unit 1104. Mechanical head positioning unit 1104 serves to keep the subject’s head 1110 in a certain position. It comprises, for example, chin rest 1104B (optionally adjustable in height), forehead strap 1104C, and / or another element which contacts the subject’s head to assist in maintaining its position. In particular, head positioning unit 1104 helps to keep the eyes 108 of subject’s head 1110 at a certain location during the exams.

[0320] In some embodiments, optional mechanical connector unit 1106 supports optometry apparatus 1102 in an appropriate position relative to head positioning unit 1104. It may be freestanding, connected to head positioning unit 1104 (e.g., via clamp 1104A) or otherwise configured to connect or stabilize the apparatus; e.g., to a table 1109 or another surface. Optionally, spatial adjustments (e.g., X, Y, and / or Z displacement) are provided to adjust the position of subject 1110 in head positioning unit 1104, the position of optometry apparatus 1102 as held by mechanical connector unit 1106, and / or clamping position relative to table 1109.

[0321] Brief reference is now made to Figure 19C, which schematically illustrates a refractive error examination system 1701 installed in a kiosk stand 1901. In some embodiments, the apparatus is operated as a service provided as part of a kiosk engaged in selling eyewear and / or optometric services; for example, a space in a shopping mall or other location of commercial (e.g., consumer retail) activity.

[0322] For example, in some embodiments, the kiosk is located in a portion of an open retail space, e.g., at least two meters from any wall, open to bypasser foot traffic on two or more sides, and / or disconnected from any wall.

[0323] In some embodiments, the kiosk comprises one or more display cabinets. In some embodiments, the kiosk comprises a countertop. Optionally, examination system 1701 is accessible to subjects at the countertop. Optionally, examination system 1701 is accessible to subjects in a space bounded by the countertop, the one or more display cabinets, or any combination thereof.

[0324] In some embodiments, subjects place orders for corrective optics, based on a lens prescription obtained through operation of examination system 1701, the order including one or more articles directly displayed and / or exemplified by display in the kiosk (e.g. a glasses frame or portion thereof, a case, or a care accessory). Reference is now made to Figures 20A-20C, which schematically illustrate head-worn implementations of a vision testing system, according to some embodiments of the present disclosure. Figures 20A-20B show head-worn embodiments, with optics of the testing system enclosed in housing secured with a strap to the head. Figure 20C illustrates a more compact embodiment as glasses or goggles. In either case, the optics are optically provided together with other suitable elements of a kit, for example, carrying case 1116, controller 1100, and / or cabling 1103.

[0325] Use of Optical Distortion in Visual Acuity Testing

[0326] Reference is now made to Figures 21A-21E, which illustrate examples of optotypes based on a 5x5 grid, according to some embodiments of the present disclosure. Examples of abstract and / or letter-shaped optotypes 2101A-2101E are shown in Figures 21A-21E, respectively.

[0327] Use of a 5x5 grid as the basis of an optotype is found, e.g., in the example of Snellen charts, for which the strokes of letter symbols are laid out using blocks of such a grid, scaled appropriately for presentation at a size suitable to evaluate what a test subject can distinguish. The subject may be asked to identify the orientation of an optotype presentation, and / or asked to distinguish the presented optotype from among a plurality of different optotype shapes. For example, the subject may be prompted to choose the presented optotype out of a list of optotypes presented at a larger size, and / or prompted to “match” optotypes of the same size to each other by shape and / or orientation; e.g., by indicating eye movements, operation of a hand-controlled cursor, verbal indications, or another method.

[0328] In some optotypes, a single feature (a single “square”) provides a visual indication of optotype orientation, e.g., the small gap 2102 of optotype 2101A.

[0329] In the case of optotype 2101B, multiple features, extending over longer distances, combine to provide indications of orientation, z.e., the horizontal limbs 2103 (and their intervening gaps 2104). These differences in the “intensity” of optotype directionality cues potentially makes identification of the orientation of optotype 2101B slightly easier near the acuity threshold of a subject than the orientation of optotype 2101A.

[0330] Furthermore, in both of these cases (in the orientations shown), it is scaling along the vertical direction which primarily affects the size of the salient (identifying) features for optotype orientation, while horizontal scaling is almost irrelevant to identification of optotype orientation. The cases of Figures 21 C-2 IE show various examples of intermediately emphasized directionality cues. Potentially, the contribution of axis scaling to the identification of optotype orientation is less strongly differentiated in these more visually complex examples.

