Human Visual Axis Identification System and Method

Abstract

The present disclosure generally relates to a method and apparatus for accurately identifying the visual axis of an eye. In one embodiment, the visual axis identification system includes a fixation light source, a camera, a processing system, and a multifocal lens. A patient gazes through the multifocal lens onto a fixation light beam provided by the fixation light source. As the fixation light beam passes through the multifocal lens, two or more images are created on or near the patient's retina. The multifocal lens and / or the patient's eye then move relative to one another while the patient continuously maintains gaze on the fixation light beam. The patient's visual axis can be located by locating the optical center of the multifocal ophthalmic lens relative to the patient's eye when the centers of the multifocal images coincide on the retina.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to methods and apparatuses for characterizing vision, and more particularly to methods and apparatuses for accurately identifying the visual axis of an eye.

Background Art

[0002] Conventional techniques for the treatment of presbyopia typically involve identifying the relative locations of the visual axes of each eye of a patient. Accurate identification of these axes is extremely important for the effective placement of small area bifocal, multifocal, and extended depth of focus (EDOF) intraocular lenses (IOLs). Even a slight misalignment of these axes can significantly compromise any benefits intended by their surgical implantation. Also, to name a few other examples of presbyopia treatments that can benefit from the identification of the visual axis, there are LASIK, presbyLASIK, or multifocal LASIK, and photorefractive keratectomy (PRK) surgery.

[0003] The visual axis is an actual line of sight that is a small depression in the retina and converges on the fovea centralis of the eye, which is the clearest point of view when the fixation point is in the patient's field of view. Therefore, the measurement of the visual axis is extremely important for determining the placement of bifocal and multilayer point lenses, because the viewing areas of such lenses are narrow and even a slight misalignment can significantly compromise their functions. Currently, there is no diagnostic device that can accurately and precisely identify the location of the visual axis. Instead, the location of the visual axis is generally approximated as the midpoint between the optical axis and the first Purkinje image, which is the reflection of the fixation light on the corneal apex or the outer corneal surface. This method is often inaccurate because the visual axis may be located far from the above midpoint (for example, especially in damaged eyes or eyes with an abnormal shape).

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, there is a need in the art for improvements in methods and apparatuses for identifying the visual axis of an eye.

Means for Solving the Problem

[0005] The present disclosure generally relates to methods and apparatuses for accurately identifying the visual axis of an eye.

[0006] In certain embodiments, a method for determining the location of the visual axis of a patient's eye is provided. The method includes placing a multifocal optical lens adjacent to the patient's eye, the multifocal optical lens including two or more refractive powers having corresponding spatially coincident optical centers at the optical center of the multifocal optical lens. A fixation light beam is generated and directed towards the patient's eye, the fixation light beam forming two or more images corresponding to the two or more refractive powers of the multifocal lens near the patient's retina. The method further includes capturing an image of the patient's eye and the optical lens along the direction of the fixation light beam and determining the X / Y location of the patient's eye relative to the X / Y location of the optical center of the multifocal optical lens. The multifocal optical lens moves along the X / Y direction while the patient maintains fixation on the fixation light until the centers of the two or more images coincide in the patient's view. At that point, the location of the visual axis of the patient's eye is detected and located on the pupil plane of the patient's eye, and the location of the visual axis corresponds to the location of the optical center of the multifocal optical lens as viewed from the direction of the fixation light beam.

[0007] To better understand the features of the present disclosure enumerated above, a more detailed description of the present disclosure, briefly summarized above, can be obtained by referring to the embodiments, some of which are shown in the accompanying drawings. However, it should be noted that the accompanying drawings merely illustrate exemplary embodiments and should not be considered as limiting the scope, as other equally effective embodiments may be recognized.

Brief Description of the Drawings

[0008]

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[0009] For ease of understanding, where possible, the same reference numerals are used to denote the same elements common to multiple figures. It is contemplated that the elements and features of one embodiment may be beneficially incorporated into other embodiments without further recitation.

