Boresight recognition system and method

Abstract

The apparatus and methods described herein provide improved methods for accurately identifying and locating the visual axis of an eye and its intersection with the iris plane. In one embodiment, a visual axis identification system includes a fixation light source, a camera, and a processing system. During its operation, a patient focuses their gaze onto two or more fixation spots provided by the fixation light source on its optical axis, where these spots produce two or more corresponding images on or near the patient's retina. The patient's head is then relatively rotated while the patient continues to maintain their gaze on these fixation spots. When the centers of these multiple images coincide within the patient's field of view, the patient's visual axis can be located by determining the position of the optical axis of the fixation light source relative to the patient's eye.

Description

BACKGROUND TECHNICAL FIELD

[0002] Embodiments of the present disclosure relate generally to ophthalmic methods and apparatus for characterizing optical properties of an eye, and more particularly to methods and apparatus for accurately identifying the visual axis of an eye. BACKGROUND

[0004] Conventional techniques for presbyopia treatment often involve determining the relative position of the visual axis of a patient's eye. Accurate determination of the visual axis is critical for effective placement of bifocal, multifocal, and extended depth of focus (EDOF) intraocular lenses (IOLs). Even slight misalignment of these lenses can significantly impede any benefits expected from their surgical implantation. Other examples of presbyopia treatments that can benefit from visual axis determination include, for example, LASIK, PresbyLASIK, or multifocal LASIK, and photorefractive keratectomy (PRK) surgery, among others.

[0005] The visual axis is the actual line of sight of a person, and it is the straight line connecting the fovea, a small pit in the retina, and the point of sharpest vision with a fixated light source. Thus, locating the visual axis and its intersection with the iris plane is critical for determining the position of an IOL, as even slight misalignment can significantly impede its functionality. Currently, there are no diagnostic devices for accurately and precisely determining the visual axis position. Instead, the position of the visual axis through the iris plane is often approximated as the midpoint between the pupil center and the corneal vertex, or the first Purkinje image, which is the reflection of the fixated light on the outer surface of the cornea. This approach is often inaccurate, as the visual axis can be located at a position away from the above-mentioned midpoint, especially in damaged or abnormally shaped eyes.

[0006] Accordingly, there is a need in the art for improved methods and apparatus for identifying the visual axis of an eye. SUMMARY

[0007] The present disclosure relates generally to methods and apparatus for accurately identifying the visual axis of an eye.

[0008] In certain embodiments, a method for determining a position of a visual axis of a patient's eye is provided. The method includes directing a fixation light toward the patient's eye, where the fixation light has two or more fixation light spots formed at different positions along an optical axis of the fixation light source, the fixation light spots corresponding to two or more images formed on or near a retina of the patient's eye. One or more digital images of an iris plane of the patient's eye are captured by a first camera while the center of the two or more images formed on or near the retina coincides within the patient's field of view and simultaneously while an optical center of the first camera is aligned with the optical axis of the fixation light source. A visual axis point position at the iris plane is then identified based on the one or more digital images, where the visual axis point position corresponds to an X / Y position of the optical center of the first camera relative to an X / Y position of the patient's eye shown in the one or more digital images. BRIEF DESCRIPTION OF DRAWINGS

[0009] So that the manner in which the above recited features of the present disclosure can be understood in detail, a brief description of the

[0010] Figure 1 A schematic cross-sectional top view of a human eye is shown.

[0011] Figure 2 A front view of a human eye is shown.

[0012] Figure 3 A schematic view of a visual axis identification system according to certain embodiments of the present disclosure is shown.

[0013] Figure 4A And Figure 4B A schematic view of an eye focusing on multiple fixation light points according to certain embodiments of the present disclosure is shown.

[0014] Figure 5A And Figure 5B A schematic view of an eye focusing on multiple fixation light points according to certain embodiments of the present disclosure is shown.

[0015] Figure 6A And Figure 6B A schematic view of a multiplexer element within a fixation light source according to certain embodiments of the present disclosure is shown.

[0016] Figure 7 A schematic view of an exemplary multiplexer element that can be used in conjunction with the visual axis identification system of Figure 3 according to certain embodiments of the present disclosure is shown.

[0017] Figure 8This demonstrates the compatibility with certain embodiments of the present disclosure. Figure 3 A schematic diagram of an exemplary multiplexer element used in conjunction with a line-of-sight recognition system.

[0018] Figure 9 This demonstrates the compatibility with certain embodiments of the present disclosure. Figure 3 A schematic diagram of an exemplary multiplexer element used in conjunction with a line-of-sight recognition system.

[0019] Figure 10 This demonstrates the compatibility with certain embodiments of the present disclosure. Figure 3 A schematic diagram of an exemplary multiplexer element used in conjunction with a line-of-sight recognition system.

[0020] Figure 11 This demonstrates the compatibility with certain embodiments of the present disclosure. Figure 3 A schematic diagram of an exemplary multiplexer element used in conjunction with a line-of-sight recognition system.