[0331] Reference is now made to Figures 22A-22B, which illustrate examples of optotypes at different rotations, according to some embodiments of the present disclosure. Optotype 2101A is shown in Figure 22 A, and optotype 2101B is shown in Figure 22B.

[0332] Here, the visual presentations of the optotypes are drawn smoothly (e.g., as if with high pixel resolution), and without scaling effects due to optotype orientation. However, at small sizes, the various oblique presentation angles are optionally regarded as different optotypes to the rectified orientation presentations, despite being closely related in shape. This is because of how the shapes are influenced by the underlying pixel grid.

[0333] Reference is now made to Figure 23, which illustrates a square-pixel rendering of optotype 2101B on a 10x10 grid with 2-pixel wide strokes (and gaps between them), according to some embodiments of the present disclosure. Further reference is made to Figure 24, which illustrates a square-pixel rendering of optotype 2301B on a 15x15 grid with approximately 2-pixel wide strokes (and gaps between them), according to some embodiments of the present disclosure. Reference is also made to Figures 25A-25B, which show optotypes 2101B and 2301B in a same corresponding orientation, allowing comparison of their dimensions, according to some embodiments of the present disclosure.

[0334] At the expanded scale shown, and rendered at a 45° angle to closely resemble the “rectified” optotype 2101B, the edges of optotype 2301B shown in Figure 24 are jagged, although “on average”, the stroke width is close to the 2-pixel stroke width shown for optotype 2101B in Figure 23. The example of 45° orientation is of particular interest, as it can be represented (even though “jaggedly”) with pixel-level uniformity at small scales, but it is optionally not the only subangle of 90° which is used. At least for pixels with a square aspect ratio, the 45° angle may be judged to exist, for example, when there is a strictly diagonal (e.g., corner contacting only) arrangement of three, four or more pixels with the same intensity, in adjacent side-contact with a similar diagonal arrangement having a contrasting intensity. In some embodiments of the present disclosure, for example, linear features extending through 30° and 60° angles may be represented with lines having slopes of 1 / 2 or 2, respectively (e.g., at least four pixels occur in two or more pairs of side-adjacent pixels, the pairs being adjacent to each other only across comers, and also in adjacent-side contact with a similar arrangement of pixels having a contrasting intensity). At sufficiently small scales (e.g., as the overall extent of the optotypes approaches the visual acuity threshold of a subject), the difference in outline shape may become consciously imperceptible. However, their differences nevertheless potentially place the acuity thresholds of these optotypes (e.g., the sizes at which they can be reliably distinguished as to their orientation and / or identity) at different levels. For a given presentation system, thresholds can be determined, e.g., by comparison of results across multiple subjects, allowing them to be calibrated appropriately.

[0335] As noted in Figures 25A-25B, the “jagged” presentation of optotype 2301B is also slightly larger on average, (about 7% than optotype 2101B, as shown) due to the mismatch in the diagonal extent of a pixel compared to its horizontal or vertical extent. It is noted that optotype 2301B generally cannot actually be presented in the rectified orientation shown, due to limitations imposed by the underlying pixel grid. The difference in size is not necessarily significant to results in itself, but may be noted as a contributing factor to differences shown in following figures.

[0336] It should also be noted that potentially the “jagged” edges of the presentation of optotype 2301B may alter the threshold sensitivity of visual acuity to its salient features, e.g., they may lower sensitivity, offsetting in whole or in part the effect of a slightly larger presentation size.

[0337] Reference is now made to Figures 26A-26E, which illustrate different anisotropic optical scaling transformations of optotype 2101B, according to some embodiments of the present disclosure.

[0338] Figure 26A simply shows optotype 2101B as shown in Figure 23, with the addition of a relative scale indication 2601A (indicating 100% of baseline height), and a “blank” cylindrical lens indication 2603, showing that there is no net anisotropy in the subject-apparent magnification at which optotype 2101B is presented. A two-pixel stroke width presentation is used as an example here, but it should be understood that other integer number stroke widths (e.g., 1, 3, 4, 5, or more pixels) are optionally used. The two-pixel stroke width instance is potentially of particular interest when angular pixel size is about 0.5 arc seconds, since this places a 10x10 pixel presentation of optotype 2101B near the standard threshold used to indicate “normal” visual acuity. Reducing apparent pixel size enough to allow a three-pixel stroke width at this size may substantially reduce the available size of the visual field (i.e., by about a third), which represents a potentially undesirable compromise in terms of maximum presentation size, visual display cost / complexity, or another aspect of device design.

