Method and system for measuring binocular eye position

Abstract

An embodiment of the present invention includes a method for determining binocular eye position, the method including measuring a separated heterophoria of a first and second eye of a patient at an apparent distance, and determining accommodative convergence of the first and second eyes at the apparent distance using the measured separated heterophoria. In another embodiment, a system for determining binocular eye position includes a stereoscopic display for projecting images onto the first and second eyes, accommodation optics for modifying the projection of the images according to the apparent distance, an eye tracker for tracking the orientation of the first and second eyes, and a computer coupled to the stereoscopic display, accommodation optics, and eye tracker for managing the determination of binocular eye position. [Selected Figure] Figure 6B

Description

[Technical field]

[0001] The present invention relates generally to methods and systems for measuring visual acuity, and more particularly to measuring binocular malalignment. [Background technology]

[0002] With normal vision, an individual can focus on objects located at different distances. Ideally, an individual can focus on distant objects, referred to as distance vision, and on close objects, referred to as near vision. The optical system of the eye uses many muscles to change focus between these distances. These muscles adjust various aspects of the eye when transitioning between distance and near vision. Muscle adjustments include making subtle changes to the shape of the lens to adjust the focus of the lens, rotating the eyeballs to rotate their optical axis, and changing the size of the pupil.

[0003] Presbyopia is a natural deterioration of near vision caused by loss of flexibility of the eye's lens as a person ages. Presbyopia can be partially compensated for by wearing "reading" glasses that correct the near vision refractive error so that the eye does not have to focus as hard when staring at close objects. Presbyopic individuals require different optical corrections for near and distance vision. However, using two glasses and frequently changing them is disturbing. To avoid constantly changing glasses, bifocal glasses can be used that provide different optical corrections for near and distance vision. The transition between these two vision areas can be abrupt or gradual. The latter glasses are called progressive addition lenses (PALs). Abrupt bifocal glasses have a visible line separating the two vision areas, while PALs have no visible line or edge between the areas with different refractive powers.

[0004] Despite all this progress, some types of vision-related discomforts still persist. One of these discomforts is related to the habitual shifts in modern digital lifestyles. A large and growing portion of occupations require workers to spend a large and growing portion of their working time focusing on close-up digital interfaces, including computer screens and mobile devices. The same is true for the personal lives of many who, among other things, play video games for hours and text on cell phones to check for updates. All these occupational and behavioral shifts are exponentially increasing the amount of time people spend gazing at digital screens, devices, displays, and monitors at much closer distances than before. The increased time it takes for the eyes to adjust to the near vision image places excessive demands on the muscles involved in near vision, straining them beyond their comfort zone in many cases. This can lead to fatigue, discomfort, pain, or even digitally induced migraines. To date, there is no widely accepted consensus regarding the detailed causal mechanisms of these digital device-related visual discomfort, pain, and migraines, even though millions of patients experience these pains daily. Thus, there is a need for glasses or other visual solutions that can provide relief from digital ocular discomfort.

[0005] 1-4 show the basic problem of poor binocular alignment. FIG. 1A shows that human vision accommodates in two ways when gazing at a near object, such as the cross shown. First, humans accommodate the refractive power of eyes 1-1 and 1-2 so that a near object at a distance L is imaged on the retina of each eye. This is often called the accommodative response A. Second, humans rotate eyes 1-1 and 1-2 inward by an angle α so that their visual axes 2-1 and 2-2 point to the same near object. This response is often called the accommodative convergence AC. For obvious geometric reasons, the angle α of the accommodative convergence AC with respect to a straight forward reference axis is directly related to the distance L of the accommodative response A, i.e., α=α(L). For a healthy and well-aligned eye, the ratio AC / A of the accommodative convergence AC to the accommodative response A is a geometrically well-defined function that depends on the object distance L and the pupil distance PD of the two eyes.

[0006] 1B-1C show that eyes often exhibit various forms of accommodative misalignment. In FIG. 1B, the two eyes each rotate inward, but to a lesser extent than would be expected from the geometry. As a result, the accommodative convergence angle α is less than what is geometrically required by a misalignment angle β. To explain in some detail, the visual axes of eyes 2-1 and 2-2 must point in a direction that is indicative of a required accommodative alignment to properly view a near object, but instead they rotate inward to a lesser extent and instead point in a direction that is indicative of a relaxed or natural accommodative alignment.

[0007] 1C shows a case where this smaller rotation is asymmetric: in the illustrated case, the visual axis 2-1 of the first eye 1-1 is properly oriented in the direction of the required accommodative position, while the visual axis 2-2 of the second eye 1-2 has rotated inward only to the direction of the relaxed or natural accommodative position with ocular position error by the accommodative position error angle β.

[0008] 2A-2D show some types of accommodative alignment defects. The definitions of alignment defects used by different schools of vision measurement and various monographs show some inconsistencies, and the techniques for characterizing these alignment defects are also varied. Thus, the definitions provided herein are intended to be merely exemplary, and similar and equivalents are also within the scope of the exemplified terms.

[0009] To put the ocular alignment malalignment discussed in this invention into context, we first introduce the concept of fusing images. When human eyes gaze at the same object, each eye generates its own visual perception. These perceptions are transmitted from the eyes to the visual field, where the brain fuses the two images to generate a three-dimensional (3D) perception of the viewed object. This image fusion can be examined using a vision measurement diagnostic system. For example, two separate objects of the same shape can be projected separately into the two eyes using deflectors, prisms, and mirrors, such that the two projections appear to arrive from a single object. These visual perceptions will be fused by the brain into a single perceptual image. The objects projected in this way are called fusible objects that present a fusible image.

[0010] When the experiment increases the distance between the two objects, or increases the deflection angle, or modifies the shape of the objects, the projections into the two eyes begin to differ. At some distance or difference between the objects, the discrepancy between the visual perceptions of the two eyes exceeds a threshold, and the brain stops fusing the two images into a single perception. Objects with such differences in distance, angle, or shape are called unfusible objects that present unfusible images.

[0011] With this preamble, Figures 2A-2D show the concept of fixation mismatch as measured by a testing device often called a Mallet Box. The Mallet Box displays two vertically aligned bars and an "XOX" horizontal "anchor". In some implementations, these two bars can be shifted laterally. In other implementations, an adjustable mirror or prism is placed in front of the patient's eyes to achieve the same horizontal shift. With appropriate selective optics, the anchor and only one of the bars are shown to the first eye 1-1 as the central bar 5-1-c, and the same anchor and only the other bar are shown to the second eye 1-2 as the central bar 5-2-c. The anchor and the central bars 5-1-c and 5-2-c are clearly fusible. Thus, the patient's brain will fuse these images properly without any accommodative eye positioning problems.

[0012] Figure 2B shows that patients with accommodative eye positioning defects will not fuse the images properly. What is typically observed is that the images of the anchor seen by both eyes are fused properly into a single image, but the bar is perceived as shifted. The first eye 1-1 perceives the shifted bar 5-1-s, while the second eye 1-2 perceives the shifted bar 5-2-s. The angle γ between the line to the image center and one of the visual axes 2-1 and 2-2 is called fixation incongruence.