[0021] Figure 12 This demonstrates the compatibility with certain embodiments of the present disclosure. Figure 3 A schematic diagram of an exemplary multiplexer element used in conjunction with a line-of-sight recognition system.

[0022] Figure 13A and Figure 13B This demonstrates the compatibility with certain embodiments of the present disclosure. Figure 3 A schematic diagram of an exemplary multiplexer element used in conjunction with a line-of-sight recognition system.

[0023] Figure 14A and Figure 14B Certain embodiments according to this disclosure are illustrated. Figure 3 A schematic diagram of the line-of-sight recognition system.

[0024] Figure 15A and Figure 15B This demonstrates, according to certain embodiments of the present disclosure, that the eye focuses on a point... Figure 3 and Figures 14A-14B A schematic diagram of multiple fixed-viewpoints generated by the visual axis recognition system.

[0025] Figure 16 The use of certain embodiments of this disclosure is illustrated. Figure 3 The method of the visual axis recognition system involves generating an eye-view image from a camera.

[0026] Figures 17A-17E The use of certain embodiments of this disclosure is illustrated. Figure 3 and Figures 14A-14B The representation of the patient's visual field during the visual axis recognition system, and the system used to generate the above representation.

[0027] Figure 18 A schematic diagram of a system for identifying a visual axis of an eye is shown. Figure 3 A schematic diagram of a system for identifying a visual axis of an eye is shown.

[0028] Figure 19 A flowchart of a method for identifying a visual axis of an eye is shown. Figure 3 Figures 14A-14B A flowchart of a method for identifying a visual axis of an eye is shown. Figure 18 A flowchart of a method for identifying a visual axis of an eye is shown.

[0029] For purposes of clarity, identical reference numerals have been used, where possible, to designate identical elements common to the figures. It is contemplated that elements and features of one embodiment can be beneficially incorporated into other embodiments without further recitation. DETAILED DESCRIPTION

[0030] The present disclosure relates generally to methods and apparatus for identifying a visual axis of an eye.

[0031] Generally, the refractive surfaces of an eye (e.g., the anterior and posterior surfaces of the cornea and lens) are not centered on the same line (e.g., an axis), and the lens is tilted with respect to the gaze of the eye. Due to the lack of rotational symmetry, the eye does not have a true optical axis. However, the eye does have a visual axis, which is the line connecting a fixated object and the fovea of the eye. The center of the visual field of the eye is focused on the fovea, where cone cells are particularly concentrated, and thus, vision is highest in the direction of the visual axis. Optical models show that a multifocal LASIK treatment should be centered on the visual axis with an accuracy of about 50 pm to avoid a decrease in vision. Thus, it is important to accurately and precisely identify the visual axis of an eye for presbyopic LASIK surgery and many other ophthalmic refractive procedures, such as positioning a multifocal accommodating lens.

[0032] There are currently no devices that can accurately identify and locate the visual axis. Instead, medical practitioners, such as ophthalmologists, typically approximate the location of the visual axis through the iris plane as being at the midpoint between the center of the pupil and the first Purkinje image. However, this approximation is often inaccurate, particularly for damaged or abnormally shaped eyes. The devices and methods described herein provide improved methods for accurately identifying and locating the visual axis of an eye and its intersection with the iris plane. Embodiments of the present disclosure can be used for correcting lens alignment as well as other ophthalmic procedures, including ophthalmic refractive procedures such as multifocal LASIK or multifocal PRK surgery.

[0033] ​In one embodiment, a visual axis identification system includes a fixation light source, a camera, and a processing system. During its operation, a patient focuses their gaze onto two or more fixation spots provided by the fixation light source, where the two or more fixation spots produce two or more corresponding images on or near the patient's retina. The patient's head is then rotated (with reference to Figure 14B described in more detail). When the centers of the multiple images coincide within the patient's field of view, the patient's visual axis can be located by determining the position of the optical axis of the fixation light source relative to the patient's eye.

[0034] Figure 1 A schematic cross-sectional top view of an exemplary human eye 100 is shown. In Figure 1 temporal and nasal sides of the eye 100 are depicted for reference. As depicted, the pupillary axis 102 passes through the pupillary center 104 of the pupil 106 and is perpendicular to the pupil plane 108. The eye 100 further includes a visual axis 110 that intersects the pupil 106 at a visual axis point 112. The visual axis 110 connects a fixation point 114 (e.g., a fixation target) with a fovea 122, which is a small pit in the retina 116. The center of the field of view is focused on the fovea 122, so the clearest vision of a target is obtained when the target is in line with the fixation point 114 and the fovea 122. Thus, accurate determination of the visual axis point 112 is essential for successful ophthalmic corrective surgery. However, as previously mentioned, there are currently no ophthalmic diagnostic devices that can accurately and precisely identify the visual axis point 112. Rather, conventional ophthalmic techniques involve approximating the visual axis point 112 as being midway between the pupillary center 104 and the corneal vertex 118 or the first Purkinje image, which is defined as the specular reflection position of the corneal anterior surface, as seen from the direction of the fixation light source.