[0339] Figure 26B represents a case where optical scaling of about 25% has been imposed on the presentation of optotype 2101B, so that it assumes height-elongated shape 2600B. Figure 26C represents a case where an orthogonally oriented optical scaling of about 25% has been imposed on the presentation of optotype 2101B, so that it assumes width-elongated shape 2600C.

[0340] Such anisotropic magnification may occur, for example, due to effects of cylinder power anisotropy; e.g., as indicated by schematic lenses 2602, 2603 where darker parts of the lens are, e.g., thicker. The scaling is not necessarily due to the effect of cylinder power, but this particular case is of interest, e.g., in relation to the embodiments of Figures 1A-1B (and those of the other figures which reference one or both of these embodiments, e.g., Figures 3A-15). Embodiments allowing cylinder power adjustment using the lens configuration of Figure 1A may introduce suitable levels of anisotropic magnification, when used in a pattern of negative / positive / negative diopter cylindrical lenses, the negative diopter lenses corresponding to lenses 8A-8B of Figure 2, and the positive diopter lens corresponding to lens 6 of Figure 1A. However, this example is not limiting. For example, a positive / negative / positive diopter arrangement has also been found to produce useful results; i.e., the first and third lenses are arithmetically signed the same, and the middle lens is signed oppositely to them.

[0341] Other reasons for anisotropic scaling include the intrinsic structure of the display itself (e.g., rectangular pixels instead of square), baseline anisotropies introduced by the optical pathway conducting display illumination to the retina, and anisotropies introduced during adjustment of the optics for reasons other than adjustment of cylinder refraction; e.g., changes in optical element alignment.

[0342] The 25% scaling used in these examples is also an example. The amount of scaling anisotropy present may range, for example, from about 0% to about 50% (e.g., about halfway between sizes that can be achieved by insertion of an additional pixel to stroke width). In some embodiments, scaling anisotropy ranges from about 7% to about 20%. The value achieved depends on the overall design. Typically, it also depends on the amount of cylinder power which is added into the system during a particular phase of testing. It may be a larger value for subjects who need a larger cylinder correction to compensate for the refractive error of their eye.

[0343] In the case of Figure 26B, the 25% increase in height potentially also makes the optotype presentation more easily recognizable, since it increases the size of the highly salient group of features comprising the alternating limbs and gaps of optotype 2101B. If recognition of the unsealed optotype is considered as indicative of 6 / 6 vision, then, this scaled optotype now optionally is considered as providing an indication of 6 / 7.5 vision. To get to the next stop of 6 / 9 vision, three pixel limb widths could be used instead, allowing the optotype presentation to be 50% larger. It is noted that it should make relatively little difference to at least some visual distinctions requested of a test subject when the optotype 2101B is stretched horizontally as shown in Figure 26C, since the spacing of the most extensive features allowing the orientation to be determined (the horizontal limbs) is unchanged in this case ( / '.<?., length 2601C and length 2601A are identical). However, the thickening of the vertical stroke may nevertheless convey some additional visual information contributing to its salience. In any case, the effective visual threshold of the anisotropically modified optotype presentation 2600C can be determined for its overall shape, so that relative contributions of horizontal vs. vertical magnification need not be separately identified.

[0344] Oblique relative orientations of optotype presentation compared to magnification anisotropy are also possible, in some embodiments of the present disclosure. For example, in Figure 26D, magnification scaling (again an increase of about 25%) is applied along an axis extending from lower right to upper left, as indicated by schematic lens 2602 and the arrow alongside it. This largely results in a height increase, but somewhat lessened (e.g., line 2601D is longer by about 19%) due to the obliquity. In Figure 26E, a direction of magnification orthogonal to that of Figure 26D is used, with a correspondingly lower effect on length 2601E (about a 6% size increase). Again, actual movement of the recognition threshold of these optotype presentations may be different than is explained by the height change alone, e.g., due to concomitant changes in orthogonal size, and / or due to distortion of the shape whose orientation should be recognized.

[0345] When subjects are asked to recognize such distorted shapes, optionally the reference shapes are also shown distorted to the subject, so as to facilitate understanding. It is noted that the optical distortions of Figures 26D-26E have the effect of distorting the shape of the pixel grid itself, so that the “smooth edges” of the optotype presentations are potentially maintained. However, it may be appropriate to adjust the images used to generate example optotype presentations used for comparison, so that they more closely approximate what the test subject is seeing. For example, optical anisotropies in magnification may not be uniform throughout the visual field.