[0013] 2C-2D show a method for measuring the angle required to cancel or compensate for the fixation mismatch. In the system of FIG. 2C, two bars are counter-shifted. A counter-shifted bar 5-1-x is shown for the first eye 1-1 and a counter-shifted bar 5-2-x is shown for the second eye 1-2. The bars are counter-shifted until the patient perceives the two bars as aligned. The angle γ corresponding to these counter-shifts between the visual axis and the line to the counter-shifted bar is *is measured and is typically called the associated heterophoria γ * It is reported as:

[0014] FIG. 3 shows how the fixation mismatch is partially compensated by increasing the partial related phoria. Strictly speaking, the (full) related phoria that completely compensates for the fixation mismatch is given by the intersection of this curve with the partial related phoria axis. If human vision were a purely optical process, the partial related phoria would simply be equal to the negative of the partially compensated fixation mismatch. Thus, the curve would be a straight line passing through the origin and tilted at -45 degrees from the upper left corner to the lower right corner. However, FIG. 3 shows that human vision is rather complicated, in which perception and image processing play a crucial role. FIG. 3 shows four types of relationships between partially compensated fixation mismatch and partial related phoria. Obviously, none of these lines are straight, none pass through the origin, and two of these lines do not even intersect the horizontal axis. These types II and III relationships mean that no amount of partial related phoria can completely compensate for the fixation mismatch. Thus, a substantial challenge remains to determine the relevant heterophoria that fully compensates for the patient's fixation mismatch.We conclude with a brief comment on idiomatic expressions: fixation mismatch when the eyes do not rotate inward to the necessary extent is called "exo", whereas in the rare case where the eyes rotate inward excessively, it is called "eso".

[0015] 4A-4C show a related vision misalignment called split phoria. To characterize split phoria, an experiment similar to that of FIGS. 2A-2D can be performed, with the difference that instead of showing fusible images 5-1 and 5-2, the optometrist shows non-fusible images 6-1-s and 6-2-s for the first eye 1-1 and the second eye 1-2. In FIG. 4A, these non-fusible images are a cross and a bar. As FIG. 4B shows, when the eyes are unable to fuse the images, one or both of the visual axes often rotate outward. In the asymmetric case shown, the visual axis 2-2 of the second eye 1-2 rotates outward by an accommodative misalignment angle δ. This angle of extroversion δ is measured and is called split phoria. In various applications, as described below, the split phoria is distributed evenly across the two eyes, and therefore the split phoria of each eye is equal to δ / 2. In some cases, for example as shown in FIG. 1C, the separation phoria δ may itself be unequally expressed and must be distributed proportionately between the eyes.

[0016] Figure 4C shows a particularly clear case when the field of view of the second eye 1-2 is occluded, with simply no image being presented to the second eye 1-2. This is an extreme case of a non-fusional image. With reference to Figure 4B, in response to the occlusion, the visual axis 2-2 of the second eye 1-2 rotates outward by a measurable separation oblique angle δ.

[0017] As a quantitative characterization of accommodative misalignment, including fixation misalignment and isolated phoria, some physicians use the AC / A ratio affected by misalignment. This AC / A is the ratio of the accommodative convergence angle α-δ / 2 (expressed as a tangent with respect to "prism diopters" Δ) reduced by fixation misalignment, expressed as the refractive power D, divided by the accommodation distance L. A common definition of AC is AC=100tan(α-δ / 2) with respect to prism diopters. For average visual function, an AC / A ratio of 6-6.5Δ / D is required, while surprisingly, in a large segment of the population, AC / A ratios affected by misalignment have been measured at about 3.5Δ / D. Clearly, various forms of accommodative misalignment affect a large percentage of the population, and any progress towards their relief is highly valuable.

[0018] A surprising fact in the corresponding field of optometry is that the relevant and separating phoria angles determined by experienced physicians show a remarkably wide variation. Experiments performed by different optometrists on the same patient, and sometimes even by the same optometrist at different times, report relevant phoria angles expressed in prism diopters Δ with a distribution with a large standard deviation of as much as 3Δ. (1Δ prism diopter corresponds to 1 cm of prism refraction at a distance of 1 meter.) The large variability of these methods makes valid determination and compensation of accommodative malalignment impossible.

[0019] This unusually large standard deviation is sometimes due to several factors, including: (1) the determination methods use the subjective response of the patient as the primary input; (2) some methods use central images while others use peripheral images to determine the relevant heterophoria. The relative accuracy and suitability of these methods have yet to be rigorously evaluated; (3) most physicians use a single measurement or a single method, and therefore do not benefit from the potentially important medical information that can be collected by performing multiple tests; (4) in a previous research project, the applicant has also found that the prismatic response of the eye is quite different in moving test images. However, we are only at the beginning of the process of understanding the relationship of the optimal prismatic correction based on static and moving test images; (5) there are several methods to define prismatic misalignment, which result in predictions and diagnoses of different prisms, but ultimately a single prism must be created in the glasses. It is far from clear how to translate and combine the various diagnostically determined prismatic corrections into a single prism prescription. Applicant is not aware of any significant studies that have evaluated the extent to which the effect and variability of prism prescription depends on the possible combinations of determined prism corrections. Summary of the Invention [Problem to be solved by the invention]

[0020] For all of the above reasons, determining the prism power that optimally compensates for accommodative malposition remains a pressing medical need. [Means for solving the problem]

[0021] To address the above-mentioned medical needs, some embodiments of the present invention include a method for determining binocular eye position, the method including measuring a separated phoria of a first eye and a second eye of a patient at an apparent distance, and determining accommodative convergence of the first eye and the second eye at the apparent distance using the measured separated phoria.

[0022] In another embodiment, a system for determining binocular eye position includes a stereoscopic display for projection of images to a first eye and a second eye, accommodation optics for correcting the projection of the images according to apparent distance, an eye tracker for tracking the orientation of the first eye and the second eye, and a computer coupled to the stereoscopic display, the accommodation optics, and the eye tracker for managing the determination of binocular eye position. [Brief description of the drawings]