[0035] Figure 2 A front view of the eye 100 as seen by a clinician (e.g., an ophthalmologist) during a procedure is shown. In Figure 2 the visual axis point 112 is assumed to be midway between the pupillary center 104 and the corneal vertex 118. However, the visual axis point 112 is often not midway between the pupillary center 104 and the corneal vertex 118, particularly in asymmetric, irregular, or damaged eyes. Thus, the approximation of the location of the visual axis point 112 can be inaccurate, imprecise, and unreliable, and can result in suboptimal presbyopic Lasik or PRK treatment.

[0036] Figure 3A simplified schematic of an exemplary visual axis identification system 300 is shown in accordance with some embodiments. The visual axis identification system 300 is used to accurately and precisely determine a visual axis point 112 of a visual axis 110 of an eye 100. Generally, the visual axis identification system 300 includes a fixation light source 302, a camera 304, and a processing system 306.

[0037] The fixation light source 302 is configured to form two or more fixation spots P N ( e.g., Figure 4A and Figure 4B shown in FIGS. 1-3), on which a patient's eye (represented by the eye 100) can focus during use of the visual axis identification system 300. In operation, the patient focuses on the two or more fixation spots P N and attempts to visually align the fixation spots by moving his or her head. When the visual axis 110 of the eye 100 and the optical axis 312 of the fixation light source 302 coincide, alignment or overlap of the fixation spots P N is achieved. Thus, at alignment, the visual axis point 112 can be identified. To produce light, the fixation light source 302 can include any suitable light emitting device, including a light emitting diode (LED), an incandescent lamp, etc. In certain embodiments, the produced light is concentrated by a multiplexer 320 into the two or more fixation spots P N and then relayed by a relay lens 322 along the optical axis 312.

[0038] In certain embodiments, the visual axis identification system 300 further includes an optical relay device 310 along the optical axis 312 for relaying the fixation spots P N to the eye 100 and / or manipulating the propagation path of the optical axis 312. For example, the optical relay device 310 can be used to align the optical axis 312 of the fixation light source 302 with an optical axis 314 of the camera 304. Examples of suitable types of optical relay devices include relay lenses, beam splitters, optical filters, etc. While one optical relay device 310 is depicted, it is also contemplated to utilize two or more optical relay devices 310.

[0039] The camera 304 can include any suitable type of digital imaging device or detector, such as an eye tracking camera or similar optical sensor, for capturing images of the eye 100 and determining the position (e.g., X / Y translational position) of the eye. Generally, the camera 304 is configured for recording when the patient is focusing on the fixation spots P NAn image or video of the iris plane of the eye 100 is generated. The image or video is then transmitted to the processing system 306 for analysis to determine the relative X / Y position of the eye 100 and its visual axis point 112. In some embodiments, the camera 304 is an infrared camera. In some embodiments, the camera 304 is configured to track the movement of the eye 100, particularly the pupil center 104, by mapping and detecting deviations (e.g., movements) of the vascular system (e.g., blood vessels) within the eye 100 (e.g., scleral veins). The camera 304 is communicatively coupled to the processing system 306 and, in some embodiments, forms a single device with it. In some other embodiments, the camera 304 and the processing system 306 may be separate devices or components of the visual axis recognition system 300.

[0040] To demonstrate example operation of the visual axis recognition system 300, Figures 4A-4B and Figures 5A-5B A simplified schematic diagram depicts the eye 100 focusing on two fixed light spots P1 and P0. Figure 4A and Figure 5A The image formation in the eye 100 is schematically illustrated by fixation spots P1 and P0, while Figure 4B and 5B The corresponding images C1 and C0 formed on the retina 116 are shown. Imaging system 120 represents the image-forming components of the eye, such as the cornea with a typical refractive power of about 43 diopters and the natural lens with a typical refractive power of about 17 diopters. As described above, fixation light source 302 is configured to generate light and concentrate it into at least two fixation spots P1 and P0 aligned on its optical axis 312. Figure 4A In the example shown, fixation spot P0 is imaged onto retina 116, while fixation spot P1 is imaged near retina 116 (e.g., slightly in front). This makes image C0 appear small and sharp to the patient, while image C1 appears larger and less sharp (e.g., more blurred) compared to image C0.

[0041] like Figure 4A and 4B The depiction shows the optical axis 312 of the fixed light source 302. Figure 3 When the images C1 and C0 coincide with the visual axis 110 of the patient's eye 100 (as shown), the centers of images C1 and C0 coincide on the retina 116. Therefore, the patient sees a small, clear image C0 that is centered or overlaps with the large, blurry image C1. Figure 4B As shown. However, as Figure 5A and Figure 5B As depicted, when the optical axis 312 and the visual axis 110 are not aligned, images C1 and C0 are spatially offset relative to each other. Therefore, the patient can see both C1 and C0, even though their centers are not aligned or coincident, as... Figure 5BThe principle is then utilized, in certain embodiments, to identify the location of the visual axis point 112 by having the patient move or adjust their head up and down or side to side while maintaining their gaze on the fixation spots Pi and Po until the patient sees the images Ci and Co centered or overlapping, thereby indicating that the visual axis 110 is aligned with the optical axis 312 of the fixation light source 302. See Figure 14B A more detailed description of patient head movement is obtained below.