[0010] The present disclosure generally relates to methods and apparatuses for accurately identifying the visual axis of an eye. In certain embodiments, the visual axis identification system includes a fixation light source, a camera, a processing system, and a multifocal lens. The multifocal lens may be coupled to an ophthalmic frame worn by a patient or an extraocular device. In determining the location of the patient's visual axis, the patient gazes through the multifocal lens at a fixation light beam provided by the fixation light source. When the fixation light beam passes through the multifocal lens, two or more images are created on or near the patient's retina. While the patient maintains continuous fixation on the fixation light beam, the multifocal lens and / or the patient's eye are then moved relative to each other. The patient's visual axis may be located by identifying the location of the optical center of the multifocal ophthalmic lens relative to the patient's eye when the centers of the multifocal images coincide on the retina.

[0011] FIG. 1 shows a simplified cross-sectional top view of an exemplary human eye 100. The temple side and nasal side of the eye 100 are shown in FIG. 1 for reference. Generally, the eye 100 includes a cornea 104, a pupil with center 106 shown, an iris 108, a natural lens 110, ciliary muscle 112, and a retina 116. The pupil axis 118 is orthogonal to the plane of the iris 108 and passes through the pupil center 106.

[0012] FIG. 1 shows the fixation point P 1Further shown is the visual axis 120 through the cornea 104 and the pupil to the fovea 122, which is referred to as a small depression in the retina 116. The center of the visual field is imaged at the fovea 122, where the cones are particularly concentrated, and thus the visual acuity is highest along the visual axis 120. Therefore, the accurate identification of the location 130 of the visual axis 120 is extremely important for the successful alignment of bifocal or multifocal corrective lenses. The location 130 of the visual axis 120 refers to the X / Y position or location of a point on the plane of the iris 108 through which the visual axis 120 passes or on the pupil plane. However, as described above, currently, there is no ophthalmic diagnostic device that can precisely identify the location 130 of the visual axis 120.

[0013] Conventional ophthalmic techniques involve approximating the location 130 of the visual axis 120 as the midpoint between the pupil center 106 and the first Purkinje image defined as the location of the specular reflection from the front surface of the cornea 104 as viewed from the direction of the corneal apex 132 or the fixation light source. Current approximation techniques may lead to misalignment of multifocal corrective lenses or ineffective or suboptimal corrective treatments such as presbyopia or PRK treatment. Embodiments of the present disclosure provide improvements to systems and methods for accurately locating the intersection (location 130) of the visual axis 120 and the pupil plane of the eye. Therefore, embodiments of the present disclosure can be utilized in the alignment of corrective lenses and other ophthalmic procedures including ophthalmic surgeries such as multifocal LASIK or multifocal PRK surgery.

[0014] Figure 2 shows a simplified schematic diagram of an exemplary visual axis identification system 200 according to some embodiments. The visual axis identification system 200 includes a fixation light source 202, an imaging camera 204, an image processing system 206, and a multi-focus lens 208. Generally, the fixation light source 202 and one or more associated optical relay devices 210 are configured to provide a fixation light beam 212 to the eye 100. For example, the fixation light source 202 may include one or more light emitting diodes (LEDs) configured to emit the fixation light beam 212. Other examples of suitable light sources that may be utilized for the fixation light source 202 include incandescent bulbs and the like. In some embodiments, the fixation light source 202 may provide a fixation light beam 212 having multiple wavelengths. The one or more optical relay devices 210 may include any suitable optical relay devices such as relay lenses, beam splitters, filters, and the like.

[0015] The imaging camera 204 may include any suitable digital imaging device or image detector such as an eye tracking camera or a similar optical sensor that captures images of the eye 100 and the multi-focus lens 208 and identifies their locations (e.g., X / Y translation positions). In some embodiments, the imaging camera 204 is an infrared optical sensor configured to track the X / Y location of the eye 100 and the X / Y location of the multi-focus lens 208. In such embodiments, the eye 100 is illuminated by the infrared fixation light source 202. In some embodiments, the imaging camera 204 is an optical sensor configured to track the movement of the eye 100 by mapping and detecting a shift (e.g., movement) of blood vessels or the like within the eye 100, such as blood vessels within the sclera, which is the white outer layer of the eye 100.