[0346] Conversely, images used as optotype presentations can be adjusted by changing their pixel structure layout appropriately. For example, in the case of Figure 26D, there is a vertical shift of approximately one pixel upward moving from right to left. Introducing a vertical pixel shift for about half the image at the level of the illuminating display element (potentially with anti-aliasing as well) could in part restore the rectified shape of the optotype (“rectified”, as used for shapes described herein means “square or rectangular”). This is not necessarily without effect on test results, however; e.g., “blurring” due to anti-aliasing may impact on the acuity threshold which must be reached in order to correctly identify the optotype.

[0347] While the intermediate values do not necessarily reach all the way to a threshold corresponding to a standard visual acuity value (e.g., not quite to detecting the 6 / 7.5 threshold), they may nevertheless serve as values closer to such a value, which may be used to interpolate test results toward or away from it.

[0348] Reference is now made to Figure 29, which schematically illustrates positioning of optotype presentations at different locations in a visual field, according to some embodiments of the present disclosure.

[0349] In some embodiments visual field 2900 contains regions of varying scaling anisotropy. The pattern of said regions itself potentially varies as a function of the optical settings of a testing system, e.g., a current setting of optics which compensate for refractive error of a test subject.

[0350] In some embodiments, the system reaches a condition in which a test which is to be performed should preferably present a stimulus which probes a particular acuity threshold, while at the same time the general optical conditions of the system are set by the history of past optotype presentations to offset the refractive errors of the test subject to the extent these have become known to the system.

[0351] The system may then select, from among the range of varying scaling anisotropies presently available in field of view 2900, a particular location and / or stimulus orientation which will satisfy the test requirements. For example, the region of optotype presentation 2901 may be substantially uniform in all directions. The regions of optotype presentations 2903 and 2903 may be both expanded vertically, so that by rotation the salient features of the optotypes may be more or less emphasized (relatively to the orthogonal direction) by the vertical expansion. Optotype presentations 2904 and 2905 show other types of distortions which may potentially be available.

[0352] Accordingly, and knowing how the system performs under various conditions, the system select how to next present optotypes so that remaining gaps in the testing data (e.g., visual acuity thresholds intermediate to those already tested) may be examined.

[0353] Reference is now made to Figures 27A-27E, which illustrate different anisotropic optical scaling transformations of optotype 2301B, according to some embodiments of the present disclosure. The results may be understood generally as described already for Figures 26A-26E, with the modification that scaling values are adjusted by the relative scaling of optotype 2301B itself relative to optotype 2101B, when placed on a same-sized pixel grid. The examples shown have been rectified in orientation, but it should be understood that as actually presented, the orientation is perceptually oblique, e.g., as shown next to each of the schematic lenses 2603 (blank lens) and 2602 (lens indicating a 25% magnification along the axis of the adjacent double arrow).

[0354] In this case, a height elongation of about 33% is shown for Figure 27 B, while Figure 27 C leaves the 7% height elongation of Figure 27 A unchanged. Height elongation is about 27% overall in Figure 27 D, and about 13% overall in Figure 27 E. Again, height is illustrated as an indication of what may be a primary salient aspect of optotype 2301B, but the effective visual acuity threshold of any of these optotype presentations may be adjusted by a larger or smaller amount, according to determinations which may be made using the device itself.

[0355] It is noted that the perceptual jaggedness of the examples of Figures 27A-27E could potentially be modified by the use of anti-aliasing techniques, e.g., the introduction of “partially darkened” pixels along the borders of the optotype presentations shown. For optotype presentations having smaller pixel counts (e.g., only one or two pixels separating dark features from each other), the effects of anti-aliasing may tend to obscure salient features (e.g., by reducing contrast). Accordingly systems may weigh the significance of anti-aliased optotype presentations differently than non-anti-aliased versions. At larger pixel counts, effects on acuity threshold measurements are potentially less important, since the threshold size being measured is sufficiently large compared to the single-pixel level at which anti-aliasing introduces “features”.

[0356] Reference is now made to Figure 28, which is a schematic flowchart representing a method of subjective visual acuity testing using anisotropically magnified optotype presentations, according to some embodiments of the present disclosure.