[0042] Figure 6A and Figure 6B A simplified schematic of a multiplexer 320 and relay lens 322 of a fixation light source 302 forming two or more fixation spots according to certain embodiments of the present disclosure is shown. As previously described, during operation of the visual axis identification system 300, the patient observes the fixation spots produced by the multiplexer 320 through the use of the relay lens 322. As further described above, the visual alignment of the fixation spots can be utilized to locate the patient's visual axis point 112. While Figure 6A and Figure 6B is a demonstration of the functionality of the multiplexer 320, a more detailed description of specific examples or types of multiplexers is obtained below. Figures 7-13B

[0043] In Figure 6A , the multiplexer 320 is a spot multiplier and concentrates the incoming light 602 into two fixation spots Pi and Po on the optical axis 312. In Figure 6B , the multiplexer 320 is a spot multiplexer and concentrates the incoming light 602 into three fixation spots P2, Pi, and Po. While only three fixation spots are shown in Figure 6B , it is contemplated that the multiplexer 320 can produce more than three fixation spots. In certain embodiments, increasing the number of fixation spots improves the accuracy of the visual identification system 300. In either of the depicted examples, the patient observes the fixation spots produced by the multiplexer 320 through the relay lens 322, which serves at least two functional purposes: first, the relay lens 322 relays the fixation spots to the eye 100 (e.g., similar to a magnifying glass); second, the relay lens 322 compensates for the refractive error of the eye 100 so that the fixation spots appear clear to the patient (e.g., acting as a Badal system).

[0044] As previously described, Figures 7-13B A specific example of a multiplexer 320 that can be used to concentrate light within a fixation light source 302 into two or more fixation spots on its optical axis (e.g., optical axis 312) is shown. The patient observes the fixation spots formed by the multiplexer 320 and attempts to align these fixation spots to assist the visual axis identification system 300 in identifying the visual axis point 112.​

[0045] In Figure 7 the depicted example, multiplexer 320 is a bifocal lens 720 having two foci F0and Fi, at which light 602 is concentrated. Concentration of light 602 at the two foci F0and Fi causes two fixation spots to be produced on optical axis 312, which are relayed toward the patient's eye, as seen in Figure 4A depicted. In Figure 8 another depicted example, multiplexer 320 is a multifocal diffractive lens 820. Multifocal diffractive lens 820 includes one or more features 822 or properties configured to focus light 602 at multiple foci at different diffraction orders on optical axis 312. As Figure 8 depicted, multifocal diffractive lens 820 focuses light 602 at five different foci, including a zeroth order focus F0and higher order foci Fi, F2, F -1 , and F -2 . Each focus F0, Fi, F2, F -1 , and F -2 corresponds to a fixation spot that the patient can observe. While five foci are shown, it is contemplated that multifocal diffractive lens 820 can form fewer than five or more than five foci. In certain embodiments, multifocal diffractive lens 820 is a Fresnel type lens. In certain other embodiments, multifocal diffractive lens 820 is a holographic lens or diffractive optical element formed by holographic or lithographic techniques.

[0046] Figure 9 Another example of a multiplexer 320 that can be used in fixation light source 302 is shown. Figure 9 In the depicted example, multiplexer 320 in fixation light source 302 is a lens 902 having a coating 904 on both major surfaces 906. Coating 904 is partially reflective and partially transparent, and thus, light 602 is reflected by coating 904 and also transmitted therethrough to form multiple foci. When the incident beam of light rays 602 is parallel to and centered on optical axis 312, the multiple foci formed by lens 902 coincide with optical axis 312. As depicted, focus F0is the focus resulting from the condition of light 602 being transmitted through lens 902 without any internal reflections thereof. However, focus Fi is produced by two internal reflections by coating 904. Foci F2and F3are produced by four and six internal reflections, respectively. Because at least one of major surfaces 906 is curved, different reflection angles and / or reflection powers are produced, and thus, foci F0, Fi, F2, and F3are formed at different locations on optical axis 312.

[0047] In certain embodiments, the coating 904 enables spectral separation of the light 602. For example, a reflectivity peak (e.g., a maximum reflectivity) of the coating 904 can correspond to a wavelength of the light 602 that the patient will see. In another example, the coating 904 has zero reflectivity at the wavelength of the light 602 when detected by the camera 304. Thus, unwanted reflections of the light 602 toward the camera 304 can be eliminated or substantially reduced by the coating 904.

[0048] In Figure 10 the example multiplexer 320 is a Fabry-Perot interferometer (FPI) 1020 having two parallel and semi-transparent (e.g., partially reflective) mirrors 1004 in combination with a focusing convex lens 1010. The focusing convex lens 1010 focuses the parallel light 602 beam onto the FPI 1020, which then internally reflects and / or transmits the light to form several foci on the optical axis 312. In Figure 10 four foci F0, Fl, F2, and F3 are depicted, but more or fewer foci are contemplated. The first focus F0 is the result of the light 602 passing through the FPI 1020 without any internal reflections. However, the foci Fl, F2, and F3 are the result of two, four, and six internal reflections, respectively.

