Apparatus and method for reducing pukinje reflections and light fog associated with contact wide-angle real-time video output fundus imaging systems

Abstract

A contact eye imaging device includes a light source, a light transmitting structure optically coupled with the light source and positioned to emit light in a direction of an eye of a patient defining an illumination path, one or more optical lenses defining an imaging path, and a first polarizer positioned in the imaging path. The light emitted by the light transmitting structure may then be polarized, defining polarized illumination light. The first polarizer may be configured to at least partially cross-filter specularly reflected polarized illumination light from an eye of the patient.

Description

TECHNICAL FIELD

[0001] The present invention relates to a system and method for reducing the Purkinje reflections for a contact ophthalmic imaging system. BACKGROUND

[0002] The present invention relates to ophthalmoscopes, surgical microscopes, and other instruments used for internal observation and imaging of the human eye. More specifically, the present invention provides an illumination apparatus and system that includes a light filtering device for providing improved illumination efficiency over a large angular field of view while reducing Purkinje reflections for diagnostic and recording purposes of the human eye.

[0003] Past contact fundus cameras have used different methods to reduce Purkinje reflections. One method is to place a relatively large diameter circular light guide with a bell shaped angular power distribution behind the contact lens so that the illumination beam interacts with the intraocular lens interface outside or near the periphery of the imaging path where illumination is less. An example of this solution is presented in U.S. Patent No. 5,822,036. The problem with this approach is that the illumination is not uniform. In addition, the required pupil dilation can be larger than what is practically achievable for some infants.

[0004] Another method is to limit the angular field of view so that the Purkinje reflections are completely outside the imaging path at the intraocular interface, such as the ICON system from Phoenix Eye TM This is reflected in U.S. Patent No. 9,872,618. The problem associated with this approach is that the angular field of view can not be large enough for some retinopathy of prematurity (ROP) cases.

[0005] Yet another typical approach is to illuminate different regions of the retina sequentially and to digitally eliminate the Purkinje reflections by stitching together the portions of each sequentially obtained image that do not have Purkinje reflections from the multiple images captured sequentially so that the stitched image does not have Purkinje reflections. See, for example, U.S. Patent No. 10,743,764 and U.S. Patent Application Publication No. 2020 / 0163544. However, the disadvantage of this approach is that a higher frame rate is required, which can result in significant delays or inability to perform real-time video capture and / or display. In addition, the stitched frames can have undesirable patterns near the overlapping or border regions.

[0006] Although cross polarizer methods have been used in the past in fundus cameras, such as, for example, shown in U.S. Patent No. 7,275,826, these solutions are not suitable for contact fundus cameras with wide angular field of view and real-time video output. In addition, the '826 patent does not encourage the adoption of cross polarization methods.

[0007] Additional wide-angle lens solutions employ two unique methods of shaping the illumination beam to substantially improve illumination uniformity on the retina with a wide and uniform angular field of view, while requiring less pupil dilation than traditional ocular imaging systems, such as those shown in U.S. Patent Application Publication Nos. 2021 / 0106222 and 2021 / 0106223, the contents of each of which are incorporated by reference herein, unless the disclosure therein is inconsistent with the disclosure herein. In addition to wide-angle field of view and illumination uniformity, these two unique methods also reduce the Purkinje reflections by directing the intraocular lens reflected illumination beam more laterally, and thus further away from the imaging path. For many infant eyes, the Purkinje reflections and associated glare are not observed in the captured images. However, for very dark eyes and eyes with large anterior chamber depth, the Purkinje reflections and associated glare of the intraocular lens are still visible on the dark retina. The improvement of the present invention over the prior art is the application of the crossed polarizer method to a handheld contact wide-angle field of view real-time video output fundus imaging system with some specific configurations, resulting in high-quality captured video with reduced Purkinje reflections. SUMMARY

[0008] In view of the foregoing, embodiments of the present invention are directed to a contact ocular imaging device comprising a light source, a light transmission structure optically coupled with the light source and positioned to emit light in a direction of a patient’s eye along a defined illumination path, one or more optical lenses defining an imaging path, and a first polarizer positioned in the imaging path. The light emitted by the light transmission structure can then be polarized, defining polarized illumination light. The first polarizer can be configured to at least partially cross-filter specular reflections of the polarized illumination light from the patient’s eye.