[0023] [Figure 1A] FIG. 1 illustrates various accommodative eye position defects. [Figure 1B] FIG. 1 illustrates various accommodative eye position defects. [Figure 1C] FIG. 1 illustrates various accommodative eye position defects. [Figure 2A] FIG. 1 illustrates a method for determining the type of accommodative eye position error. [Figure 2B] FIG. 1 illustrates a method for determining the type of accommodative eye position error. [Figure 2C] FIG. 1 illustrates a method for determining the type of accommodative eye position error. [Figure 2D] FIG. 1 illustrates a method for determining the type of accommodative eye position error. [Diagram 3] FIG. 1 shows four types of relationships between fixation mismatch and segment-related heterophoria. [Figure 4A] FIG. 1 illustrates a method for determining separation oblique angle. [Figure 4B] FIG. 1 illustrates a method for determining separation oblique angle. [Figure 4C] FIG. 1 illustrates a method for determining separation oblique angle. [Diagram 5] FIG. 1 illustrates a system for determining binocular misalignment. [Figure 6A] FIG. 1 illustrates an embodiment of a system for determining binocular eye misalignment. [Figure 6B] FIG. 1 illustrates an embodiment of a system for determining binocular eye misalignment. [Figure 7] FIG. 13 shows an IR image captured by an eye tracker. [Figure 8A] FIG. 1 illustrates an embodiment of a system for determining binocular eye misalignment. [Figure 8B] FIG. 1 illustrates an embodiment of a system for determining binocular eye misalignment. [Figure 9] FIG. 1 illustrates an embodiment of a system for determining binocular misalignment. [Figure 10A] FIG. 1 illustrates an embodiment of an adjustment optical system. [Figure 10B] FIG. 1 illustrates an embodiment of an adjustment optical system. [Figure 11] FIG. 1 illustrates a method for determining binocular misalignment. [Figure 12] FIG. 4 shows exemplary details of the measurement stage. [Figure 13A] FIG. 1 shows steps for carrying out a measurement step. [Figure 13B] FIG. 1 shows steps for carrying out a measurement step. [Figure 13C] FIG. 1 shows steps for carrying out a measurement step. [Figure 13D] FIG. 1 shows steps for carrying out a measurement step. [Figure 14] FIG. 4 illustrates exemplary details of the decision stage. [Figure 15A] FIG. 1 illustrates steps for performing a decision step. [Figure 15B] FIG. 1 illustrates steps for performing a decision step. [Figure 15C-1] FIG. 1 illustrates steps for performing a decision step. [Figure 15C-2] FIG. 1 illustrates steps for performing a decision step. [Figure 16] FIG. 1 illustrates a sub-equatorial embodiment of a method for determining binocular misalignment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The system described in this patent specification addresses the above-specified medical need in at least the following ways: (1) The described system and method determines prism correction solely by objective measurements without subjective input from the patient. This aspect alone significantly reduces the variability of results from patient to patient and physician to physician. In fact, studies on large patient samples using applicant's system and method have determined prism correction with a standard deviation significantly reduced from 3Δ described above to less than 1Δ. This significant reduction in the standard deviation of results alone establishes the method described herein as a quantitatively predictive diagnostic method. (2) The system and method of the present invention uses both central and peripheral test images based on a newly developed understanding of how peripheral and central prism corrections are achieved. Thus, the described system and method is a promising platform for determining an optimal compromise prism prescription that establishes an optimal compromise for compensating for both central and peripheral accommodative misalignment. (3) The described method has two steps, where the final prism correction is determined in the second step based on the critical misalignment information obtained in the first step. Thus, the method integrates knowledge determined by various methods and benefits from information determined by all of them. (4) One of the steps of the method includes moving the test image. Thus, the finally determined prism correction further incorporates and integrates the dynamic prism response of the eye. (5) Due to the robust reproducibility and low variability of the above-mentioned large-scale studies, Applicant's method provides a convincing case for combining the output of various methods in an objective and valid manner to provide an optimized objective single prism correction. These five aspects described herein provide advantages individually and in combination.

[0025] 5-10 show a system 10 for determining binocular eye position, and FIGS. 11-16 show a corresponding method 100 for determining binocular eye position.

[0026] 5 shows that in some embodiments, the system 10 for determining binocular eye position may include a stereoscopic display 20 for projecting a visible image to the first eye 1-1 and the second eye 1-2, accommodation optics 30 for modifying the projected visible image according to the apparent distance, an eye tracker 40 for tracking the orientation of the first eye 1-1 and the second eye 1-2, and a computer 50 coupled to the stereoscopic display 20, accommodation optics 30, and eye tracker 40 for managing the determination of the binocular eye position. In the following, the eyes are labeled as the first eye 1-1 and the second eye 1-2. This labeling may correspond to the left eye and the right eye or vice versa.

[0027] 6A shows a detailed view of some embodiments of the system 10. In some embodiments, the eye tracker 40 may include infrared light emitting diodes or IR LEDs 42-1 and 42-2 located immediately in front of the system 10 for projecting infrared eye tracking beams onto the first eye 1-1 and the second eye 1-2, and infrared light sources 44-1 and 44-2 for illuminating the first eye 1-1 and the second eye 1-2 with infrared imaging light. Both the infrared eye tracking beams and the infrared line imaging light are reflected from the eyes 1-1 and 1-2. The eye tracker 40 may further include infrared (IR) telescopes 46-1 and 46-2 with infrared (IR) cameras 48-1 and 48-2 for detecting the infrared eye tracking beams and the infrared imaging light reflected from the first eye 1-1 and the second eye 1-2.

[0028] Many of the elements of system 10 are included in pairs, e.g., infrared telescopes 46-1 and 46-2. To avoid confusion and for ease of presentation, such element pairs will be referred to by only a leading identifier, such as "infrared telescope 46," which is short for "infrared telescopes 46-1 and 46-2."

[0029] FIG. 7 shows the resulting IR image 49 detected or sensed by the IR camera 48. In this embodiment, there are four separate IR LEDs 42-1, ... 42-4 for each eye. In the description of FIG. 7, to avoid confusion, the "-1" or "-2" designation for a particular eye is omitted. The designations "-1" ... "-4" in this case refer to four IR LEDs all projecting IR eye-tracking beams onto the same eye. The four IR LEDs 42-1, ... 42-4 project four IR eye-tracking beams onto the eye which reflect off the cornea generating so-called Purkinje points P1-1, ... P1-4 in the IR image 49. The designation "P1" refers to reflections from the proximal surface of the cornea. The larger index Purkinje points P2, ... refer to reflections from surfaces located deep within the eye, such as reflections from the proximal and distal surfaces of the ocular capsule. The embodiments described herein utilize the P1 Purkinje point, while other embodiments may use Purkinje points of higher index.

[0030] The reflected IR imaging light of the IR light source 44 is also detected by the IR camera 48. Four Purkinje points P1-1, ... P1-4 superimposed on the detected reflected IR imaging light combine to form an IR image 49 as shown.

[0031] In some embodiments, the eye tracker 40 may include an image recognition system 52 for determining the orientation of the first eye 1-1 and the second eye 1-2 using the detected infrared eye tracking beams forming the Purkinje points P1-1, ... P1-4 and the detected infrared imaging light that combines to form the IR image 49. The image recognition system 52 may, for example, extract an image of the outline of the pupil 3 using an edge recognition method. The image recognition system 52 may then determine the orientation of the eye 1 from the center of the pupil 3. Alternatively, the image recognition system 52 may determine the eye orientation from the Purkinje points P1-1, ... P1-4. Finally, the image recognition system 52 may determine a "best result" orientation using a weighting algorithm by combining the two orientations determined using various known image recognition and image analysis techniques. The image recognition system 52 may be a separate processor, a separate application specific integrated circuit, or may be implemented as software deployed in the system management computer 50.