[0049] In Figure 11 another example depicted, the multiplexer 320 is an interferometer 1120. In particular, Figure 11 a Michelson-type interferometer 1120 having two peripheral total reflecting mirrors 1114A and 1114B and one semi-transparent (e.g., partially reflective) central mirror 1112 is depicted. Each peripheral mirror 1114A and 1114B is disposed at a different distance (e.g., arm length) from the central mirror 1112. As shown, the central mirror 1112 reflects a portion of the incident light 602 to the peripheral mirror 1114A and transmits another portion of the light 602 to the peripheral mirror 1114B. After being reflected by the mirrors 1114A and 1114B, the light 602 is again reflected or transmitted by the central mirror 1112 disposed along the optical axis 312. The different arm lengths of the peripheral mirrors 1114A and 1114B cause the light 602 reflected from each mirror to be focused at different foci (depicted as foci F A and F B ) along the optical axis 312. In certain embodiments, the interferometer 1120 is optically coupled with a focusing convex lens 1110 to focus the light 602 onto the central mirror 1112. Furthermore, while the interferometer 1120 is depicted as a Michelson-type interferometer, any suitable type of interferometer can be used as the multiplexer 320. For example, in certain embodiments, the interferometer 1120 can be a Mach-Zehnder, Twyman-Green, or Gires-Tournois interferometer.

[0050] Figure 12 、 Figure 13A and Figure 13B An example of a multiplexer 320 configured to produce a Bessel beam (e.g., a non-diffracting beam) is shown. A Bessel beam has an extremely long focal line, which can be interpreted as many multiplexed focal points whose foci overlap in depth. In operation, a patient observes the fixation spot formed by the Bessel beam and rotates their head to align the Bessel beam with their visual axis 110, causing the Bessel beam to appear as a single spot. Upon visualizing the Bessel beam as a single spot, the patient’s visual axis point 112 can be located.

[0051] In the example of Figure 12 , the multiplexer 320 is an axicon prism 1220 having at least one conical refractive surface 1206. The conical surface 1206 has rotational symmetry about the optical axis 312, thus refracting the light 602 into an intersecting beam (e.g., a Bessel beam) that forms a very long focal line F L on the optical axis 312.

[0052] In another example of a Bessel beam generator, Figure 13A and Figure 13B depict front and side view illustrations of an annular ring (e.g., an annular aperture) 1320 formed in a screen 1322. When the annular ring 1320 is axially aligned with a focusing convex lens 1310, the light 602 passes through the annular ring 1320 and is focused by the convex focusing lens 1310 to form a focal line F L on the optical axis 312, similar to the axicon prism 1220. In yet further examples, the multiplexer 320 can also include diffractive or holographic optical elements configured to produce a Bessel beam.

[0053] As described above, Figures 7-13B different multiplexers shown can be used in a visual axis identification system, such as the visual axis identification system 300 of Figure 3 . Figure 14A and 14B illustrate a slightly simplified version of the visual axis identification system 300 of Figure 3 , and the example operation of the visual axis identification system 300 is described in more detail herein with respect to Figure 14A and Figure 14B . As depicted, the fixation spots P0-P4 pass through the multiplexer 320 of the fixation light source 302 (e.g., which can be the Figures 7-13B) to the optical axis 312. By utilizing one or more optical relay devices 310 to direct the optical axis 312 toward the patient’s eye 100. As the patient successively fixes his or her gaze on the fixation light spots P0-P4, the patient makes a “yes” movement (e.g., rotation about the Y-axis) and / or a “no” movement (e.g., rotation about the X-axis) of his or her head until the fixation light spots P0-P4 appear to be centered coincident or aligned. When the corresponding images C0-C4 of the fixation light spots P0-P4 (as shown in Figure 15A and Figure 15B the optical axis 312 is aligned with the visual axis 110 of the patient’s eye 100.

[0054] Figure 14B A “no” movement of the head is also depicted as to how the eye 100 deviates along a lateral direction or plane. For example, if the distance D between the cornea and the vertical anatomical axis of rotation X of the head is 80 mm, then a 1° rotation of the head about the vertical axis of rotation X (i.e., a “no” movement) will cause the eye 100 to deviate along a lateral direction by 80 mm * sin(l°) = 1.4 mm.

[0055] Simultaneous with the rotational movement of the patient’s head, the camera 304 captures images or video of the iris plane of the eye 100 from the direction of light propagation from the fixation light source 302 to the eye 100. In certain embodiments, the optical axis 314 of the camera 304 is aligned with the optical axis 312 of the fixation light source 302, and thus is also aligned with the visual axis 110 of the patient’s eye 100 when the patient observes the centered coincident or aligned images C0-C4 of the fixation light spots P0-P4. Thus, at the point at which the patient observes the coincident images C0-C4 of the fixation light spots P0-P4, the optical center of the camera 304 (whose optical axis 314 is aligned with the optical axis 312 of the fixation light source 302) corresponds to the visual axis point 112 of the eye 100. In certain embodiments, the optical center of the camera 304 is marked on the captured images or video, or on a display screen observed by a user (e.g., a surgeon).