[0009] In some embodiments, the contact ocular imaging device can further comprise a second polarizer positioned in the illumination path to produce the polarized illumination light. The second polarizer can be a ring-shaped ring positioned such that the imaging path passes through an aperture defined by the second polarizer. In some further embodiments, the contact ocular imaging device can further comprise a contact lens configured to interface with the patient’s eye and comprising an interface surface and a non-interface surface. The second polarizer can be positioned on the non-interface surface of the contact lens.

[0010] In some embodiments, the light transmission structure can comprise a plurality of polarized optical fibers configured to polarize the light emitted from the light transmission structure. In some embodiments, the first polarizer can be configured to rotate to change the cross-filtering polarization properties of the device.

[0011] In further embodiments, the contact eye imaging device can further include a fluorescence angiography filter. The device can be configured to switch between a first configuration in which the first polarizing optic is positioned in the imaging path and a second configuration in which the fluorescence angiography filter is positioned in the imaging path.

[0012] In some embodiments, the first polarizer can be at least one of a linear polarizer and a circular polarizer. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a side view of a contact eye imaging apparatus including a lens piece attached to a handpiece according to embodiments of the present application.

[0014] Figure 2 is a side cross-sectional view of a lens piece having an annular polarizing optical element according to embodiments of the present application.

[0015] Figure 3 is a side cross-sectional view of a lens piece having an annular polarizing contact lens.

[0016] Figure 4 is a side cross-sectional view of a lens piece having a polarizing optical fiber according to embodiments of the present application.

[0017] Figure 5 is a cross-sectional view showing an illumination path and an imaging path of an imaging system according to embodiments of the present application.

[0018] Figure 6 is a cross-sectional view showing an illumination path and an imaging path of an imaging system according to embodiments of the present application.

[0019] Figure 7a shows a reduction in a Purkinje reflection produced using a contact eye imaging apparatus according to embodiments of the present application.

[0020] Figure 7b shows a reduction in a Purkinje reflection produced using a contact eye imaging apparatus according to embodiments of the present application. DETAILED DESCRIPTION

[0021] The present application will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the application are shown. The application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art. One skilled in the art with access to the present disclosure will be able to devise further embodiments of the present application without departing from the scope of the present application. Skilled persons will understand that the description of the embodiments of the present application below is illustrative and is not intended to be limiting in any manner. Other embodiments of the present application will be readily apparent to such skilled persons having the benefit of this disclosure. Like numbers refer to like elements throughout.

[0022] While the following detailed description contains many specific details for the purpose of illustrating the application, any person of ordinary skill in the art will understand that many variations and alterations to the following details are within the scope of the present application. Accordingly, the following embodiments of the present application are set forth without any loss of generality to, and without imposing limitations upon, the application.

[0023] In this detailed description of the application, those skilled in the art should note that directional terms, such as "above," "below," "upper," "lower," and other like terms are used for ease of describing the accompanying drawings. Also, those skilled in the art should note that the description can contain other terminology that describes the positional, orientational, and directional relationships between objects, elements, and acts. It is noted that "light" can be referred to differently herein as "illumination," "illumination beam," "visual wavelength," "color," and the like.

[0024] Further, in this detailed description of the application, those skilled in the art should note that quantitative limiting terms such as "generally," "substantially," "mostly," and the like are generally used to indicate that the referenced object, property, or quality constitutes a majority of the reference subject. The meaning of any of these terms depends on the context in which it is used, and the meaning can be explicitly modified.