[0357] The flowchart is based on a single optotype presentation (e.g., as if presented as one of a sequence). However, it should be understood that many optotypes are presented during a test session, and moreover, that more than one optotype may be presented at a time.

[0358] At block 2802, in some embodiments, optical settings are adjusted to produce spherical and cylinder adjustments as appropriate to the current phase of testing.

[0359] In some embodiments (and typically in at least some of the optotype presentations given to a test subject), the testing methodology used seeks to fully match (by counteracting) the refractive error of the subject. Thus, the cylinder-induced magnification anisotropy (or other magnification difference) introduced is potentially larger for some subjects than for others, as the amount of optical correction introduced to the image presentation pathway is adjusted according to the responses of the test subject. This may be performed, for example, as described in relation to any of the subjective stimulus illumination pathways presented herein, but also is not limited to these examples. Additionally or alternatively (e.g., in a subset of optotype presentations), optical settings are deliberately adjusted to produce a particular anisotropy or other magnification adjustment in test target presentation.

[0360] In particular, it is noted that one visual axis of an optotype’s shape may be more salient to its recognition than the other. In this case, it may be sufficient for recognition of an optotype (at least, in comparison to some alternative presentations of it or another optotype) that just one visual axis be in clear focus. “Clear focus” should be understood relative to the refractive error which the system is trying to match, which is not necessarily what looks focused to the test subject.

[0361] Under these conditions, the optotype may be presentable to the subject using any of potentially several combinations of spherical correction and cylinder correction which add up in their refractive powers to produce the appropriate amount of refractive correction in the axis of greatest salience. The appearance of the optotype presentation along orthogonal axis may, however, be more-or-less blurred.

[0362] Thus, for example, the subject may be instructed to distinguish among two optotypes, e.g., one with a checkerboard pattern and one with a striped pattern oriented with respect to the optics of the system and eye for greatest distinctness of the stripes. The target of the system could be to present the stripes with a refractive correcting power of +2.0 diopters, for example. It could achieve this with spherical power of +2.0 diopters, but also with a spherical power of 0 diopters and a net cylindrical power of +2.0 diopters, so long as the cylindrical power is appropriately oriented to allow the stripes to be sharply distinguished, and blurring in the perpendicular axis is made acceptable.

[0363] Other combinations may be available: e.g., +1.0 spherical and +1.0 cylindrical, -1.0 spherical and +3.0 cylindrical, or another combination. It should be understood that for most of these combinations, the orthogonal axis will not be in focus, which may confine the optotype (and requested distinguishing selection from the test subject) to patterns and / or distinctions for which only one of two image dimensions is salient.

[0364] A potential advantage of this approach is that amount of magnification of optotype appearance due to the cylindrical corrections in the optical system can be manipulated. This may allow, e.g., a 2-pixel wide stroke which is ordinarily normalized to 1 arc minute to be increased or decreased in apparent size, even if only across one dimension. This potentially allows probing visual acuity to a higher resolution than is available for a fixed pixel-size system. For test subjects for whom a sequence of optotype presentations does not automatically result in an optotype presentation of intermediate resolution, the capability to “synthesize” at least a one-dimensionally controlled test may allow an optical testing system to generate missing data points.

[0365] It is noted that selections of magnification can be made appropriately interact with the cylinder aberration of the optics of the eye of the test subject, insofar as earlier test results have been able to determine it at least approximately. In particular, cylinder power may be introduced by the system at an angle (of the net resulting power) which is off-axis from the total cylindrical aberration of the subject’s eye, but enough modified in magnitude (e.g., increased) to compensate for being off-axis. More particularly, it may be modified to compensate correctly for a specific direction of optical axis (even if other directions are blurred as a result). This has potential benefits to allow alignment of the orientations of the main axes of the pixel grid with the orientation of at least one targeted optical axis which the system and subject eye in combination bring into a well- defined focus for testing. This potentially helps to avoid confounding effects of off-axis distortion of the optotype presentation — e.g., it may help make sure that stripes of an optotype are blurred directly along their length, rather than obliquely.

[0366] Also noted is that continuously adjustable systems and / or methods of introducing a varying degree of cylinder power to the test system are potentially particularly well suited to precise tuning of such a system. Embodiments using the optical arrangements for adjusting cylinder power described, e.g., in relation to Figures 1A-1B, exemplify such systems. Another example, used in some embodiments of the present disclosure, is a tunable lens having a tunable amount of cylinder power.