[0056] Once the patient achieves alignment of the fixation light spots P0-P4, the patient maintains his or her position to maintain this alignment while the camera 304 captures images of the eye 100 to locate the visual axis point 112 corresponding to the optical center of the camera 304. In certain embodiments, while the patient maintains alignment of the images C0-C4 of the fixation light spots P0-P4, the camera 304 captures video or a series of images over a desired amount of time. In certain embodiments, the processing system 306 (e.g., a computer) processes the captured images or video to locate the visual axis point 112 corresponding to the optical center of the camera 304. Figure 14A and Figure 14BThe average X / Y position of the optical center of the camera 304 relative to the average X / Y position of the eye 100 is determined by analyzing the video (which comprises a series of images) or series of images captured by the camera 304 (not shown) to account for any accidental movement of the patient's eye and / or head on average when viewing the fixation spots P0-P4. The average X / Y position of the optical center of the camera 304 corresponds to the point of the visual axis 112 of the eye 100. The determined average X / Y position of the optical center of the camera 304 relative to the X / Y position of the eye 100 corresponds to the average of all X / Y positions of the optical center of the camera 304 in this series of images, see below Figure 16 Further details are described in further detail.

[0057] Figure 15A and Figure 15B A schematic view of the multiple fixation spots P0-P4 produced by the multiplexer 320 in the eye 100 viewing through the Figure 14A and 14B As shown in Figure 15A When all fixation spots P0-P4 are aligned with the visual axis 110 of the patient's eye 100, the fixation spots P0-P4 form coinciding images Cl-C4 on the retina 116. The patient can achieve this alignment by making a "yes" or "no" movement of his or her head around the X and / or Y axis while continuously maintaining focus on the fixation spots P0-P4, as described above and shown in Figure 14B After alignment, the patient tries to keep their position so that the camera 304 can capture images or video of the position of the eye 100 relative to the optical center of the camera 304. When the fixation spots P0-P4 (and the optical axis 312) are not aligned with the visual axis 110, as shown in Figure 15B the fixation spots P0-P4 form spatially offset images Co-C4 on the retina 116 and the patient has to adjust his or her head position.

[0058] Figure 16 A front view image of the eye 100 during use of the visual axis identification system according to certain embodiments of the present disclosure using Figure 3 and Figures 14A-14B is shown. Figure 16The depicted view can be the view of the camera 304, which can be displayed on a display screen for the surgeon to view. As shown, the trajectory 1610 shows the history of the position of the optical axis 312 of the fixation light source 302 on the iris plane of the eye 100, and the landmark 1610 represents the center of gravity of the trajectory 1620. During operation, the optical center of the camera 304 is configured to coincide with the optical axis 312 of the fixation light source 302. The position of the optical center (and thus the optical axis 312) of the camera 304 is tracked by the trajectory 1620 in the images or video captured when the patient observes the center-aligned fixation spot. This trajectory 1620 is then analyzed to determine the X / Y position of the landmark 1610, which indicates the center of gravity of the trajectory 1620 relative to the X / Y position of the eye 100, which corresponds to the “average” point of the visual axis 112. In certain embodiments, the relative X / Y positioning of the landmark 1610 to the eye 100 is determined by mapping and tracking of the scleral veins 1602.

[0059] Figures 17A-17D A representation of the field of view of the patient when observing the fixation spot P N formed by the fixation light source 302 is shown. As Figures 17A-17C shown, when the optical axis 312 and the visual axis 110 are misaligned, the patient sees the fixation spot P N in both size and clarity. However, when the axes 312 and 110 are aligned, the fixation spot spatially coincides or overlaps, as Figure 17D shown. Figure 17E A system 1700 for obtaining the above representation is shown. The system includes a point-like fixation light source 1702 for producing fixation light, a coating lens 1722 for focusing the fixation light into two or more fixation spots, and a camera 1704 for capturing images of the fixation spots focused by the coating lens 1722. When the optical center 1706 of the camera 1704, the optical center 1724 of the coating lens 1722, and the optical axis 1712 of the fixation light source 1702 coincide, the camera 1704 captures images similar to Figure 17D When the optical center 1724 of the coating lens 1722 is spatially (e.g., in the X or Y direction) offset relative to the optical axis 1712 and / or the optical center 1706 of the camera 1704, the camera 1704 captures images similar to Figures 17A-17C When the optical center 1724 of the coating lens 1722 is spatially (e.g., in the X or Y direction) offset relative to the optical axis 1712 and / or the optical center 1706 of the camera 1704, the camera 1704 captures images similar to