[0032] 6A-6B further show that the system 10 may include infrared-transmissive visible light mirrors 24-1 and 24-2, one for each eye, for redirecting the projected visible images 26-1 and 26-2 from the stereoscopic display 20 onto the first eye 1-1 and the second eye 1-2, and for transmitting the combined reflected infrared eye-tracking beams and reflected infrared imaging light 45-1 and 45-2 from the first eye 1-1 and the second eye 1-2. In these embodiments, the stereoscopic display screens 22-1 and 22-2 of the stereoscopic display 20 may be positioned around the main optical path of the system 10, and the infrared telescopes 46-1 and 46-2 of the eye tracker 40 may be positioned in the main optical path of the system 10. For reference, in this embodiment, the axis of the accommodation optics lens 34-mirror 24-IR telescope 46 for each eye is generally referred to as the main optical path. Similarly, for clarity, some labeling has been simplified in the figures showing the optical paths and beams.

[0033] 6B shows that in this embodiment, surround stereoscopic display screens 22-1 and 22-2 can project visible images 26-1 and 26-2 into the main optical path of system 10, which are redirected by infrared-transmissive visible-light mirrors 24-1 and 24-2 towards eyes 1-1 and 1-2. At the same time, combined reflected IR eye-tracking beams and reflected IR imaging light 45-1 and 45-2 reflected from eyes 1-1 and 1-2 are transmitted by the same infrared-transmissive visible-light mirrors 24-1 and 24-2 along the main optical path of system 10 towards IR telescopes 46-1 and 46-2.

[0034] FIG. 8A shows another embodiment in which the locations of the stereoscopic display screen 22 and the IR telescope 46 are swapped. FIG. 8B shows that this embodiment can include visible light transmissive infrared (IR) mirrors 24'-1 and 24'-2 for redirecting the combined reflected infrared eye tracking beams and reflected infrared imaging light 45-1 and 45-2 reflected from the first eye 1-1 and the second eye 1-2 towards the IR telescopes 46-1 and 46-2. At the same time, the visible light transmissive infrared mirrors 24'-1 and 24'-2 can transmit the projected visible images 26-1 and 26-2 from the stereoscopic display screens 22-1 and 22-2 of the stereoscopic display 20 to the first eye 1-1 and the second eye 1-2. In these embodiments of the system 10, the stereoscopic display 20 can be positioned in the main optical path of the system 10, and the infrared telescope 46 of the eye tracker 40 can be positioned around the main optical path of the system 10. For reference, in this embodiment, the axis of the accommodation optical system lens 34--mirror 24--stereoscopic display screen 22 for each eye is generally referred to as the main optical path.

[0035] FIG. 9 shows a variation of the system 10 of FIGS. 8A-8B in which the stereoscopic display 20 can include a single stereoscopic display screen 22 and synchronization glasses 28. The synchronization glasses 28 can be shutter glasses or polarized glasses. In this embodiment, both projected visible images 26-1 and 26-2 of the left and right stereoscopic display screens 22-1 and 22-2 of FIGS. 8A-8B are displayed in a fast alternating sequence by the single stereoscopic display screen 22. The synchronization glasses 28 can cooperate precisely with this alternating sequence, allowing the projection of the visible images 26-1 and 26-2 to the first eye 1-1 and the second eye 1-2 in a fast alternating manner, generating the impression that separate images are projected into these eyes. The synchronization glasses 28 can be similar to the 3D glasses used for 3D movie projection and can rely on a liquid crystal LED layer that can rapidly switch the circular polarization of the two lenses of the synchronization glasses 28. Such a system 10 can achieve a small footprint for the system 10, which can be advantageous. For optimal operation, a sufficiently wide field of view for the stereoscopic display screen 22 may be advantageous.

[0036] Some embodiments of the system 10 need not include the mirror 24 or 24'. In these systems, the eye tracker 40 may include a compact implementation of an IR camera 48 placed just in front of the system 10 and tilted at a large enough angle so that the IR camera 48 does not block the projection of the stereoscopic display screen 22. The image recognition system 52 of such an implementation of the eye tracker 40 may include a geometric transformation unit to determine the direction of the eye's visual axis from the substantially tilted IR image 49 and the Purkinje points P1, ...P4, which may even be partially obscured by this tilt.

[0037] In an embodiment of the system 10, the accommodating optics 30 may include phoropter wheels 32-1 and 32-2 having a series of accommodating optics lenses 34-1 and 34-2 of various refractive powers. These accommodating optics lenses 34 are advantageous in simulating apparent distances to the first eye 1-1 and the second eye 1-2.

[0038] As described below with respect to method 100, system 10 can be used to project visual images 26 at different apparent distances to the patient. This projection step can include at least two technical methods. First, the impression that the projected visual image 26 is far or near can be created by inserting an accommodating optics lens 34 with variable refractive power. Second, by projecting visual images 26-1 and 26-2 that are near or far from each other, proper convergence of these images can be simulated, which is another important factor in making these images appear at an apparent distance to the patient.

[0039] In some embodiments, for the first technical method, the adjustment optical system 30 can include a curved mirror, a trial lens, a removable interchangeable lens, an adjustable liquid lens, a deformable mirror, a z-direction movable mirror, a rotating diffractive optical element, a translating diffractive optical element, a variable focus moire lens, or a focusing lens group instead of or in combination with the phoropter wheel 32.

[0040] Figures 10A-10B show that for the second technical method, the accommodation optical system 30 may include a pair of rotatable deflectors 36, rotatable prisms 38, or adjustable prisms 38 (only one of which is shown) for deflecting the projections of images 26-1 and 26-2 to the first eye 1-1 and the second eye 1-2 to simulate the convergence of apparent distance for the first eye and the second eye.

[0041] In some embodiments, convergence can be simulated not by the optical elements described above, but by shifting the projections of visible images 26-1 and 26-2 by stereoscopic display screens 22-1 and 22-2 towards each other, in other words, by projecting these images closer to each other.

[0042] In some systems 10, the accommodation optics 30 and stereoscopic display 20 may be combined into a single light field display including a microlens array, in which case the projected visible images 26-1 and 26-2 shown on the stereoscopic display screens 22-1 and 22-2 may be used in combination with the optical properties of the microlens array to vary the apparent distance of the projected visible images 26-1 and 26-2 as seen by the patient.

[0043] In some systems 10, the accommodation optics 30 and stereoscopic display 20 can be combined into a single light field display that includes a MEMS scanner, focus adjuster, or light source.

[0044] Having described the problems of prismatic or accommodative misalignment and the embodiments of system 10 that have been developed to provide advances in the context of these problems, various methods 100 for determining binocular misalignment using embodiments of system 10 will now be described.