[0367] At block 2804, in some embodiments, an optotype presentation is shown to the subject. Depending on embodiment and / or how the patient has been instructed, the salient aspect of an optotype presentation may comprise, e.g., its overall shape, its orientation, or both. Optionally, another feature is varied, e.g., luminosity or color, with or without additional instruction to the test subject that the difference is salient. Change of color, for example, may reduce retinal acuity (separately from refractive error); e.g., the distribution of the appropriate visual receptor over the retinal may be less dense for blue cone receptors, and denser for another type of receptor.

[0368] The optotype presentation of block 2804 is understood to comprise a mixture of what can be suitably presented on the pixel grid of a display available to the testing system (e.g., optionally limited to patterns having features with integral pixel sizes), and the effects of the remaining optics of the testing system on how the test subject sees optotype presentation.

[0369] At least under certain conditions (e.g., comprising cylinder adjustment to the optical path), it is presumed that the optotype presentation, considered as a visual acuity target, and particularly with respect to its salient differences from comparison alternatives available to a test subject, will fall in between “ordinary” categories, such as the normal vision threshold of 6 / 6, or the (lower acuity) steps of 6 / 7.5, 6 / 9, and otherwise; or the (higher acuity) steps of 6 / 5, 6 / 4, and otherwise.

[0370] At block 2806, in some embodiments, the test subject provides their response(s) to the optotype presentation. For example, they may make an utterance, press a button, manipulate a cursor, re-address their gaze, or otherwise indicate a selection which is appropriate to their instructions, and / or to the options presented to them.

[0371] At block 2808, in some embodiments, the system uses the response(s), as well as the conditions of the optotype presentation(s) associated with the responses, to determine information about the visual acuity of the test subject. More specifically, any anisotropic magnification effects associated with the optotype presentation are taken into account. This may include adjusting results based on scaling directly, e.g., by directly treating the optotype presentation as though it was scaled in size, according to an axis comprising details of particular salience to the response of the test subject. Additionally or alternatively, the adjusting optionally makes use of “equivalence” calibrations, which determine the meaning of test subject responses according to an estimated overall detectability of stimulus salience. This in turn may be based on responses given, e.g., by previous subjects of known visual acuity (calibration subjects), and / or on simulation results.

[0372] As an example of simulation: an optotype presentation is matched with its conditions of focus and magnification (along with other relevant characteristics) so as to allow producing a simulated version of what a subject (e.g., a subject having a given visual acuity) sees. This simulated version is evaluated for properties such as spatial frequency phase and / or power, which is compared to one or more references, which may represent alternative choices among which a test subject selected to provide a response. For a given threshold of greater similarity to one of these alternatives than for others, it is judged that a test subject will, or will not, be able to make the correct response.

[0373] At block 2810, in some embodiments: as test results are acquired, the system optionally determines a next test condition (comprising an optotype presentation and associated optical settings) to present to the test subject, based at least in part on results of previous tests. This may include an operation of calculating a provisional estimate of the refractive error of the eye(s) of the test subjection, e.g., based on the conditions in which they correctly or incorrectly responded to the optotype presentation.

[0374] Optionally, intermediate results are calculated to a degree sufficient to make selections of following test conditions, but not necessarily at the level of final test results. Immediately, or optionally after other actions as appropriate (e.g., readjustment of the test subject in the test apparatus, additional explanations from the test administrator, or other reasons), the flowchart may be restarted at block 2802.

[0375] Once a stop condition is reached (e.g., there are no more test conditions to present, testing is stopped externally, and / or interim results indicate a sufficient level of confidence and precision in an estimate of the refractive error of the subject’s eye), a final test result is optionally calculated. Alternatively, a previous interim result is used as the final test result.

[0376] At one or both of the stages of interim test result calculations and final test result calculations, an appropriate threshold of visual acuity at which salient features of the optotype presentations used in testing should be distinguishable is used (if already available), or evaluated as appropriate and used. Where relevant, the appropriate threshold includes adjustments based on the settings of variable optical characteristics of the system accompanying how the optotype presentations were presented. In some embodiments, this includes adjustments for magnification anisotropies (z.e., scaling anisotropies) in the optotype presentations. In some embodiments, these scaling anisotropies are introduced as incidental to the inclusion of refractive error corrections in the optical pathway presenting the optotypes to the test subjects. Correcting results for the scaling anisotropies potentially reduces error in test results. In some embodiments, scaling anisotropies are introduced and / or modified according to determinations of what data is useful in the calculating, e.g., to enhance the resolution of refractive error estimates.