[0025] As shown and described in the various figures and accompanying text, embodiments of the present application provide a handheld contact imaging device 100 for the eye. The contact imaging device 100 for the eye can be configured to interface with the cornea of a patient's eye to provide real-time wide-angle fundus imaging and video capture. The contact imaging device 100 for the eye can include a lens piece 110 that is attached to a handheld piece 120. The lens piece 110 can be removably attached to the handheld piece 120, thereby allowing a variety of lens pieces to be attached to the handheld piece 120. The handheld piece 120 can include a light emitting device. When attached, the lens piece 110 can be positioned in optical communication with the handheld piece 120 such that light generated by the light emitting device of the handheld piece 120 can pass along an illumination path of the lens piece 110, and light can propagate along an imaging path of the lens piece 110 to the handheld piece 120. The handheld piece 120 can further include an imaging device operable to collect and measure light received from the lens piece 110 and generate a real-time video signal from the light.

[0026] Reference is now made to Figure 2A side cross-sectional view of a lens piece 200 according to embodiments of the present application is presented. The lens piece 200 includes a housing 202, a light transport structure 210, a contact lens 230, and a polarizer 220. The light transport structure 210 can be configured to receive light from a light emitting device of the handheld piece 120 at a first end 212 to allow the received light to propagate through a length 214 of the light transport structure 210 and be emitted from a second end 216 thereof. The light transport structure 210 can include one or more structures operable to receive, transport, and emit light as described, including but not limited to optical waveguides such as optical fibers, transparent dielectric waveguides made of plastic or glass, light pipes, and the like. Although two light transport structures 210 are seen in Figure 2

[0027] Light can be emitted from the second end 216 of the light transport structure 210 and propagate along an illumination path 206 into the patient’s eye 204. In some embodiments, the lens piece 200 can include an illumination path polarizer 220 positioned between the second end 216 of the light transport structure 210 and the patient’s eye 204. In some embodiments, the illumination path polarizer 220 can be positioned intermediate the second end 216 of the light transport structure 210 and a contact lens 230 of the lens piece 200 that is configured to interface with the patient’s eye 204. Positioning the illumination path polarizer 220 in this location can polarize a greater portion of the light emitted from the light transport structure 210, thereby efficiently polarizing the light required for retinal imaging. The illumination path polarizer 220 can be a discrete structure positioned proximate the second end 216 of the light transport structure 210 and the contact lens 230, but in some embodiments, can be manipulatable and replaceable independent of the light transport structure 210 and the contact lens 230.

[0028] The contact lens 230 can be substantially transparent, thereby allowing all light of any polarization to pass therethrough. Further, in some embodiments, the contact lens 230 can avoid any absorption, reflection, or refraction of light passing therethrough, thereby avoiding imparting any change to the optical properties of the light passing therethrough.

[0029] ​The shape of the illumination path polarizer 220 can mirror the configuration of the light transport structure 210. In the present embodiment, where the light transport structure comprises a plurality of structures arranged such that their second ends 216 define an annular array, the shape of the illumination path polarizer 220 can be annular. In a similar embodiment, where the light transport structure 210 is an annular light guide, the shape of the illumination path polarizer 220 can likewise be annular.

[0030] The annular illumination path polarizer 220 can allow light passing through the illumination path polarizer to be polarized, while allowing light reflected from the patient’s eye 204 to pass along the imaging path through the aperture 222 defined by the illumination path polarizer, as will be discussed in greater detail below. However, it is contemplated and included within the scope of the present application that the illumination path polarizer 220 can take any shape, such shape conforming or not conforming to the shape of the second ends 216 of the light transport structure 210.

[0031] The polarization of the illumination path polarizer 220 can be linear or circular / elliptical. Where the illumination path polarizer 220 is a linear polarizer, the plane of polarized light passing therethrough can be changed by rotating the illumination path polarizer 220. In some embodiments, an operator can manipulate the illumination path polarizer 220 to rotate the illumination path polarizer 220 before, during, or after operation of the ocular imaging device 100. Such manipulation can change the cross-polarization of the imaging path polarizer, as will be described below.