[0045] 11-16 illustrate a method 100 of using the above-described embodiment of the system 10 to determine the binocular position of the eyes 1-1 and 1-2.

[0046] 11 shows that some embodiments of the method 100 may include a step 120 of measuring the separated phoria of the patient's first eye 1-1 and second eye 1-2 at the apparent distance, and a step 140 of determining the accommodative convergence of the first eye 1-1 and second eye 1-2 at this apparent distance using the measured separated phoria. As mentioned above, the method 100 is a two-stage method, and therefore, its results integrate the information and knowledge revealed by the two different stages.

[0047] As described in more detail below, in some embodiments, measuring 120 may include projecting non-fusible visible images 26-1 and 26-2 to the first eye 1-1 and the second eye 1-2 using stereoscopic display 20 of system 10. To more concisely describe method 100, visible images 26-1 and 26-2 of Figures 5-10 are referred to below simply as images 26-1 and 26-2.

[0048] An example of projecting non-fusible images to determine separation heterophoria is described, for example, with respect to Figures 2C-2D. In this case, the two non-fusible images 6-1-s and 6-2-s were of equal appearance or dominance. Some embodiments of method 100 include projecting such non-fusible images of equal dominance.

[0049] In other embodiments, the projecting step can include projecting a dominant image to the first eye 1-1 and a non-dominant image to the second eye 1-2. As described above with respect to Figures 2C-2D, the eye 1-2 that sees the non-dominant image often begins to sway and deviate after the brain's efforts to fuse the two non-fusible images fail. In these embodiments, the measuring step 120 can include tracking the eyes 1-1 and 1-2 with the eye tracker 40 and determining when the swaying eye 1-2 finally reaches a relaxed orientation. Reaching this relaxed state can be inferred, for example, by the eye tracker 40 determining that the movement of the eye 1-2 has slowed below a threshold, changed from directional movement to random micro-oscillations, or stopped. Once the eye tracker 40 determines that the eye 1-2 has reached a relaxed state, the separation heterophoria can be measured by measuring the orientation of at least one of the first eye 1-1 and the second eye 1-2 with the eye tracker 40.

[0050] Figure 12 describes the implementation of these steps in more detail, and Figures 13A-13D show these steps in a specific embodiment. In these embodiments, the measuring step 120 can include the steps of projecting 122 a central image to the first eye with a stereoscopic display at apparent distance vergence, projecting 124 a dispersed image that cannot be fused with the central image to the second eye with a stereoscopic display at apparent distance vergence, tracking 126 a rotation of at least one of the first and second eyes with an eye tracker, identifying a relaxation state from a stabilization of the rotation during tracking 128, and measuring 130 a separation phoria by measuring the orientation of at least one of the first and second eyes in a relaxation state with an eye tracker and a computer.

[0051] The left panel of FIG. 13A shows that the central image projection step 122 can include a step of projecting a central image 201-1, which in this case is a cross, onto the stereoscopic display screen 22-1 of the stereoscopic display 20 of the system 10. The projection step 122 can be performed at the apparent distance vergence 206. A reference axis 202-1 for reference is introduced as a central normal connecting the center of the first eye 1-1 and the center of the stereoscopic display screen 22-1. Using this reference axis 202-1, the apparent distance vergence 206 can be characterized by the angle of apparent distance vergence α=α(L) that the visual axis 204-1 of the first eye makes with the reference axis 202-1 when gazing at an object located midway between the two eyes 1-1 and 1-2 at the location of the apparent distance L. More generally, the apparent distance convergence 206 will be represented by and will be referred to as a line pointing from the center of the first eye 1-1 at an angle α(L) relative to the reference axis 202-1, even if the visual axis 204-1 of the first eye is not oriented along this line.

[0052] The central image 201-1 is central in the sense that it is displaced from the center of the stereoscopic display screen 22-1 only by an apparent distance vergence angle α(L) to simulate the apparent distance vergence 206. For simplicity, this angle is sometimes referred to simply as the vergence angle α. The definition of the first eye's visual axis 204-1 can incorporate the lens or other relevant portion of the accommodation optics 30-1 that the first eye 1-1 views when it is focusing on the central image 201-1.

[0053] The right panel of Fig. 13A shows the projection step 124 of a dispersed image, in this case a randomly placed ball with no apparent center or a set of spheres of random size and position, to the second eye 1-2. The central image 201-1 is an example of a dominant image, and the dispersed image 201-2 is an example of a non-dominant image. The central dominant image 201-1 and the dispersed non-dominant image 201-2 are examples of non-fusible images. Alternatively, instead of the randomly placed balls, the stereoscopic display screen 22-2 can simply be darkened as in Fig. 4C as another embodiment of the non-fusible dispersed image 201-2.

[0054] 13B shows that the second eye 1-2 will also initially rotate inward through approximately the same apparent distance vergence angle α as the first eye 1-1, but will then rock away after the brain fails to fuse the non-fusible central image 201-1 and the dispersed image 201-2. The eye tracker 40 can perform a tracking step 126 of the second eye 1-2 until the optometrist or an automated program determines from the stabilization of the tracking rotation in a discrimination step 128 that the rocking second eye 1-2 has reached a relaxed state. This stabilization can be defined in various ways, i.e., the eye stops, the amplitude of the eye's micro-oscillations falls below a threshold, or the eye's directional rotation transitions to a non-directional rocking.

[0055] Once the flaccid state is identified in step 128, the eye tracker 40 can measure the orientation of the flaccid second eye 1-2 in a measurement step 130 by determining the angle δ between the visual axis 204-2 of the second eye and the apparent convergence 206. In this measurement step 130, the angular discrepancy δ of the flaccid second eye 1-2 from the apparent distance convergence 206 is referred to as the separation phoria 208 of the separation phoria angle δ. This definition is very similar to that described in Figures 4B-4C. As mentioned above, there are small differences between the separation phoria definitions of various practitioners.

[0056] In some related embodiments, tracking 126 may include tracking rotations of the first eye 1-1, the second eye 1-2, or both. In these embodiments, the separation phoria 208 may be defined by measuring 130 an associated phoria angle δ-1 of the first eye, an associated phoria angle δ-2 of the second eye, and determining the separation phoria δ as some type of average of δ-1 and δ-2.

[0057] 13A-13B show that steps 122-130 of the entire measurement step 120 can be performed for a near vision distance, for example L in the range of 40 cm to 100 cm.

[0058] 13C-13D show that the same steps 122-130 can be performed as part of a distance vision test when the apparent distance L is large and the apparent distance convergence angle α is α=0. In a related embodiment, L can be in the range 1 m to 10 m. Expressed in diopters, the method 100 can be performed with near vision distances corresponding to 1-3D and far vision distances corresponding to 0-0.5D.