[0060] Figure 18A simplified schematic diagram of an alternative visual axis recognition system 1800 according to certain embodiments of the present disclosure is shown. As depicted, the visual axis recognition system 1800 is substantially similar to the visual axis recognition system 300, but includes an additional camera 1804, which can be used with the processing system 306 ( Figure 3 (As shown) and / or camera 304 are operatively coupled to trigger image capture by camera 304. Camera 1804 is focused on the retina of eye 100 and can therefore be a fundus camera. In some embodiments, camera 1804 monitors or examines the retina to understand the formation of an image, such as images CO-C4, on the retina corresponding to the fixation spot generated by fixation light source 302. When images CO-C4 overlap on the retina, camera 1804 can recognize the overlap event and trigger camera 304 (e.g., by direct communication with camera 304 or by processing system 306) to record or capture an image of the iris plane of eye 100. As described above, when images CO-C4 overlap on the retina, visual axis 110 is aligned with optical axis 312 and also coincides with the optical center of camera 304. Therefore, image capture by camera 304 can be automatically triggered by camera 1804 when the optical center of camera 304 is aligned with visual axis 110, thereby eliminating or reducing inaccuracies caused by the patient's limited cooperative skills.

[0061] Figure 19 A flowchart illustrating a method 1900 for determining the position of visual axis point 112 using visual axis recognition systems 300 and 1800, according to certain embodiments of the present disclosure, is shown. Typically, in operation 1910, when using visual axis recognition systems 300 or 1800, the patient focuses their gaze on a fixation spot generated by fixation light source 302. These fixation spots are focused on the optical axis 312 of fixation light source 302 and relayed toward the eye of patient 100. In operation 1920, a camera 304, with its optical axis 314 aligned with the optical axis 312 of fixation light source 302, is focused on the iris plane of the patient's eye 100. In some embodiments, the optical center of camera 304 and the corresponding optical axis 314 are marked within the field of view of camera 304.

[0062] In operation 1930, the patient is asked to rotate his or her head while continuously maintaining their gaze on the fixation light spot until the center of the fixation light spot is aligned within the patient's field of view. The patient can move or rotate their head in either the X or Y rotational direction to align the center of the fixation light spot within their field of view. While the patient's head is moving, the camera 304 captures images or video of the eye 100 while tracking its X / Y position relative to the X / Y position of the optical axis 314. In certain embodiments, the tracking of the relative X / Y position of the eye 100 is performed using features of the sclera, such as the blood vessels of the scleral veins described above. In certain embodiments, during a "test" or "trial" period in which the camera 304 does not capture images of the eye 100, the patient is asked to rotate his or head to align the fixation light spot. For example, the patient can be asked to practice this movement during a trial period of about 30 seconds, after which the "measurement" period begins and the camera 304 begins capturing images or video.

[0063] In certain embodiments, in operation 1940, the center of the fixation light spot is aligned and the patient is asked to maintain the aligned nature or state of the fixation light spot while the camera 304 continues to capture images or video of the patient's eye 100. For example, the patient maintains the aligned state of the fixation light spot for a desired period of time, such as about 30 seconds, while the camera 304 continuously or intermittently records the X / Y position of the eye 100 and relays the images to the processing system 306. Then, in operation 1950, the processing system 306 can analyze the series of video or images to determine the average X / Y position of the X / Y position of the optical axis 314 relative to the eye 100, thereby compensating for any inadvertent movement of the patient's eye and / or head. Accordingly, the identification of the average X / Y position of the optical axis 314 corresponds to the approximate X / Y position of the visual axis point 112.

[0064] In certain other embodiments, in operation 1940, the second camera 1804 monitors the retina of the patient's eye 100 and automatically triggers the camera 304 to capture images of the eye 100 when the corresponding image of the fixation light spot on the retina is aligned. The use of the second camera 1804 enables automatic image capture of the eye 100 when the optical axis 314 is aligned with the visual axis 110, thereby eliminating or greatly reducing any inaccuracies caused by inadvertent movement of the patient's eye and / or head and patients with limited coordination skills. After the camera 304 captures the images, in operation 1950, the processing system 306 analyzes the images to determine the X / Y position of the visual axis point 112.

[0065] The above-described methods and devices provide a novel visual axis identification system that can be used to improve the efficacy of ophthalmic procedures, such as presbyopia treatment (including the fitting of corrective lenses, refractive surgery, intraocular lens implantation, and multifocal corneal inlays). The described visual axis identification system can further be used in conjunction with any suitable ophthalmic diagnostic device. Examples of suitable diagnostic devices include corneal topographers, optical coherence tomographs, wavefront instruments (e.g., aberrometers), image-guided biometers, surgical microscopes, and other image-based diagnostic devices. In some examples, the visual axis identification systems 300 and 1800 can be used in conjunction with the Verion® System, LuxOR® LX3 platform, manufactured by Alcon, Fort Worth, Texas. In some examples, the visual axis identification systems 300 and 1800 can be used with ophthalmic platforms provided by other manufacturers. TM 、 ORA TM System、 LuxOR TM LX3 platform. In some examples, the visual axis identification systems 300 and 1800 can be used with ophthalmic platforms provided by other manufacturers.

