Patent Publication Number: US-10779727-B2

Title: Lens system for inspection of an eye

Description:
This application is a Continuation of U.S. patent application Ser. No. 15/525,268, filed May 8, 2017, which is a National Stage Application of PCT/IL2015/051076, filed Nov. 9, 2015, which claims benefit of Israeli Patent Application No. 235594, filed Nov. 9, 2014, which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications. 
    
    
     FIELD OF THE DISCLOSED TECHNIQUE 
     The disclosed technique relates to a lens for the surgical field, in general, and to methods and systems for observing a retina of an eye by employing a retinal-surgery lens incorporating a mirror arranged to reflect light onto the retina, in particular. 
     BACKGROUND OF THE DISCLOSED TECHNIQUE 
     In the human vision system, the retina is a light-sensitive layer of tissue, covering the inner surface of the eye. An image of a viewed scene is created on the retina (i.e., through the eye lens). Light impinging on the retina triggers nerve impulses sent to visual areas of the brain. 
     Retinal surgeries, as known in the art, involve the placement of a macular lens on the eye and insertion of an illumination optical fiber into the eye ball for illuminating the retina. For example, one surgeon (or a fixture) holds the macular lens on the top surface of the eye, the cornea, while another holds the illumination fiber and other surgical tools. Thus, the illumination fibers are aimed manually. Additionally, the distribution angle of the illuminating fiber beam (i.e., or the illuminated spot generated thereby) is relatively narrow. Therefore, the surgeon holding the fiber has to constantly redirect the illumination fiber for illuminating the area of interest investigated under a microscope. 
     Reference is now made to US Patent Application Publication No. 2012/0050683 to Yates, entitled “Self-Illuminated Handheld Lens for Retinal Examination and Photography and Related Method thereof”. This publication is directed to a handheld fundus lens with integrated lighting fibers. The hand held fundus lens of this publication provides illumination to the patient&#39;s retina from a point source of light through fiber optics strands. The light source is positioned outside the lens and is directly coupled to the fiber optic strands. A light channel is ground into the contact lens, and the fiber optic strands are inserted into this light channel. The fiber optic strands are formed into an illumination ring abutting the contact lens. 
     WO 95/14254 to Donald A. Volk entitled “Indirect ophthalmoscopy lens system and adapter lenses” is directed to an ophthalmoscopic or gonioscopic lens system. The indirect ophthalmoscopy lens comprises a hand-held, pre-set or fixed system having at least two lens elements each having first and second surfaces. The at least two lens elements are positioned adjacent one another in a housing, such that the refractive properties of each are combined to converge light from an illumination light source to the entrance pupil of the patient&#39;s eye to illuminate the fundus thereof and form a fundus image to be viewed. The adapter lens systems of this invention are designed for use with an associated ophthalmoscopic lens, enabling selective modification of the optical characteristics of the ophthalmoscopic lens system in a predetermined manner. 
     US 2009/0185135 to Donald A. Volk entitled “Real image forming eye examination lens utilizing two reflective surfaces providing upright image” describes a diagnostic and therapeutic contact lens for use with biomicroscopes for the examination and treatment of structures of the eye. The lens comprises a contacting surface adapted for placement on the cornea of an eye, two reflecting surfaces, and a refracting surface. A light ray emanating from the structure of the eye enters the lens and contributes to the formation of a correctly oriented real image. The light ray is reflected in an ordered sequence of reflections, first as a negative reflection in a posterior direction from an anterior reflecting surface and next as a positive reflection in an anterior direction from a posterior reflecting surface. The light ray contributes to forming the image of the structure of the eye either anterior to the lens or within the lens and proceeds along a pathway to the objective lens of the biomicroscope used for stereoscopic viewing and image scanning. 