[0016] The imaging camera 204 is communicatively coupled to the image processing system 206 and may form a single device with the image processing system 206. For example, the imaging camera 204 and the image processing system 206 may be separate components within a single imaging device or system. Generally, the imaging camera 204 is configured to capture images of the eye 100 and transmit those images to the image processing system 206 for analysis during use of the visual axis identification system 200. The image processing system 206 is then configured to identify the X / Y location of the eye 100 and the X / Y location of the multifocal lens 208.

[0017] The identification of the X / Y location of the eye 100 by the image processing system 206 is performed relative to the X / Y location of the multifocal lens 208. The multifocal lens 208 can be any suitable type of multifocal optical lens. In certain embodiments, the multifocal lens 208 is a multifocal lens having two or more refractive powers, such as a bifocal lens. In certain embodiments, the multifocal lens 208 is a multifocal lens having reflective coatings on two or more sides. In further embodiments, the multifocal lens 208 includes diffractive optical elements such as holographic elements, Fresnel type lenses, etc. In further embodiments, the multifocal lens 208 includes an axicon or an aspherical extended depth of focus lens that forms a long or super-long focal line (i.e., a Bessel beam) instead of a single focus. Super-long focal line F L An exemplary axicon 218 that forms the super-long focal line is shown in FIG. 2B. Also note that although the multifocal lens 208 is presented as having a particular elliptical shape, the multifocal lens 208 can have any suitable shape, such as the different shapes shown in the various figures herein.

[0018] Examples of different types of multifocal lenses that can be used in the embodiments described herein will be described in more detail with respect to FIGS. 3A, 3B, 4A-4C, and 6A-6D. For example, as shown in FIGS. 3A, 3B, and 4A-4C, the multifocal lens 308 includes at least two refractive powers that produce two different corresponding focal points: a first refractive power 307 configured to correct the refractive error of the eye 100 for distance vision and a second refractive power 309 or “add power” for near vision. In certain embodiments, the first refractive power 307 corresponds to one optical element or region, while the second refractive power 309 corresponds to a separate second optical element or region. Further, the first refractive power 307 and the second refractive power 309 have optical centers that coincide (e.g., overlap) at the optical center 314 of the multifocal lens 308. Thus, it can be said that the first refractive power 307 and the second refractive power 309 share the optical center 314. In some embodiments, the second refractive power 309 is provided by a refractive element having a diameter less than the diameter of the pupil, such as a diameter less than about 1.5 mm, and a refractive power of about 2 diopters.

[0019] As shown and described with respect to FIGS. 3A and 3B, the multifocal lens 308 can be coupled (e.g., attached) to an external patient device, such as an ophthalmic test device, during use of the visual axis identification system 200. Thus, movement of the external patient device displaces the multifocal lens 308 with respect to the patient's eye 100. Alternatively, the multifocal lens 308 can be coupled to a trial frame 440 worn by the patient, as shown in FIGS. 4A-4C. Thus, rotation of the patient's head while the patient is wearing the trial frame 440 shifts the multifocal lens 308 with respect to the eye 100, and the shift is proportional to the distance between the multifocal lens 308 and the eye 100 and the angle of rotation of the patient's head. In a further embodiment, the optical center of the multifocal lens 308 includes a mark 312, such as a crosshair, for identifying the optical center of the multifocal lens 308 to facilitate positioning.

[0020] In another example shown in FIGS. 6A-6D, the multifocal lens 608 includes a reflective coating 603 formed on opposing side surfaces. Thus, the coating 603 replaces the functions of the refractive powers 307 and 309 and creates multiple foci using the light passing through the multifocal lens 608. Similar to the multifocal lens 308, the multifocal lens 608 can be coupled to an extra-patient device or an ophthalmic frame during use.

[0021] As described above, FIGS. 3A and 3B show simplified schematic views of the multifocal lens 308 when used with an extra-patient device, while FIGS. 4A-4C show simplified top and side schematic views of the multifocal lens 308 worn by a patient in an ophthalmic frame 440 according to a particular embodiment. FIG. 5 shows a flow diagram of a method 500 for identifying a location 130 of the visual axis 120 using the visual axis identification system 200 of FIG. 2 that may include a multifocal lens 308 coupled to an extra-patient device or an ophthalmic frame 440 according to some embodiments. Thus, FIGS. 3A, 3B, and 4A-4C are described in more detail herein together with FIG. 5 for clarity.