[0066] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure can be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A method for determining a point of regard location of a patient's eye, comprising: directing a fixation light to the patient's eye with a fixation light source, the fixation light comprising two or more fixation light spots formed at different positions along an optical axis of the fixation light source and corresponding to two or more images formed on or near a retina of the patient's eye; monitoring by a retinal monitoring camera focused on the retina of the patient's eye and producing an indication when centers of the two or more images are identified to coincide; receiving, in an image capture camera, the indication of the centers of the images coinciding from the retinal monitoring camera, whereby the image capture camera is automatically triggered to capture one or more digital images of an iris plane of the patient's eye when the centers of the two or more images formed on or near the retina coincide within the patient's field of view and simultaneously when an optical center of the image capture camera is aligned with the optical axis on which the fixation light spots are formed; and identifying a point of regard location at the iris plane based on the one or more digital images, the point of regard location corresponding to an X / Y location of the optical center of the image capture camera relative to an X / Y location of the patient's eye shown in the one or more digital images.

2. The method of claim 1, wherein, The point of regard location further corresponds to an X / Y location of the optical axis of the fixation light source at the iris plane when the centers of the images coincide within the patient's field of view.

3. The method of claim 1, wherein: the one or more digital images comprise a plurality of images; and identifying the point of regard location of the patient's eye further comprises spatially averaging an X / Y location of the optical center of the image capture camera relative to an X / Y location of the patient's eye shown in the corresponding plurality of digital images.

4. The method of claim 3, wherein, The plurality of images are captured over a time period of about 30 seconds.

5. The method of claim 1, further comprising: determining the X / Y location of the patient's eye by mapping and tracking a vasculature within a sclera of the patient's eye.

6. The method of claim 1, wherein, triggering capture of the one or more digital images by a user after receiving the indication of the centers of the images coinciding from the patient and receiving the indication of the centers of the images coinciding in the image capture camera from the retinal monitoring camera.

7. A system for determining a point of regard location of a patient's eye, comprising: a fixation light source configured to produce two or more fixation light spots at different positions along an optical axis and corresponding to two or more images formed on or near a retina of the patient's eye; a retinal monitoring camera focused on the retina of the patient's eye, wherein the retinal monitoring camera monitors the retina and produces an indication when centers of the two or more images are identified to coincide; an image capture camera configured to receive the indication of the centers of the images coinciding from the retinal monitoring camera, whereby the image capture camera is automatically triggered to capture one or more digital images of an iris plane of the patient's eye when the centers of the two or more images formed on or near the retina coincide within the patient's field of view and simultaneously when an optical center of the image capture camera is aligned with the optical axis on which the fixation light spots are formed. an image capture camera configured to capture digital images of the iris plane of the patient's eye when an optical center of the image capture camera is aligned with an optical axis on which the fixation light spots are produced, and to track the X / Y position of the patient's eye, and configured to receive an indication of a center coincidence of the image from the retinal monitoring camera, thereby automatically triggering the image capture camera to capture one or more digital images of the iris plane of the patient's eye; and a processing system configured to identify a point of regard location at the iris plane based on the one or more digital images captured by the image capture camera, wherein the point of regard of the eye corresponds to an X / Y position of an optical center of the image capture camera relative to the X / Y position of the patient's eye when centers of images formed by the two or more fixation light spots on the retina of the patient's eye coincide within the patient's field of view.

8. The system of claim 7, wherein, The processing system configured to identify the point of regard location of the patient's eye includes a processing system configured to: average the X / Y position of the optical center of the image capture camera relative to the X / Y position of the patient during a period of time when the patient maintains their gaze on the fixation light spots such that the patient observes the center coincidence of the image.

9. The system of claim 7, wherein, The image capture camera is configured to map and track vasculature within the sclera of the patient's eye to determine the X / Y position of the patient's eye.

10. The system of claim 7, wherein, The image capture camera is an infrared camera.

11. The system of claim 7, wherein, The fixation light source further includes a multiplexer configured to produce the two or more fixation light spots from incident light, and wherein the multiplexer is one of a bifocal lens, a multifocal diffractive lens, a coated lens, a Fabry-Perot type system, a non-diffractive Bessel beam generator, or an interferometer. The processing system configured to identify the point of regard location of the patient's eye includes a processing system configured to: average the X / Y position of the optical center of the image capture camera relative to the X / Y position of the patient during a period of time when the patient maintains their gaze on the fixation light spots such that the patient observes the center coincidence of the image. The image capture camera is configured to map and track vasculature within the sclera of the patient's eye to determine the X / Y position of the patient's eye. The image capture camera is an infrared camera. The fixation light source further includes a multiplexer configured to produce the two or more fixation light spots from incident light, and wherein the multiplexer is one of a bifocal lens, a multifocal diffractive lens, a coated lens, a Fabry-Perot type system, a non-diffractive Bessel beam generator, or an interferometer.

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