     SUMMARY OF THE PRESENT DISCLOSED TECHNIQUE 
     It is an object of the disclosed technique to provide a novel surgical lens system including a lens and a reflective element. The lens is placed on, or above, a cornea of an eye of a subject for enabling inspection of the eye. The reflective element is incorporated into the lens. The reflective element reflects a light beam toward the eye of the subject. The reflective element increases the divergence of the light beam, such that the divergence of the reflected light beam is larger than the divergence of the light beam. The light beam is emitted by a non-invasive light source positioned externally to the eye. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosed technique will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: 
         FIG. 1  is a schematic illustration of a surgical lens system, constructed and operative in accordance with an embodiment of the disclosed technique; 
         FIG. 2  is a schematic illustration of a surgical lens system, constructed and operative in accordance with another embodiment of the disclosed technique; 
         FIG. 3  is a schematic illustration of a surgical lens system, constructed and operative in accordance with a further embodiment of the disclosed technique; and 
         FIG. 4  is a schematic illustration of a surgical lens system, constructed and operative in accordance with another embodiment of the disclosed technique. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The disclosed technique overcomes the disadvantages of the prior art by providing a macular lens incorporating a mirror and a light guide. The light guide directs an illumination light beam from a light source to the mirror. The mirror reflects the light beam toward the eye of a subject to illuminate the eye (e.g., to illuminate the retina of the subject for inspection). Additionally, the mirror may have optical power and be configured to increase the divergence of the reflected light beam. In accordance with an embodiment of the disclosed technique, the reflected light beam passes through the macular lens, which further increases the divergence of the reflected light beam. In other words, the mirror (and possibly also the macular lens) increases the diameter of the illumination light beam on the retina of the subject. 
     In accordance with another embodiment of the disclosed technique the macular lens (including the incorporated mirror) is disposable. In this manner, a physician can inspect the eye of a subject via such a disposable macular lens and dispose of the macular lens afterwards, employing another such macular for inspecting another subject. 
     The term “beam diameter” as referred to herein below relates to the diameter of the cross section of a light beam on a plane perpendicular to the beam axis. That is, the beam diameter is the diameter of the spot the beam lights on a plane perpendicular to the beam axis. The term “beam divergence” as referred to herein below relates to the increase in beam diameter with distance (i.e., the beam angular distribution). The term “inspection” as referred to herein with respect to inspection of the eye of a subject, relates to inspection of the eye or of different portions of the eye for various purposes. For example, the inspection can relate to observation by a physician for medical diagnostic, for retinal surgery or for imaging in general. The inspection can further relate to other purposes, such retinal scan for biometric identification, and any other purpose which requires inspecting the eye or various portions thereof. 
     Reference is now made to  FIG. 1 , which is a schematic illustration of a surgical lens system, generally referenced  100 , constructed and operative in accordance with an embodiment of the disclosed technique. 
     Lens system  100  includes a surgical lens  102 , a mirror  104  and a light source  106 . In general, light source  106  is positioned outside the field of view (FOV) of the lens. In the embodiment shown in  FIG. 1  light source  106  is positioned perpendicular to the FOV of lens  102 . In other embodiments, light source  106  can be positioned also substantially perpendicular to the FOV of the lens (i.e. in a range of −/+10 degrees). Mirror  104  is incorporated into lens  102 , for example, at the center of surgical lens  102  (i.e., the center on a plane perpendicular to the optical axis of surgical lens  102 ). The position of mirror  104  relative to the center of surgical lens  102  can affect the illumination characteristics (characteristics like illumination uniformity, stray lights reflected to the optical system or camera, illumination field of view coverage etc.) In general, mirror  104  can be placed at different positions relative to lens  102  as long as it is located at the central region of lens  102  away from the periphery thereof. Light source  106  is optically coupled with mirror  104 . Lens system  100  may further include a waveguide (not shown) optically coupled between light source  106  and mirror  104 . 
     As used in this disclosure the term ‘optically coupled’ describes an aspect of the optical relations between light source  106  and mirror  104 . Light emitted from light source  106  is conveyed to mirror  104  by using different techniques. As an example, an exit aperture located in light source  106  is placed near a specific location on the lens (an entrance aperture). A mechanical fixture can be used in order to correctly position the exit aperture near the entrance aperture. The light then exits the light source exit aperture and enters directly into the lens through the entrance aperture. Subsequently to entering the lens, the light travels through a waveguide that directs the light to the mirror. The waveguide is optionally selected from a recess, a depression, a change in the lens index of refraction or an implantation of different material in the lens, etc. The light source aperture size, the divergence angle, the entrance aperture in the lens and waveguide can be designed according to the user&#39;s requirements. In a further embodiment of the disclosed technique, a small light fiber is tunneled through the lens to reach a point located a short distance from the mirror and thus illuminate the mirror directly. In an additional embodiment of the disclosed technique, the light can be illuminated directly towards the mirror (with no waveguide), using a laser source (or other) with a very narrow angle of divergence. 