[0059] In summary, the result of the first stage of the method 100, the measuring step 120, is a separation phoria 208 with a separation phoria angle δ. The second stage of the method 100, the determining step 140, performs an additional test for prismatic misalignment based on the previously determined separation phoria 208. The overall method 100 is thus a combination of the first and second stages, whereby the method 100 integrates two distinctly different tests for prismatic misalignment and thus integrates knowledge and data on two different types of binocular alignment, thereby ensuring a qualitatively more complete treatment and a qualitatively better improvement of vision.

[0060] Figure 14 shows that the determination step 140 can include a presentation step 142 using a stereoscopic display of a first image to a first eye and a second image to a second eye with apparent distance convergence corrected using the measured separation heterophoria, and the first and second images can be fused.

[0061] FIG. 15A shows that in some implementations of the presenting step 142, a fusible first image 210-1 can be presented to the first eye 1-1 on a stereoscopic display screen 22-1, and a fusible second image 210-2 can be presented to the second eye 1-2 on a stereoscopic display screen 22-2. These fusible images 210-1 and 210-2 can be ambient. For example, the ambient images 210-1 and 210-2 can be two substantially equal bands or rings consisting of a ball or planet as shown. The centers of the fusible images 210-1 and 210-2 can be shifted towards each other according to the apparent distance convergence 206 corrected for the convergence angle α by the separation phoria δ (208) measured in the measuring step 120. The measured separation phoria δ can be distributed symmetrically between the two eyes as δ / 2-δ / 2 as shown. In these typical cases, the centers of the fusible images 210-1 and 210-2 can be shifted toward each other according to a convergence angle α-δ / 2, corrected by separation phoria δ relative to the reference axes 202-1 and 202-2. Thus, the visual axes 204-1 and 204-2 of the first and second eyes typically align with apparent distance convergence 206 corrected by separation phoria 208, as shown by their visual axes 204 pointing toward the center of the fusible images 210.

[0062] In some cases, when the binocular malalignment of the two eyes is asymmetric, the optometrist may decide to distribute the measured separation heterophoria δ unequally between the two eyes. It should also be noted that the above idiomatic expressions will remain unchanged hereafter to facilitate the present description, and that in this description, the pair of "Limiting Condition N-1 and Limiting Condition N-2" will be written as "Limiting Condition N" for simplicity, when it is not confusing.

[0063] The shift of the fusible image 210 can be influenced by the accommodation optics 30. The setting of the accommodation optics 30 can depend on L, the accommodation distance, or on the patient's preferred spectacle power, sometimes further corrected with cylinder lenses or aberrations.

[0064] In some embodiments, the first fusible image 210-1 and the second fusible image 210-2 can be dynamic. In FIG. 15A, the directed dashed arcs indicate that the planet's ring can be rotated around its center. Experiments have shown that the ambient prism effect is captured more reliably and reproducibly by rotating the ambient fusible images 210. The radius, spatial distribution, color scheme, dynamics, and rotation speed of these fusible images 210 can all be adjusted in the presentation stage 142 to provide optimally weighted eye position information.

[0065] In some embodiments, the first image 210-1 and the second image 210-2 may be static. In some embodiments, the first image 210-1 and the second image 210-2 may be centered. These embodiments may present unique advantages.

[0066] Fig. 14 explains that the presentation step 142 can be followed by a projection step 144, which is shown in Fig. 15. The projection step 144 can include a projection step of a first additional central image 212-1 to the first eye 1-1 and a projection step of a second additional central image 212-2 to the second eye 1-2. These central images 212 can be projected at the center of the fusible image 210. In an embodiment of a planet on which the fusible image 210 orbits, the additional central image 212 can be projected, for example as a cross, at the center of the planet orbit as shown.

[0067] The projection step 144 of these two additional central images 212-1 and 212-2 can be performed in an alternating manner using the stereoscopic display 20. In Fig. 15B, the cross 212-1 is shown in solid lines and the other additional central image 212-2 is shown in dashed lines to represent the alternating manner of the projection step 144 of only one of the additional central images. The period of the alternation can be selected according to several different criteria and can be less than 1 second, in the range of 1 to 100 seconds, and in some cases in the range of 5 to 10 seconds.

[0068] If the angle δ of separation phoria 208 measured in step 120 completely captures the binocular position of eye 1, then eye 1 would no longer need to accommodate the projection step 144 of an additional central image 212 using the convergence angle α corrected by the separation phoria angle δ / 2. This would be manifested by the visual axis 204 of the eye remaining aligned at the convergence angle α corrected by the separation phoria angle δ / 2 after the projection step 144.

[0069] However, Applicant's research has revealed that patients move and accommodate their eye 1 in response to the projection 144 of an additional central image 212 by a corrected convergence angle α-δ / 2. This has led Applicant to the realization that additional measurements are needed to determine the residual prismatic misalignment of the eye. These additional measurements are described as follows in steps 146-154: using an eye tracker to track the accommodation of the first eye in response to the projection of a first additional central image and to track the accommodation of the second eye in response to the projection of a second additional central image; using a stereoscopic display and a computer to project in an alternating manner a first additional central image shifted by a first iterative associated phoria to reduce the accommodation of the first eye and a second additional central image shifted by a second iterative associated phoria to reduce the accommodation of the second eye; using an eye tracker to track the accommodation of the first eye in response to the projection of the shifted first additional central image and a second additional central image shifted by a second iterative associated phoria to reduce the accommodation of the second eye; These steps are then described in some detail: step 150 of tracking accommodation of the second eye in response to the projection of the second additional central image, step 152 of determining whether the effective accommodation of the first and second eyes is less than the accommodation threshold and returning to projecting the shifted first additional central image if the effective accommodation of the first and second eyes is greater than the accommodation threshold, step 154 ​​of identifying a stabilized associated phoria with the last first iterative associated phoria and the last second iterative associated phoria if the effective accommodation of the first and second eyes is less than the accommodation threshold, and step 156 of identifying the sum of the separated phoria and the stabilized associated phoria as a correction to the accommodative convergence corresponding to the apparent distance. These steps will now be described in some detail.

[0070] FIG. 14 illustrates, and FIG. 15B shows, that the projection stage 144 can be followed by a tracking stage 146 of the accommodation of the first eye 1-1 in response to the projection of a first additional central image 212-1 and a tracking stage 146 of the accommodation of the second eye 1-2 in response to the projection of a second additional central image 212-2, using the eye tracker 40, in order to determine the residual prismatic misalignment. FIG. 15B shows that the first eye 1-1 accommodates with respect to the projection stage 144 by rotating the visual axis 204-1 of the first eye with a first eye accommodation angle 214-1 denoted by ε-1, and the second eye 1-2 accommodates with a second eye accommodation angle 214-2 denoted by ε-2, by rotating the visual axis 204-2 of the second eye. Here, for the sake of simplicity, these angles refer to the apparent distance vergence corrected by the separation heterophoria with the angle α-δ / 2 instead of the reference axis 202. The adjustment angles ε-1 and ε-2 were found to be non-zero, necessitating the subsequent step of decision step 140.