[0022] Generally, in operation 510, while using the visual axis identification system 200, the patient looks through the multifocal lens 308 and fixates on the fixation light beam 212. When the patient fixates on the fixation light beam 212, a focus F1 is formed on the fovea 122 where the center of the patient's visual field is located. The second refractive power 209 of the multifocal lens 308 also creates a second focus F 2 along the optical axis 318 of the multifocal lens 308 near the retina 116. 2 The focus F 1 is located at a lateral location different from the focus F

[0023] formed on the retina 116 due to, for example, an increased focusing (e.g., convergence) of the light rays in the fixation light beam 212 by the second refractive power 209 of the multifocal lens 308 having a positive diopter. 1 and the focus F 2As shown in FIGS. 3A and 4A, they are not aligned along the visual axis 120 (e.g., do not overlap each other or are not translationally shifted relative to each other), and two separated (e.g., not aligned, non-overlapping) images are formed on the patient's retina 116. Under these circumstances, the patient can visualize two "spots" formed by the fixation light beam 212: the first sharp image created by the focus F 1 and the second blurred (e.g., blurred or ambiguous) image created by the focus F 2 . However, when the foci F 1 and the focus F 2 overlap along the visual axis 120 as shown in FIGS. 3B and 4B, the patient can visualize two aligned (e.g., coincident, overlapping) images of the fixation light beam 212 on the retina 116. The alignment, overlap, or coincidence of the two images is herein referred to as the centers of the two images formed by the foci F 1 and F 2 being spatially aligned, overlapping, or coinciding. Such alignment occurs when the common optical center 314 of the refractive powers 307, 309 of the multifocal lens 308 is precisely on the visual axis 120 of the eye 100.

[0024] Accordingly, in operation 520, the multifocal lens 308 and / or the patient's head are moved to position the common optical center 314 of the multifocal lens 308 on the visual axis 120 of the eye 100. In the example shown in FIGS. 3A and 3B, the multifocal lens 308 coupled to the patient external device can move along the X-axis and Y-axis relative to the patient's head to align the focus F 2 with the focus F 1 on the visual axis 120 while the patient continuously maintains fixation on the fixation light beam 212. Alternatively, the patient can move the head along the X-axis and Y-axis to try to align or visually overlap the focus F 2 with the focus F 1 , and the multifocal lens 308 remains stationary while the patient continuously maintains fixation on the fixation light beam 212.

[0025] The focus F 2When aligned with the visual axis 120, the patient sees two overlapping images or spots with their centers spatially coinciding. Even while they are aligned with each other, the first image or spot formed by the focal point F1 is sharp, and the second image or spot formed by the focal point F2 is somewhat blurred. As shown in FIG. 3B, when the focal point F 2 is the focal point F on the visual axis 120 1 When overlapping, the line connecting the output point of the fixation light source 202 (e.g., the origin of the fixation light beam 212) to the common optical center 314 of the multifocal lens 308 intersects the front surface (e.g., the pupil surface) of the cornea 104 at the exact X / Y position of the visual axis 120.

[0026] Referring now to the embodiments of FIGS. 4A - 4C, instead of coupling the multifocal lens 308 to an external device of the patient, the multifocal lens 308 is disposed in an ophthalmic frame 440 worn by the patient. In such an embodiment, while the patient wears the ophthalmic frame 440 and continuously maintains fixation on the fixation light beam 212, the patient moves (e.g., rotates or tilts up, down, left, and right) the head 460 to attempt to align or visually overlap the focal point F 2 with the focal point F 1 on the visual axis 120.

[0027] As shown in FIG. 4A, when the patient fixates on the fixation light beam 212, the first focal point F1 is formed on the fovea 122. Since the optical center 314 of the multifocal lens 308 is not aligned with the visual axis 120, the multifocal lens 308 forms a second focal point F 2 within the eyeball space of the eye 100 along an optical axis 318 that does not overlap the visual axis 120. In FIG. 4B, the patient moves or rotates the head 460 while focusing on the fixation light beam 212 to align the focal point F 2 with the focal point F 1 on the visual axis 120, and thus sees two images or spots with their centers spatially coinciding, formed by the fixation light beam 212. As described above, the focal point F 2 is the focal point F on the visual axis 120 1When overlapping, the line connecting the fixation light source 202 to the common optical center 314 of the multifocal lens 308 within the ophthalmic frame 440 intersects the anterior corneal surface at the location 130 of the visual axis 120.