     Surgical lens  102  is attached to an eye  110  of a subject and in particular is placed on a cornea  114  of eye  110  similarly to a contact lens, or at a short distance from the cornea. Therefore, lens  102  can be of various sizes to fit various subjects. For example, for inspecting the eye of a child, a user would use a smaller lens than for an adult. The eyes of different users can vary by size, cornea convexity, and the like. Surgical lens  102  is also referred to herein below as macular lens  102  or simply lens  102 . 
     Lens  102  is employed for inspection of eye  110  or of portions thereof, such as the retina, the eye lens, and the like. The inspection can be performed by employing the macular lens alone or employing the macular lens as a component of an inspection system including additional components. For example, lens  102  is employed for retinal diagnostic and surgical operations, and enables a surgical microscope (e.g., ophthalmic microscope) to image a retina  112  via cornea  114  and eye lens  116 . When inspecting the subject&#39;s retina via a microscope, one should add a relay component to the microscope for adapting the microscope to compensate for light divergence by the eye lens of subject. The macular lens of the disclosed technique serves as such relay component. For example, macular lens  102  is an aspheric fundus lens. 
     Lens  102  can be of varying optical power, as required by the inspection task at hand. For example, a lens for inspecting the retina might differ from a lens for inspective the eye lens of the subject. The differences can relate to the focal distance, the optical power, the field of view (FOV), and other optical and physical parameters of the lens. 
     Mirror  104  is a reflective element, also referred to herein below as reflective element  104 . Mirror  104  may be partially reflective as a function of power or wavelength (e.g., reflecting only a selected waveband). Mirror  104  is configured to reflect (i.e., redirect) light received from light source  106  toward eye  110 . That is, mirror  104  is constructed, positioned and coupled with the other components of surgical lens system  100  in such a way that it reflects the light produced by light source  106  toward eye  110 . 
     Mirror  104  may further be configured to increase the divergence of the light reflected thereby. The divergence increase of mirror  104  is adapted to the inspection task at hand. For example, the user can use a different lens system having a different mirror (differing by its beam divergence increase) for different inspection tasks. Generally, mirror  104  increases the divergence of the light beam, such that the FOV of lens  102  would be illuminated. It is noted that the divergence of the light beam may further be increased by lens  102  and by the eye lens, which should be considered when configuring the divergence increase of mirror  104 . 
     Mirror  104  can be composed of several elements. For example, mirror  104  can include several reflecting surfaces, each with different optical power (or with no optical power). Mirror  104  can include a flat mirror (i.e., a reflecting component) and a lens (i.e., a divergence increasing component) coupled therewith. Alternatively, reflective element  104  can be replaced by other optical elements for changing the direction of light, such as a prism, a diffraction grating, or a beam splitter. Generally speaking, the reflective element should redirect the illumination beam toward the eye of the subject. Additionally, the reflective element may be configured to increase the beam divergence of the illumination beam as detailed above. 
     As mentioned above the mirror (i.e., the reflective element) can be coupled with other optical elements. The optical elements are employed for augmenting the function of the mirror (e.g., flat mirror coupled with a lens), or for complementing it (e.g., both the mirror and the lens increase the beam divergence). The optical element coupled with the mirror can serve other functions as well, such as improving the light uniformity. 
     The beam divergence angle of the reflected light covers the field of view (FOV) of macular lens  102 . In this manner, an inspected area, inspected via lens  102 , is illuminated. Moreover, the reflected light illuminates the FOV of macular lens  102  in a uniform manner. It is noted that, non-uniform illumination may affect images of the retina and may lead to erroneous diagnostics. 