[0032] Polarized light from the illumination path polarizer, defined as polarized illumination light, can be reflected by the patient’s eye 204 along the imaging path and through the aperture 222, as described above. Such light can be specularly reflected from the anterior and / or posterior interfaces of the intraocular lens. The lens piece 200 can further comprise one or more imaging path optical lenses 240 in addition to the contact lens, the central region of which also acts as one of the imaging path lenses. The imaging path optical lenses 240 can be configured to change the optical properties of the light reflected from the patient’s eye 204. Further details regarding the imaging path optical lenses can be found in the above-referenced U.S. Patent Application Publication Nos. 2021 / 0106222 and 2021 / 0106223.

[0033] The lens piece 200 can further include an imaging path polarizer 250. The imaging path polarizer 250 can be configured to at least partially cross-filter light reflected from the patient's eye 204. The reflected light can be specularly reflected from the patient's eye. Further, the reflected light can have been polarized, for example, by the illumination path polarizer 220. The polarization direction of the imaging path polarizer 250 can be oriented such that, in the case of linear polarization, the planes defining the polarizations of the polarizers 220, 250 are non-parallel, i.e., form an angle defined as the relative orientation angle. In some embodiments, the relative orientation angle can be in the range of 0 degrees to 180 degrees, in the range of greater than 0 degrees to less than 180 degrees, and permutations thereof. The imaging path polarizer 250 can be configured to maintain the fidelity of the anatomical features of the patient's eye 204 shown in the image represented by the light in the imaging path after cross-polarizing the reflected light, while mitigating the presence of Purkinje reflections in the reflected light.

[0034] In some embodiments, the imaging path polarizer 250 can be configured to further define an optical protection window such that the internal structure of the lens piece 200 can be protected from environmental contaminants by the imaging path polarizer 250. Additionally, in some embodiments, the imaging path polarizer 250 can be configured to be manipulatable by a user to change the polarization orientation angle relative to the illumination path polarizer 220, as described above. For example, the imaging path polarizer can be configured to rotate relative to the illumination path polarizer 220, thereby changing the relative orientation angle.

[0035] Referring now to Figure 3 , a lens piece 300 according to embodiments of the present application is presented. The lens piece 300 can include a light transport structure 310 and a contact lens 330, as described above. Additionally, the contact lens 330 can include an interface surface 332 configured to interface with a patient's eye 304 and a non-interface surface 334 generally opposite the interface surface 322. In the present embodiment, the illumination path polarizer 320 can be deposited on the non-interface surface 324 of the contact lens 330. Such deposition can be achieved by any means or method known in the art. In some embodiments, the illumination path polarizer 320 can be a thin film adhered to the non-interface surface 324 by any means or method known in the art.

[0036] Referring now to Figure 4 , a lens piece 400 according to embodiments of the present application is presented. In the present embodiment, the light transport structure 410 is configured to polarize light emitted from the second end 416. This eliminates the need for a discrete illumination path polarizer. Such polarization can occur at any point along the light transport structure, including at the first end 412, along the length 414, or at the second end 416.

[0037] Referring now to Figure 5FIG. 5 shows an illumination path and an imaging path of an imaging system according to embodiments of the present application. Ocular imaging device 500 includes light source 502, handpiece 510, and lens piece 520. Light source 502 can be any device operable to produce light in the range of the ocular imaging spectrum, such as the visible spectrum necessary to perform ocular imaging, including but not limited to light emitting diodes (LEDs), organic LEDs, incandescent light illumination devices, halogen light illumination devices, fluorescent light illumination devices, and the like. Light source 502 can be located inside or outside the housing of handpiece 510.