[0071] 15C-1, 15C-2 show that the stage 140 of determining accommodative convergence then includes a stage 148 of projecting a first additional central image 212-1 shifted by a first iteratively related oblique angle φ(n)-1 to reduce the accommodation of the first eye 1-1, and a second additional central image 212-2 shifted by a second iteratively related oblique angle φ(n)-2 to reduce the accommodation of the second eye 1-2. In this case, the accommodation of the eye can be measured by the change in the accommodation angle ε(n)-1, which will be described in detail below.

[0072] For clarity and simplicity, in these Figs. 15C-1, 15C-2, only the first eye 1-1 is specified. The shifted additional central image 212 is connected to the eye 1 and is characterized by a shifted image axis 216. Figs. 15C-1, 15C-2 show a first shifted image axis 216-1 that connects the first shifted additional central image 212-1 to the first eye 1-1.

[0073] With reference to Figures 2-3, the fixation mismatch γ and the associated heterophoria γ needed to compensate for it *It has been noted that the associated phoria φ(n)−1 is not simply equal and opposite to the accommodation angle ε(n)−1 of the first eye. Recognizing this, the embodiment of the method 100 therefore iteratively determines these quantities in stages 1, 2, ... n. The above definitions refer to the stage indices as φ(n)−1 and ε(n)−1, with the first iterative associated phoria of the first round being denoted as φ(1)−1, the second iterative associated phoria of the first round being denoted as φ(1)−2, and so on. Of course, the indices "-1" and "-2" successively label the angles of the first eye 1-1 and the second eye 1-2, respectively, while the indices "(1)", "(2)", ... "(n)" label the first, second, and nth stages of the iterative process.

[0074] As with the projection step 144, the projection step 148 of these shifted additional central images 212-1 and 212-2 can be performed in an alternating manner using the stereoscopic display 20 and the computer 50.

[0075] 15C-1 and 15C-2 further illustrate that the projection step 148 can be followed by a tracking step 150 of the accommodation of the first eye 1-1 in response to the projection step of the shifted first additional central image 212-1, and a tracking step 150 of the accommodation of the second eye 1-2 in response to the projection step of the shifted second additional central image 212-2, using the eye tracker 40. When specifying the presentation to the first eye 1-1 only, the tracking step 150 includes a tracking step of the accommodation angle ε(n+1)-1 of the first eye 1-1 in response to the projection step 148 of the first additional central image 212-1 shifted by the first iteratively related oblique angle φ(n)-1.

[0076] This tracking stage 150 is similar to the tracking stage 146. The tracking stage 150 is distinguished by an iteration stage index that has increased from (n) to (n+1). Briefly, the embodiment of the method includes shifting the additional central image 212 by an iterative associated oblique angle φ(n), tracking a reactive accommodation angle ε(n+1) of the eye 1, determining the accommodation of the eye 1 from the change in the accommodation angle ε(n+1)-ε(n), and then repeating the shifting of the additional central image 212 by a new iterative associated oblique angle φ(n+1) whose magnitude and sign are selected to reduce the change in the accommodation angle ε(n+1)-ε(n).

[0077] In some embodiments, the magnitude of φ(n+1)-φ(n) can be selected to be equal to ε(n+1)-ε(n), i.e., |φ(n+1)-φ(n)|=|ε(n+1)-ε(n)|. In some cases, these embodiments can exhibit slow convergence. Thus, in some embodiments, |φ(n+1)-φ(n)| can be selected to be equal to λ|ε(n+1)-ε(n)|, i.e., |φ(n+1)-φ(n)|=λ|ε(n+1)-ε(n)| when λ<1. These embodiments often exhibit good convergence. In various embodiments, other nonlinear, polynomial, non-analytical, or analytical relationships can be used.

[0078] After performing these steps 148 and 150 iteratively, a decision step 152 can be performed to determine whether the effective accommodation of the first and second eyes is less than the accommodation threshold. Using the framework described above, the decision step 152 can evaluate whether the change in accommodation angle |ε(n+1)-ε(n)| is less than the threshold. Effective accommodation can be defined in a variety of ways. This definition can include the change in accommodation angle of only one of the eyes, i.e., |ε(n+1)-ε(n)| for eye 1-1, or the sum of the change in accommodation angle for both eyes 1-1 and 1-2, or some weighted average, or a non-linear relationship.

[0079] If the change in the adjustment angle |ε(n+1)−ε(n)| is greater than a threshold, the method can return to the projection step 148 of the shifted first additional central image 212 shown in FIGS. 15C-1 and 15C-2.

[0080] On the other hand, if in step (n) it is found that the accommodation of the eye, characterized for example by the change in the accommodation angle |ε(n+1)−ε(n)|, is smaller than a threshold value, the iterations can be stopped and the method can continue with a step 154 ​​of identifying the stabilized associated phoria φ at the last first iterative associated phoria φ(n)−1 and the last second iterative associated phoria φ(n)−2. As in the above case, a different formula can be used to determine the stabilized associated phoria φ in this step 154, for example φ=(φ(n)−1)+(φ(n)−2).

[0081] In conventional embodiments, the separation phoria δ and the associated phoria φ are generally defined relative to the two eyes, so that in the symmetric case the monocular values ​​are half the angles defined here.

[0082] The identification step 154 ​​can be followed by an identification step 156 of a correction to the accommodative convergence AC with an accommodative convergence angle α corresponding to the apparent distance of the sum of the separated phoria δ and the stabilized related phoria φ (δ+φ). This allows the complete or completely corrected accommodative convergence determined by the method 100 to be expressed in terms of prism diopters Δ by the tangent of the corresponding complete or completely corrected accommodative convergence angle [α-(δ+φ) / 2]. As mentioned above, the typical definition of accommodative convergence is AC=100tan[α-(δ+φ) / 2] in prism diopters Δ. This formula shows one of the ways in which the result of the embodiment of the method 100 is a clear advancement compared to the conventional method in which only the separated phoria δ is used to correct α, i.e., AC=100tan[α-δ / 2]. Another difference compared to the conventional method is the particular system 10 and method 100 that determine δ.

[0083] Once the fully corrected AC has been determined by method 100, to characterize the binocular eye position, it can again be characterized by an AC / A ratio, which is the ratio of the accommodative convergence AC to the accommodative response A. This AC / A ratio can be determined for a single distance or can be formed from values ​​of AC and A for multiple distances. For simplicity, the fully corrected accommodative convergence AC is referred to herein simply as accommodative convergence AC.

[0084] In some embodiments, the method 100 includes determining the apparent distance L d The accommodative convergence resulting from the step of performing the method 100 at the location of d ) and the stage for determining the apparent distance L n The accommodative convergence resulting from the step of carrying out the method at the location of near vision accommodative convergence AC(L n and determining a

[0085] With these preliminary steps in mind, in some embodiments, the distance vision accommodation response A (L d ) and near vision accommodation response A (L n ) in diopters, and then the distance vision accommodative convergence AC (L d ) to near vision accommodative convergence AC(L d ) is subtracted from the distance vision accommodation response A(L d ) to near vision accommodation response A (L n By constructing the ratio of the first eye to the second eye divided by the second eye minus the first eye, the binocular position of the first eye and the second eye can be characterized as: Binocular position = [AC(L d )-AC(L n )] / [A(L d )-A(L n )] (1)

[0086] In some embodiments, the measuring 120 at the apparent distance and the determining 140 at this apparent distance can be performed using the adjustment optics 30.