[0377] General

[0378] As used herein with reference to quantity or value, the term “about” means “within ±10% of’.

[0379] The terms “comprises”, “comprising”, “includes”, “including”, “having” and their conjugates mean: “including but not limited to”.

[0380] The term “consisting of’ means: “including and limited to”.

[0381] The term “consisting essentially of’ means that the composition, method or structure may include additional ingredients, steps and / or parts, but only if the additional ingredients, steps and / or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

[0382] As used herein, the singular form “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a compound” or “at least one compound” may include a plurality of compounds, including mixtures thereof. The words “example” and “exemplary” are used herein to mean “serving as an example, instance or illustration”. Any embodiment described as an “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and / or to exclude the incorporation of features from other embodiments.

[0383] The word “optionally” is used herein to mean “is provided in some embodiments and not provided in other embodiments”. Any particular embodiment of the present disclosure may include a plurality of “optional” features except insofar as such features conflict.

[0384] As used herein the term “method” refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts.

[0385] As used herein, the term “treating” includes abrogating, substantially inhibiting, slowing or reversing the progression of a condition, substantially ameliorating clinical or aesthetical symptoms of a condition or substantially preventing the appearance of clinical or aesthetical symptoms of a condition.

[0386] Throughout this application, embodiments may be presented with reference to a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of descriptions of the present disclosure. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as “from 1 to 6” should be considered to have specifically disclosed subranges such as “from 1 to 3”, “from 1 to 4”, “from 1 to 5”, “from 2 to 4”, “from 2 to 6”, “from 3 to 6”, etc.; as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0387] Whenever a numerical range is indicated herein (for example “10-15”, “10 to 15”, or any pair of numbers linked by these another such range indication), it is meant to include any number (fractional or integral) within the indicated range limits, including the range limits, unless the context clearly dictates otherwise. The phrases “range / ranging / ranges between” a first indicate number and a second indicate number and “range / ranging / ranges from” a first indicate number “to”, “up to”, “until” or “through” (or another such range-indicating term) a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numbers therebetween. Although descriptions of the present disclosure are provided in conjunction with specific embodiments, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

[0388] It is appreciated that certain features which are, for clarity, described in the present disclosure in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the present disclosure. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

[0389] It is the intent of the applicant(s) that all publications, patents and patent applications referred to in this specification are to be incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually noted when referenced that it is to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present disclosure. To the extent that section headings are used, they should not be construed as necessarily limiting. In addition, any priority document(s) of this application is / are hereby incorporated herein by reference in its / their entirety.

Claims

WHAT IS CLAIMED IS :

1. A system useful to test refractive visual acuity of an eye of a test subject, the system comprising: an optical pathway which presents images comprising optotypes to a retina of the eye; and optical components in the optical pathway leading to the eye, including components which adjust presentation of the optotypes to compensate for refractive error in the eye; wherein adjusting the optical components produces anisotropic scaling of the presentation of the optotypes at the retina; and an acuity calculator, which receives responses of the test subject to the presentations of the optotypes, and calculates visual acuity of the subject using the responses, the calculated acuity also taking into account the anisotropic scaling of the presentation of the optotypes.

2. The system of claim 1, wherein the optical components which compensate for refractive error in the eye include at least one optical cylinder element which modifies the optical cylinder power of the optical pathway.

3. The system of claim 2, wherein the at least one optical cylinder element comprises a plurality of cylinder lenses.

4. The system of claim 3, wherein the plurality of cylinder lenses comprises at least two lenses, having refractive powers of opposite sign.

5. The system of any one of claims 3-4, wherein the plurality of cylinder lenses comprises at least three lenses, arranged along an optical axis of the optical pathway, and including, in order: a first lens with refractive power with a first value, a second lens with refractive power having a value arithmetically signed oppositely to the first value, and a third lens with a refractive power arithmetically signed the same as the first value.

6. The system of any one of claims 1-5, wherein the images comprise pixels projected onto the retina.

7. The system of claim 6, wherein the optical pathway scales each of the pixels to a respective angular display resolution within a range between 0.1 arc minutes and 2 arc minutes.

8. The system of claim 7, wherein the angular display resolution of individuals of the pixels is anisotropically scaled by the adjusting of the optical components.

9. The system of any one of claims 6-8, wherein angular display resolution of at least some of the pixels is different in different directions by at least 5%.