[0028] For clarity, FIG. 4C shows a schematic side view of a patient wearing the multifocal lens 308 when disposed within the ophthalmic frame 440. The patient rotates the head 460 in a “yes” (e.g., Y rotation) or “no” (e.g., X rotation) movement when fixing the gaze on the fixation light beam 212. Due to the distance between the patient's eye 100 and the multifocal lens 308, the rotational movement of the patient's head 460 displaces the multifocal lens 308 relative to the patient's eye 100 and the fixation light beam 212. This displacement has the same effect as the movement of the multifocal lens 308 described with reference to FIGS. 3A and 3B. Thus for example, if the distance between the eye 100 and the multifocal lens 308 is 12 mm and the patient rotates the head 5 degrees in either an X movement or a Y movement while maintaining fixation on the fixation light beam 212, the multifocal lens 308 moves (12 mm * tan(5°)) = 1.05 mm relative to the eye 100.

[0029] Simultaneous with the movement of the patient's head 460 and / or the multifocal lens 308, in operation 530, the imaging camera 204 captures an image or video of the multifocal lens 308 and the eye 100. Generally, the imaging camera 204 captures the image from the direction along which the fixation light beam 212 moves to the eye 100. In some examples, the video recording of the eye 100 during method 500 can increase the accuracy in identifying the location 130 of the visual axis 120. The image or video of the multifocal lens 308 and the eye 100 is then relayed to the image processing system 206, which identifies the location of the eye 100 relative to the optical center 314 of the multifocal lens 308 during the movement of the patient's head and / or the multifocal lens 308. As described above, the identification of the X / Y location of the eye 100 can be achieved by using the vasculature of the sclera of the eye 100 as a landmark. In some examples, the optical center 314 is indicated using a crosshair 312 on the multifocal lens 308 for identification by the imaging camera 204 and / or the image processing system 206.

[0030] In operation 540, the movement of the patient's head and / or the multifocal lens 308 is continued until the patient reports seeing an overlapping image of the fixation light beam 212 such that the centers of two or more images coincide. Then, in operation 550, the image processing system 206 identifies the location 130 of the patient's visual axis 120. Generally, the line connecting the output point of the fixation light source 202 to the optical center 314 of the multifocal lens 308 intersects the outer surface of the cornea 104 at the exact location of the visual axis 120 when the patient visualizes two images with their centers spatially aligned, and thus, by identifying this intersection point, the location 130 of the visual axis 120 can be discerned.

[0031] In some embodiments, when the patient reports a visual overlap of foci F 1 and F 2 a single image of the eye 100 and the multifocal lens 308 is collected by the imaging camera 204 and analyzed by the imaging processing system 206. Thus, the identification of the location 130 of the visual axis 120 can be a unique X, Y coordinate specification. In other embodiments, while the patient attempts to maintain a visual overlap of foci F 1 and F 2 a video or a series of images is collected by the imaging camera 204 and analyzed by the image processing system 206. The video or series of images can be collected over any desired time period such as 5 seconds, 10 seconds, 15 seconds, 20 seconds, 25 seconds, or any other suitable time period. For example, the time period can be from about 5 seconds to about 60 seconds, such as from about 5 seconds to about 30 seconds, such as from about 10 seconds to about 20 seconds. During this time period, the patient is instructed to attempt and maintain fixation to view an overlapping image of the fixation light beam 212. Then the image processing system 206 can analyze the video or series of images to identify the average X / Y location of the optical center 314 of the multifocal lens 308 relative to the X / Y location of the eye 100, and thus, compensate for any unintentional patient eye and / or head movement while focusing on the fixation light beam 212. Thus, the identification of the location 130 of the visual axis 120 can be an average X / Y coordinate specification.