     Mirror  104  can be incorporated into lens  102 , located within a niche within lens  102  or coupled with lens  102  on either side of lens  102 . In case mirror  104  is located within lens  102  or coupled to the side of lens  102  further from the eye, the light reflected by the mirror passes through at least a portion of lens  102 . In this case, lens  102  increases the divergence of the reflected light beam, thereby augmenting the beam divergence increase of mirror  104 . Additionally, mirror  104  is configured such that eye lens  116  further increases the divergence of the reflected light beam. It is noted that mirror  104  partially occludes the FOV of lens system  100 . Therefore, mirror  104  should be small enough such that the occlusion would not adversely affect the inspection of the eye. For example, mirror  104  can have a diameter ranging between 1-3 millimeters. Mirror  104  can be positioned at different heights along the optical axis. The occlusion severity and type is a function of the mirror height. According to the disclosed technique, the occlusion of a mirror positioned outside of the focal plane, will cause certain effects like decreasing the illumination level, the sharpness of the image etc. but will not cause complete obstruction of portions of the perceived image. Contrary to the disclosed technique, the occlusion of a mirror positioned in the focal plane, will cause obstruction of the perceived image. 
     In accordance with an embodiment of the disclosed technique, mirror  104  is positioned at the center of lens  102  along the optical axis of lens  102 . In such a case, the reflected light beam and the FOV of macular lens  102  are coaxial. Put another way, reflected light beam  120  provides zero-angle illumination. In accordance with another embodiment mirror  104  is positioned off-axis. For example, mirror  104  is positioned off the axis of macular lens  102  but is still located in the central region of macular lens  102  away from the periphery of lens  102 . 
     In accordance with another embodiment of the disclosed technique, mirror  104  can have various optical properties, for affecting the reflected light beam. For example, mirror  104  can affect the polarity, the wavelength (e.g., by blocking a selected waveband), or other properties of the light beam. Mirror  104  can be coated with various coatings for inducing these optical properties. 
     In accordance with yet another embodiment of the disclosed technique, mirror  104  can be coupled to lens  102  via a mounting mechanism which allows mirror  104  to be moved. Thereby, mirror  104  can be employed as a scanning mirror for illuminating different areas of the eye of the subject. 
     Light source  106 , including an output port of light source  106  (not referenced), is positioned externally to the eye. In other words, light source  106  is a noninvasive light source. Light source  106  is configured to generate illumination light beam  118 . Light source projects light beam  118  toward mirror  104  (or toward a waveguide of surgical lens system  100  leading to mirror  104  and incorporated into macular lens  102 ). In accordance with an embodiment of the disclosed technique, light source  106  produces a narrow light beam  118 , which is thereafter diverged by mirror  104 , macular lens  102  and eye lens  106  to illuminate the FOV of macular lens  102 . 
     Light source  106  can produce illumination light at any desired light wavelength, or other illumination characteristics (e.g., wavelength, polarization, intensity and the like), as required by the user and the task at hand. Additionally, the illumination beam can be modulated. The light source can produce light pulses instead of a continuous beam. The illumination can be synchronized with, or otherwise controlled, by an external device, such as an imaging device. Generally, the light source produces the illumination required to the task at hand, and the mirror directs the illumination beam (or pulse) toward the inspected area. 
     It is noted that the light source can be coupled with the lens system of the disclosed technique via intermediate elements such as a fiber and a connector. For example, the light source can be a Light Emitting Diode (LED) mechanically (or opto-mechanically) connected to the lens. 
     During operation, a user (e.g., an ophthalmologist) places macular lens  102  on cornea  114  and turns on light source  106 . Light source  106  directs light beam  118  toward reflective element  104 . Reflective element  104  reflects light beam  118  toward eye  110 . In other words, reflective element directs a reflected light beam  120  toward eye  110 . The user inspects eye  110  (illuminated by reflected light beam  120 ) via macular lens  102 . 