10. The system of any one of claims 8-9, wherein relative angular display resolution of at least some of the pixels varies for different adjustments of the optical components by more than 5%.

11. The system of any one of claims 6-10, wherein an optotype presentation comprises a feature three pixels in width or less, and having an angular display resolution of 1 arc minute or less.

12. The system of claim 11, wherein the feature extends along at least four pixels of the image at about a 45° angle relative to a grid arrangement of the pixels.

13. The system of claim 11, wherein the feature extends along at least four pixels of the image at about a 90° angle relative to a grid arrangement of the pixels.

14. The system of any one of claims 1-13, wherein the acuity calculator determines effect of anisotropic scaling on the calculated visual acuity using predetermined values.

15. The system of claim 14, wherein the predetermined values are predetermined using one or more of the group consisting of:simulated images of optotype presentations, results of acuity tests used as calibration data, and calculations using parameters of the optical pathway.

16. The system of any one of claims 1-15, wherein the system includes a sensor that records the images comprising optotypes as they are generated, and the acuity calculator uses measurements of the images to determine the anisotropic scaling of the presentation of the optotypes.

17. The system of any one of claims 1-16, wherein the system monitors acuity thresholds tested by optotypes presented during testing of the eye; determines adjustments of the optical components which produce anisotropic scaling of a rescaled optotype presentation that allows the system to test an acuity threshold intermediate between the two of the acuity thresholds; and the system make the adjustments and presents the rescaled optotype presentation to the test subject to elicit acuity information about the eye.

18. The system of any one of claims 1-16, wherein: the system selects at least one of the group consisting of: a position of the optotype and an orientation of the optotype based on scaling anisotropy properties of the system.

19. The system of any one of claims 1-17, wherein the system introduces optical distortion along a first image axis of an optotype presentation in order to adjust a magnification of a second image axis of the optotype presentation.

20. A system useful to test refractive visual acuity of an eye of a test subject, the system comprising:an optical pathway which presents images comprising optotypes to a retina of the eye; and wherein the optical pathway produces anisotropic scaling of the presentation of the optotypes at the retina; and an acuity calculator, which receives responses of the test subject to the presentations of the optotypes, and calculates visual acuity of the subject using the responses, the calculated acuity also taking into account the anisotropic scaling of the presentation of the optotypes.

21. The system of claim 20, wherein the system selects the anisotropic scaling by choosing at least one of the group consisting of: a position in the optical field at which the optotype is presented; an orientation of the optotype presentation in the optical field.

22. A method for testing refractive visual acuity of an eye of a test subject, the method comprising: projecting illumination along an optical pathway to project an image comprising at least one optotype on a retina of an eye; and adjusting optical components in the optical pathway leading to the eye to compensate for refractive error in the eye; wherein adjusting the optical components produces anisotropic scaling of the presentation of the optotypes at the retina; receiving responses of the test subject to the presentations of the optotypes; and and calculating, using a processor, visual acuity of the subject using the responses, the calculating taking into account the anisotropic scaling of the presentation of the optotypes.

23. The method of claim 22, comprising adjusting at least one optical cylinder element which is among the optical components which compensate for refractive error in the eye, and adjusting the optical cylinder element modifies the optical cylinder power of the optical pathway.

24. The method of any one of claims 22-23, wherein the images comprise pixels projected onto the retina.

25. The method of claim 24, wherein the adjusting optical components anisotropically scales angular display resolutions of individuals of the pixels.

26. The method of claim 25, wherein relative angular display resolution of the individuals of the pixels varies for different adjustments of the optical components by more than 105%.

27. The method of any one of claims 22-26, wherein the calculating determines effect of anisotropic scaling on the calculated visual acuity using predetermined values.

28. The method of any one of claims 22-27, comprising measuring the images comprising optotypes as they are generated, and using measurements of the images to determine the anisotropic scaling of the presentation of the optotypes.

29. The method of any one of claims 22-28, comprising: monitoring thresholds tested by optotypes presented during testing of the eye; determining adjustments of the optical components which produce anisotropic scaling of a rescaled optotype presentation for testing an acuity threshold intermediate between the two of the acuity thresholds; making the adjustments of the optical components; and presenting the rescaled optotype presentation to the test subject to elicit acuity information about the eye.

30. The method of any one of claims 22-29, comprising introducing optical distortion along a first image axis of an optotype presentation in order to adjust a magnification of a second image axis of the optotype presentation.

Images