[0032] In some embodiments, the fixation light beam 212 can include two or more wavelengths or various wavelengths having different reflection characteristics through the multifocal lens 308. In such embodiments, unwanted reflections of the fixation light beam 212 towards the imaging camera 204 can be eliminated or significantly reduced during the use of the visual axis identification system 200. In one example, the fixation light beam 212 can include a first wavelength having a first frequency at which the multifocal lens 308 is highly reflective and the imaging camera 204 has no sensitivity. The fixation light beam 212 can also include a second wavelength having a second frequency at which the multifocal lens 308 has high transmissivity, the eye 100 has no sensitivity, and the imaging camera 204 has high sensitivity. Thus, the fixation light beam 212 can be separated (e.g., filtered) by the multifocal lens 308 such that only the light of the second wavelength is transmitted to the imaging camera 204. The spectral separation of the fixation light beam 212 into two or more wavelengths to which the eye 100 and the imaging camera 204 have different sensitivities reduces the disturbing effect of the reflection by the multifocal lens 308 and increases the accuracy of the visual axis identification system 200 in identifying the location 130 of the visual axis 120.

[0033] Figures 6A - 6D show simplified schematic views of an alternately coated multifocal lens 608 that can be used in conjunction with the visual axis identification system 200 and method 500 according to some embodiments. Figures 7A and 7B show images formed on the retina 116 of a patient while using the coated multifocal lens 608 according to some embodiments. Thus, for clarity, Figures 6A - 6D, 7A, and 7B are described together herein.

[0034] The coated multifocal lens 608 shown in FIGS. 6A-6D is substantially similar to the multifocal lenses 208 and 308 described above, but includes a coating 603 disposed on its two main surfaces 611a and 611b. The coating 603 partially reflects and partially transmits the fixation light beam 212. In some embodiments, the coating 603 can spectrally separate the fixation light beam 212 and direct that light onto the imaging camera 204. For example, the reflection peak (e.g., maximum reflection) of the coating 603 can correspond to the wavelength of the fixation light beam 212 that the patient visualizes. In a further example, the coating 603 can have zero reflectivity at the wavelengths of light detected by the imaging camera 204. Thus, unwanted reflections of the fixation light beam 212 towards the imaging camera 204 can be eliminated or significantly reduced by utilizing the coated multifocal lens 608, enabling the location 130 of the visual axis 120 to be more accurately identified during method 500.

[0035] The use of the coating 603 on the coated multifocal lens 608 further enables the formation of two or more foci depending on its reflectivity. Generally, the coating 603 enables the formation of an infinite number of foci and images, the intensity of which decreases according to a geometric progression. However, the human eye 100 cannot perceive all the images, and thus perceives only a limited number of them. The number of formed, perceptible or visible foci can be controlled by changing the reflection characteristics of the coating 603. For clarity, only four foci F L0 、F L1 、F L2 、and F L3 are shown in FIGS. 6A-6D. When the fixation light beam 212 passes through the coated multifocal lens 608 at a location other than the optical center 614, multiple foci F L0 、F L1 、F L2 、and F L3is translated parallel to the optical axis 618 (shown in FIGS. 6A and 6C), and the patient sees non-overlapping spots. However, when the fixation light beam 212 passes through the optical center 614 of the coated multifocal lens 608 and is parallel to its optical axis 618 (shown in FIG. 6D), the foci F L0 , F L1 , F L2 , and F L3 visually overlap on the optical axis 618 of the coated multifocal lens 608, and the patient sees overlapping spots.

[0036] The multifocal lens 608 can be utilized to localize the visual axis 120 of the patient's eye 100 via a method that is substantially similar to that described with reference to the multifocal lenses 208 and 308 and the method 500. Generally, the multifocal lens 608 translates in the X or Y direction relative to the patient's eye 100 when the patient is focusing on the fixation light beam 212. When the patient visualizes overlapping spots whose centers are spatially coincident, the fixation light beam 212 is directed through the optical center 614 of the multifocal lens 608, and the optical center 614 is precisely on the visual axis 120 of the eye 100, thereby enabling the identification of the visual axis 120.