     As can be seen in  FIG. 1 , reflective element  104  increases the divergence of reflected light beam  120 . That is, the divergence of reflected light beam  120  is larger than that of light beam  118 . As can further be seen in  FIG. 1 , each of macular lens  102  and eye lens  116  further increases the divergence of reflected light beam  120 . It is noted that the divergence angle of reflected light beam  120  covers the FOV of macular lens  102 , such that the inspected portion of retina  112  is illuminated. Additionally, reflected light beam  120  illuminates the inspected portion of retina  112  in a uniform manner. 
     In accordance with an embodiment of the disclosed technique, the user can hold the lens via a holder (not shown). The light source can be incorporated into (or connected to) the holder. Alternatively, the lens can be held in place by a mechanical fixture (not shown). The light source can be incorporated into (or connected to) the mechanical fixture. 
     In accordance with another embodiment of the disclosed technique, macular lens  102  (including incorporated mirror  104  and the optional incorporated waveguide) is disposable. In this manner, the user places lens  102  over cornea  114  of the subject, and couples it to light source  106 . The user inspects eye  110  via lens  102 , and thereafter disposes of lens  102 . The user employs a new disposable lens  102  for the next subject. Light source  106  can be reused. As the lens system is disposable and is employed for a single subject, different lens systems can be of different sizes for adapting to various users. Additionally, the reflective elements can be of various optical properties, such as various degrees of divergence increase, for different inspection tasks. In accordance with an alternative embodiment, the macular lens can be reused (after being sanitized) for a plurality of subjects. Further alternatively, some elements of the macular lens system are reusable and some are disposable. For example the light source and the lens holder are reusable, while the lens and the incorporated mirror and waveguide, are disposable. 
     In accordance with yet another embodiment of the disclosed technique, the lens system includes a zooming mechanism for controlling the zoom of the light beam. For example, the mirror is coupled with lenses which serve as a zoom mechanism for the illumination light beam. Alternatively, the light source can be moved with respect to the mirror for varying the zoom of the illumination beam. 
     In accordance with yet another embodiment of the disclosed technique, system  100  is employed for inspection of other body cavities which require illumination, such as the ears of the subject. System  100  is placed over the body cavity, the mirror reflects the illumination beam toward the cavity, and the user inspects the illuminated cavity via the lens. 
     Reference is now made to  FIG. 2 , which is a schematic illustration of a surgical lens system, generally referenced  200 , constructed and operative in accordance with another embodiment of the disclosed technique.  FIG. 2 , depicts a cross section of surgical lens system  200  along a plane perpendicular to the optical axis of the lens. Lens system  200  includes a lens  202 , a mirror  204 , a light source  206  and a waveguide  208  (or a light guide  210 ). Mirror  204  and waveguide  208  are incorporated into lens  202 . Mirror  204  is optically coupled with light source  206  via waveguide  208 . That is, a light beam  210  irradiated by light source  206  enters waveguide  208  and is directed thereby toward mirror  204 . Each of lens  202 , mirror  204  and light source  206  is substantially similar to lens  102 , mirror  104 , and light source  106 , of  FIG. 1 , respectively. Waveguide  208  (also referred to herein as light guide  208 ) is an optical element for directing light from one end of waveguide  208  (coupled with light source  206 ) to the opposite end of waveguide  208  (coupled with mirror  204 ). For example, waveguide  208  can be an optical fiber, a dedicated structure within lens  102 , a series of mirrors or other optical elements that can guide light, and the like. 
     A user holds (or places) lens  102  over a cornea of an eye of a subject. Light source  206  irradiates illumination beam  210  into waveguide  208 . Waveguide  208  guides illumination beam  210  toward mirror  204 . Mirror  204  reflects illumination beam  210  toward the eye of the subject, illuminating the eye for inspection via lens  202 . As can be seen in  FIG. 2 , mirror  204  is positioned at the center of lens  202  (i.e., along the optical axis of lens  202 ). Thereby, the reflected light beam and the FOV of lens  202  are coaxial (i.e., zero-angle illumination). Alternatively, mirror  204  can be located off-axis. 