[0038] Handpiece 510 can include image sensor 512. Image sensor 512 can be configured to connect to a real-time video display (not shown) to present to a user a video depiction of the light received at image sensor 512 in imaging path 511. Any type of image sensor known in the art is contemplated and included within the scope of the present application, including but not limited to charge-coupled devices (CCDs), CMOS devices, NMOS devices, hybrids thereof, and the like. Handpiece 510 can further include a dichroic prism block or optical path length compensation block 513 optically positioned in front of image sensor 512 along imaging path 511. Handpiece 510 can further include a deep red and / or near infrared cut filter 514 optically positioned in front of block 513 along imaging path 511. Handpiece 510 can further include an axially movable lens combination 515 optically positioned in front of filter 514 along imaging path 511. Details regarding the axially movable lens combination are presented in the above-referenced U.S. Patent Application Publication Nos. 2021 / 0106222 and 2021 / 0106223.

[0039] Handpiece 510 can further include imaging path selectable device 516. Imaging path selectable device 516 can be configured to be manipulated by a user to position device 516 in one of at least two orientations to selectively position one of at least two optical elements in imaging path 511. The first optical element can be imaging path cross-polarizer 517, as described above, which can be positioned in imaging path 511 when device 516 is in a first orientation. With this imaging path polarizer 517 in the handpiece, it can no longer be necessary to have a polarizer in the lens piece, as described above. Figure 2The previously described imaging path polarizer 250 is shown. The second optical element can be a bandpass filter 518 configured to allow light within a range of wavelengths to pass through, which can be positioned in the imaging path 511 when the device 516 is in the second orientation. In this embodiment, the bandpass filter 518 can be configured to allow light within the green wavelength range, for example light having a peak wavelength in the range of 490 nm to 570 nm. Such a range can be advantageous for the performance of fluorescent angiography. This range is exemplary only, and any range is contemplated and included within the scope of the present application. Further, the device 516 can include multiple bandpass filters, each having a different range of wavelengths allowed to pass therethrough.

[0040] The handpiece 510 can further include a handpiece light transport structure 519 configured to optically couple with each of the light source 502 and the light transport structure 522 of the lens piece 520 and transport light from the light source 502 to the light transport structure 522.

[0041] Reference is now made to Figure 6 , presenting a cross-sectional view of an ocular imaging device 600 according to an embodiment of the present application. The ocular imaging device 600 can be substantially similar to the ocular imaging device 500 of Figure 5 , except for the imaging path selectable device 516. In this embodiment, the ocular imaging device 600 includes a handpiece 610 including an imaging path polarizer 612 positioned in the imaging path 611. The imaging path polarizer 612 can be configured to be rotated by a user to change the relative orientation angle between the imaging path polarizer and the illumination path polarizer 622 of the lens piece 620 of the ocular imaging system 600, as described above. In such embodiments, the imaging path polarizer 612 can be a linear polarizer.

[0042] Reference is now made to Figures 7a to 7b , presenting imaging of a patient ocular model 700 using the application described above. Figure 7a A patient ocular model 700' is shown without the cross-polarization described in the embodiments of the application described above, in which the prominent Purkinje reflections 702' are very clearly visible and obscure a greater portion of the anatomy of the patient ocular 700'. Figure 7b The same patient ocular model 700" is shown with the cross-polarization described above, in which the Purkinje reflections 702" are greatly reduced, making the previously obscured anatomy more clearly visible.

[0043] Some illustrative aspects of the present application can be advantageous in addressing the problems described herein as well as other, unaddressed problems that can be discovered by those skilled in the art.

[0044] While the above description includes many specificities, it will be understood by those skilled in the art that these are included for the purpose of providing a detailed example of the present embodiments and should not be understood as a limitation on the scope of any embodiments. Many other derivations and changes are possible within the teachings of the various embodiments. While the present application has been described with reference to example embodiments, it will be understood by those skilled in the art that various changes can be made and equivalents can be substituted for elements of the example embodiments without departing from the scope of the present application. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the present application without departing from the central scope of the application. Accordingly, it is intended that the present application not be limited to the specific embodiments disclosed as the best mode contemplated for carrying out this application, but rather that the application be included within the scope of the description of the present application. Also, the example embodiments of the present application have been disclosed with reference to the accompanying drawings and description herein, although specific terminology has been employed, such terminology is used in a generic and descriptive sense only and not for purposes of limitation, and therefore the scope of the present application is not limited to the specific embodiments disclosed herein. Furthermore, the use of the terms "first", "second", etc. do not imply any order or importance, but are used to distinguish one element from another, and the use of the terms one, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