[0037] FIG. 7A shows the patient's view when looking through the fixation light beam 212 through a location off the center of the coated multifocal lens 608. Here, the foci F L0 , F L1 , F L2 , and F L3 are not aligned on both the optical axis 618 and the visual axis 120. The patient sees a generally linear row of spots 715 of varying sizes and sharpness. FIG. 7B shows what the patient can see when the fixation light beam 212 passes through the optical center 614 of the coated multifocal lens 608. The foci F L0 , F L1 , F L2 , and F L3 visually overlap with each other on the optical axis 618 and the visual axis 120. During the method 500, the use of a lens that forms two or more foci for alignment enables the location of the visual axis 120 to be specified more precisely and accurately compared to a lens that forms a single focus.

[0038] The above-described method and apparatus provide a novel visual axis identification system that can be used to improve the efficacy of ophthalmic procedures such as fitting of corrective lenses, refractive surgery, intraocular lens implantation, and treatment of presbyopia including multifocal corneal inlays. The described visual axis identification system can be further used in combination with any suitable ophthalmic diagnostic device. Examples of suitable diagnostic devices include corneal topographers, optical coherence tomography devices, wavefront meters (e.g., aberrometers), image-guided biometers, surgical microscopes, and other image-based diagnostic devices. In some examples, the visual axis identification system 200 can be used in combination with the CENTURION®, INFINITI™, Verion™, ORA™ systems, LenSx®, LuxOR® LX3 platforms manufactured by Alcon located in Fort Worth, Texas. In some examples, the visual axis identification system 200 can be used with ophthalmic platforms provided by other manufacturers.

[0039] Embodiment Example Embodiment 1: A method for determining the location of the visual axis of a patient's eye, comprising: placing a multifocal optical lens adjacent to the patient's eye, the multifocal optical lens having two or more refractive powers with corresponding spatially coincident optical centers at the optical center of the multifocal optical lens; generating a fixation light and directing it at the patient's eye, the fixation light forming two or more images at a focus near the retina of the patient's eye, the two or more images corresponding to the two or more refractive powers of the multifocal optical lens; capturing an image of the patient's eye and the multifocal optical lens along the direction of the fixation light; determining the X / Y location of the patient's eye relative to the X / Y location of the optical center of the multifocal optical lens; moving the multifocal optical lens relative to the patient's eye while the patient maintains fixation on the fixation light until the centers of the two or more images coincide in the patient's view; and identifying the location of the visual axis of the patient's eye on the pupil plane of the patient's eye, the location of the visual axis corresponding to the location of the optical center of the multifocal optical lens as viewed from the direction of the fixation light. A method comprising the above.

[0040] Embodiment 2: The method according to Embodiment 1, wherein the multifocal optical lens is coupled to an ophthalmic frame worn by a patient.

[0041] Embodiment 3: The method according to Embodiment 1, wherein the multifocal optical lens is coupled to an external device of the patient.

[0042] Embodiment 4: A system for identifying the location of the visual axis of a patient's eye, comprising a multifocal optical lens, a detector configured to track the movement of the eye, the detector being further configured to capture an image of the multifocal optical lens relative to the location of the eye, and a processing system configured to identify the location of the visual axis of the eye on the front surface of the eye based on the image captured by the detector, wherein the visual axis of the eye corresponds to the optical center of the multifocal optical lens when the centers of two or more foci of the multifocal optical lens coincide in the patient's view.

[0043] Embodiment 5: The system according to Embodiment 4, wherein the multifocal optical lens is coupled to an ophthalmic frame.

[0044] Embodiment 6: The system according to Embodiment 4, wherein the multifocal optical lens is coupled to an external device of the patient.

[0045] Embodiment 7: The system according to Embodiment 4, wherein the detector is an infrared camera.

[0046] Embodiment 8: The system according to Embodiment 7, wherein the infrared camera is configured to track the movement of the eye by detecting landmarks of the vasculature of the sclera of the eye.

[0047] Embodiment 9: The system according to Embodiment 4, wherein the multifocal optical lens includes an axicon.