[0087] When discussing the shortcomings of existing methods above, the subjectivity of patient feedback was noted as one source of scatter in the data and a reason for limited repeatability. In this regard, embodiments of method 100 can be performed without requiring a substantial response from the patient to determine one of the critical quantities or angles. (Of course, non-substantial responses, e.g., regarding comfort, can be part of method 100 without issue.) This is one of the main reasons why method 100 produces measurements with high repeatability.

[0088] FIG. 16 illustrates that in some embodiments, when method 100 is performed using an apparent distance corresponding to near vision, the separated heterophoria and accommodative convergence corresponding to near vision can be determined at a visual angle below the equatorial direction 9 by displaying a central image 201 below the equatorial direction 9.

[0089] The applicant's extensive experimentation has demonstrated that when prism glasses are manufactured based on the accommodative convergence determined by method 100, patients wearing the glasses have reported particularly promising relief from digital device-related vision discomfort, pain, and migraines.

[0090] This substantial improvement is most likely due to, among other things, the fact that method 100 develops and integrates methods relating to points (1)-(5) above as follows. (1) Method 100 does not use the patient's subjective response as a primary input. (2) The method 100 uses both peripheral images, e.g., images 124 and 210, and central images, e.g., images 201 and 212. (3) Method 100 uses a two-stage approach, having a measurement stage 120 and a decision stage 140, to collect and utilize information regarding both central and peripheral vision. (4) The method 100 uses a moving inspection image, for example, image 210 . (5) Method 100, for example, in steps 142-156, develops a specific definition of accommodative convergence and a protocol for determining it, and has demonstrated through extensive testing that eyeglasses prescribed using this definition are particularly effective at relieving eye strain-related discomfort.

[0091] For all of the above reasons, the above-described system 10 and method 100 provide a promising new approach to relieving eye strain-related discomfort, pain, and migraines.

[0092] While the present application includes many embodiments, these should not be construed as limitations on the scope of the invention or what may be claimed, but as descriptions of features unique to particular embodiments of the invention. Certain features described in the application in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment can also be implemented in the embodiment separately or in any suitable subcombination. Furthermore, although features may have been described or originally claimed above as functioning in certain combinations, in some cases one or more features from a claimed combination can be excluded from the combination, and the claimed combination can be a subcombination or a variation of a subcombination. [Explanation of symbols]

[0093] 1-1 The First Eye 1-2 The Second Eye 10. System for determining binocular eye position 32-1, 32-2 Phoropter Wheel 34-1, 34-2 Adjustment optical system lens

Claims

1. 1. A method for determining binocular eye position, comprising: a measuring step for measuring the separated heterophoria of the first and second eyes of the patient at an apparent distance; determining an accommodative convergence of the first eye and the second eye at the apparent distance using the measured separation phoria; wherein the determining step comprises: presenting, using a stereoscopic display, a first image to the first eye and a second image to the second eye with the apparent distance convergence corrected using the measured separation heterophoria, the first image and the second image being fusible and the first image and the second image being of the surroundings; in an alternating manner using the stereoscopic display, projecting a first additional central image as a first central image to the first eye; projecting a second additional central image as a second central image to the second eye; tracking an accommodation of the first eye using an eye tracker in response to projection of the first additional central image; and tracking an accommodation of the second eye using the eye tracker in response to projection of the second additional central image; The determining step comprises: using the stereoscopic display and the computer in an alternating manner, projecting a first additional central image shifted by a first iterative associated phoria to reduce the accommodation of the first eye orientation; projecting a second additional central image shifted by a second iterative associated phoria to reduce said accommodation of said second eye orientation; tracking an accommodation of the first eye using the eye tracker in response to the projection of the shifted first additional central image; tracking an accommodation of the second eye using the eye tracker in response to the projection of the shifted second additional central image; determining whether the accommodation of the first and second eye orientations is less than an accommodation threshold; returning to the step of projecting the shifted first additional central image if the accommodation of the first and second eye orientations is greater than the accommodation threshold; identifying a stabilized associated phoria from the last first repetitive associated phoria and the last second repetitive associated phoria when the accommodation of the first and second eye orientations is less than the accommodation threshold; The method of claim 1, further comprising:

2. The measuring step includes: projecting non-fusible images to the first eye and the second eye using a stereoscopic display; Including, 2. The method of claim 1 .

3. The projection step comprises: projecting a dominant image to the first eye; projecting a non-dominant image to the second eye; Including, 3. The method of claim 2 .

4. The measuring step includes: measuring the separated phoria by measuring an orientation of at least one of the first eye and the second eye in a relaxed state using an eye tracker; Including, 3. The method of claim 2 .

5. The measuring step includes: projecting a central image to the first eye with apparent distance vergence using a stereoscopic display; projecting a dispersed image to the second eye with the stereoscopic display at an apparent distance convergence, the central image and the dispersed image being non-fusible; and tracking a rotation of at least one of the first eye and the second eye using the eye tracker; identifying a relaxation state from stabilization of the tracked rotations; measuring the separated phoria by measuring an orientation of at least one of the first eye and the second eye in the relaxed state using the eye tracker and computer; Including, 2. The method of claim 1 .

6. the first image and the second image are dynamic; 2. The method of claim 1 .

7. the first image and the second image are static; 2. The method of claim 1 .

8. The determining step comprises: identifying the sum of the separated phoria and the stabilized related phoria as a correction to the accommodative convergence corresponding to the apparent distance; Including, 2. The method of claim 1 .

9. using a ratio of said accommodative convergence to accommodative response to characterize said binocular eye position; 9. The method of claim 8, comprising:

10. determining distance vision accommodative convergence as the accommodative convergence resulting from performing the method at distance vision apparent distance; and determining near vision accommodative convergence as the accommodative convergence resulting from performing the method at near vision apparent distance; 2. The method of claim 1 .

11. determining a distance vision accommodative response and a near vision accommodative response; constructing a ratio of the distance accommodative convergence minus the near accommodative convergence divided by the distance accommodative response minus the near accommodative response to characterize the binocular position of the first eye and the second eye; 11. The method of claim 10, comprising:

12. The step of determining near vision accommodative convergence comprises: determining said near accommodative convergence at a viewing angle below the equator; Including, 11. The method of claim 10.

13. The measuring step at the apparent distance and the determining step at the apparent distance are performed using adjustment optics.

2. The method of claim 1 .

14. performing the method without soliciting a response from the patient; 2. The method of claim 1 .

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