     Reference is now made to  FIG. 3 , which is a schematic illustration of a surgical lens system, generally referenced  300 , constructed and operative in accordance with a further embodiment of the disclosed technique. Lens system  300  includes a surgical lens  302 , a first mirror  304 A, a second mirror  304 B, and a light source  306 . Mirrors  304 A and  304 B are incorporated into lens  302 . Light source  306  is optically coupled with mirror  304 . Lens system  300  can further include a waveguide (not shown) coupled between light source  306  and each of mirrors  304 A and  304 B for guiding light irradiated by light source  306  toward mirrors  304 A and  304 B. 
     Light source produces a light beam composed of a first light beam portion  318 A and a second light beam portion  318 B (light beams  318 A and  318 B). First light beam portion  318 A impinges on the reflective surface of mirror  304 A and is reflected thereby as first reflected light beam  320 A. Second light beam portion  318 B impinges on the reflective surface of mirror  304 B and is reflected thereby as second reflected light beam  320 B. Each of mirrors  304 A and  304 B also increases the divergence of the respective reflected light beam. That is, mirror  304 A increases the divergence of reflected light beam  320 A, and mirror  304 B increases the divergence of reflected light beam  320 B. Each of lens  302  and eye lens  316  further increases the divergence of reflected light beams  320 A and  320 B. Reflected light beams  320 A and  320 B illuminate the FOV of lens  302 , thereby allowing inspection of eye  310  via lens  302 . 
     In the example set forth in  FIG. 3 , there are two mirrors. Alternatively, there could be any number of mirrors each reflecting a portion of the illumination beam irradiated by the light source toward the eye. Each of the mirrors increases the divergence of the beam portion it reflects. 
     Reference is now made to  FIG. 4 , which is a schematic illustration of a surgical lens system, generally referenced  400 , constructed and operative in accordance with yet another embodiment of the disclosed technique.  FIG. 4 , depicts a cross section of surgical lens system  400  along a plane perpendicular to the optical axis of the lens. Lens system  400  includes a lens  402 , a mirror  404 , a light source  406 , a holder  408  and a fiber  410 . Holder  408  is mechanically connected to lens  402 . Mirror  404  and fiber  410  are incorporated into lens  402 . Light source  406  is incorporated into holder  408 . Mirror  404  is optically coupled with light source  406  via fiber  410 . Each of lens  402 , mirror  404  and light source  406  is substantially similar to lens  102 , mirror  104 , and light source  106 , of  FIG. 1 , respectively. 
     Holder  408  is employed for holding lens system  400 . That is, a user holds lens system  400  via holder  408  and positions lens  402  over the eye of a patient. Light source  406  is incorporated into holder  408  for reducing the size of lens system  400 . Additionally, by incorporating the light source into the holder, the light source is maintained mechanically connected to the lens, and thereby maintained optically aligned with the lens. In case lens  402  is a disposable lens, holder  408  (and incorporated light source  406 ) are either disposable as well, or are reused and coupled with a new lens for each subject. As opposed to the embodiments shown in  FIGS. 1 through 3 , light source  406  which is mechanically connected to the lens, can be positioned in any desired direction and is not limited to being positioned perpendicular to the FOV of the lens. 
     As can be seen in  FIG. 4 , mirror  404  is positioned off-axis (i.e., away from a center  412  of lens  402 ). It is noted though, that mirror  404  is located at the central region of lens  402  away from the periphery thereof. 
     In the examples set forth herein above the mirror incorporating lens of the disclosed technique was exemplified as a retinal surgical lens. However, the lens of the disclosed technique can be adapted to, and employed for, every scenario at which inspection of a darkened area (i.e., requiring illumination) is required, such as other body cavities as, for example, an ear of a subject. In particular, where zero-angle illumination is required, such as for dilated fundus examination or for Optical Coherence Tomography (OCT) applications. 
     It is noted that the retinal vision mechanism is common among vertebrates. Thus, the lens system of the disclosed technique can also be employed for retinal surgeries of non-human subjects, such as other mammals (e.g., horses or apes), or non-mammals vertebrates (e.g., reptiles or birds). 
     It will be appreciated by persons skilled in the art that the disclosed technique is not limited to what has been particularly shown and described hereinabove. Rather the scope of the disclosed technique is defined only by the claims, which follow.