[0048] The foregoing relates to embodiments of the present disclosure, but other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof, the scope of which is determined by the following claims.According to aspect (1), a method for identifying the location of the visual axis of a patient's eye, comprising: placing a multifocal optical lens adjacent to the patient's eye, the multifocal optical lens having two or more refractive powers with corresponding spatially coincident optical centers at the optical center of the multifocal optical lens; generating fixation light and directing it towards the patient's eye, the fixation light forming two or more images at a focus near the retina of the patient's eye, the two or more images corresponding to the two or more refractive powers of the multifocal optical lens; capturing an image of the patient's eye and the multifocal optical lens along the direction of the fixation light; identifying the X / Y location of the patient's eye relative to the X / Y location of the optical center of the multifocal optical lens; moving the multifocal optical lens relative to the patient's eye while the patient maintains fixation on the fixation light until the centers of the two or more images coincide in the patient's view; identifying the location of the visual axis of the patient's eye on the pupil plane of the patient's eye, the location of the visual axis corresponding to the location of the optical center of the multifocal optical lens as viewed from the direction of the fixation light; A method comprising the above steps. According to aspect (2), the multifocal optical lens has optical coatings on two or more of its surfaces. According to aspect (3), the multifocal optical lens is configured to form three or more foci within the patient's eye. According to aspect (4), the location of the visual axis further corresponds to the location of the optical center of the multifocal optical lens when the centers of the two or more images coincide with each other in the patient's view. According to aspect (5), the spectrum of the fixation light is separated into two or more wavelength ranges having different refractive and reflective characteristics through the multifocal optical lens. According to aspect (6), the optical center of the multifocal optical lens is marked by a crosshair. According to aspect (7), identifying the location of the visual axis of the patient's eye comprises: During the time period in which the patient maintains fixation on the fixation light so as to view the coincidence image formed by the fixation light, spatially averaging the X / Y location of the optical center of the multifocal optical lens with respect to the location of the patient's eye at that place. According to aspect (8), the time period is from about 5 seconds to about 60 seconds. According to aspect (9), the multifocal optical lens is a complex diffractive optical element configured to form an ultra-long focal line. According to aspect (10), the multifocal optical lens includes an axicon. According to aspect (11), the multifocal optical lens includes an aspherical extended depth of focus lens. According to aspect (12), a system for identifying the location of the visual axis of a patient's eye, a multifocal optical lens, a detector configured to track the movement of the eye, the detector being further configured to capture an image of the multifocal optical lens with respect to the location of the eye, a processing system configured to identify the location of the visual axis of the eye on the front surface of the eye based on the image captured by the detector, wherein the visual axis of the eye corresponds to the optical center of the multifocal optical lens when the centers of two or more foci of the multifocal optical lens coincide with the image in the patient's view and form an overlapping image, A system comprising. According to aspect (13), the multifocal optical lens is a complex diffractive optical element configured to form an ultra-long focal line. According to aspect (14), the multifocal optical lens includes an aspherical extended depth of focus lens. According to aspect (15), the processing system configured to identify the location of the visual axis of the eye includes the processing system configured to average the X / Y location of the optical center of the multifocal optical lens with respect to the location of the eye during the time period in which the patient maintains fixation on the fixation light so as to view the overlapping image formed by the fixation light.

Claims

1. A system for identifying the location of the visual axis of a patient's eye, comprising: A multifocal optical lens; A detector configured to track the movement of the eye, the detector being further configured to capture an image of the multifocal optical lens with respect to the location of the eye; A processing system configured to identify the location of the visual axis of the eye on the front surface of the eye based on the image captured by the detector, wherein the location of the visual axis is identified when the patient reports seeing an overlapping image such that the centers of two or more foci of the multifocal optical lens coincide with the image in the patient's view; A system comprising the above.

2. The system according to claim 1, wherein the multifocal optical lens is a complex diffractive optical element configured to form an ultra-long focal line.

3. The system according to claim 2, wherein the multifocal optical lens includes an aspherical extended depth of focus lens.

4. The processing system configured to identify the location of the visual axis of the eye comprises: The system according to claim 1, including the processing system configured to average the X / Y location of the optical center of the multifocal optical lens with respect to the location of the eye during a time period when the patient maintains fixation on the fixation light such that the patient sees an overlapping image formed by the fixation light.

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