Claims

1. A contact ocular imaging device, comprising: a light source; a light transport structure optically coupled with the light source and positioned to emit light in a direction of a patient's eye defining an illumination path; one or more optical lenses defining an imaging path; and a first polarizer positioned in the imaging path; wherein the light emitted by the light transport structure is subsequently polarized, defining polarized illumination light; and wherein the first polarizer is configured to at least partially cross-filter polarized illumination light from specular reflections from the patient's eye.

2. The contact ocular imaging device of claim 1, further comprising a second polarizer positioned in the illumination path to produce the polarized illumination light.

3. The contact ocular imaging device of claim 2, wherein the second polarizer is an annular ring positioned such that the imaging path passes through an aperture defined by the second polarizer.

4. The contact ocular imaging device of claim 2, further comprising a contact lens configured to interface with the patient's eye and comprising an interface surface and a non- interface surface; wherein the second polarizer is positioned on the non-interface surface of the contact lens.

5. The contact ocular imaging device of claim 1, wherein the light transport structure comprises a plurality of polarized optical fibers configured to polarize light emitted from the light transport structure.

6. The contact ocular imaging device of one of claims 1-5, wherein the first polarizer is configured to rotate to change a cross-filtering polarization characteristic of the device.

7. The contact ocular imaging device of one of claims 1-6, further comprising a fluorescence angiography filter; wherein the device is configured to switch between a first configuration in which the first polarizing optic is positioned in the imaging path and a second configuration in which the fluorescence angiography filter is positioned in the imaging path.

8. The contact ocular imaging device of one of claims 1-7, wherein the first polarizer is at least one of a linear polarizer and a circular polarizer.

9. A contact ocular imaging device, comprising: a light source; a light transport structure optically coupled with the light source and positioned to emit light in a direction of a patient's eye defining an illumination path; one or more optical lenses defining an imaging path; a first polarizer being at least one of a linear polarizer and a circular polarizer and positioned in the imaging path; and a second polarizer positioned in the illumination path to polarize light emitted by the light transport structure to produce polarized illumination light; wherein the first polarizer is configured to at least partially cross-filter polarized illumination light from specular reflections from the patient's eye. ​ ​ 10. The contact ocular imaging device of one of claims 9, wherein the second polarizer is an annular ring positioned such that the imaging path passes through an aperture defined by the second polarizer.

11. The contact ocular imaging device of claim 10, further comprising a contact lens configured to interface with the patient eye and comprising an interface surface and a non-interface surface; wherein the second polarizer is positioned on the non-interface surface of the contact lens.

12. The contact ocular imaging device of claims 9-11, wherein the first polarizer is configured to rotate to change a cross-filtering polarization characteristic of the device.

13. The contact ocular imaging device of one of claims 9-12, further comprising a fluorescein angiography filter; wherein the device is configured to switch between a first configuration in which the first polarizing optics are positioned in the imaging path and a second configuration in which the fluorescein angiography filter is positioned in the imaging path.

14. A contact ocular imaging device, comprising: a light source; a light transport structure optically coupled with the light source, comprising a plurality of polarizing optical fibers, and positioned to emit polarized illumination light in a patient eye direction defining an illumination path; one or more optical lenses defining an imaging path; and a first polarizer positioned in the imaging path; wherein the first polarizer is configured to at least partially cross-filter polarized illumination light from a specular reflection from the patient eye.

15. The contact ocular imaging device of claim 14, wherein the first polarizer is configured to rotate to change a cross-filtering polarization characteristic of the device.

16. The contact ocular imaging device of one of claims 14-15, further comprising a fluorescein angiography filter; wherein the device is configured to switch between a first configuration in which the first polarizing optics are positioned in the imaging path and a second configuration in which the fluorescein angiography filter is positioned in the imaging path.

17. The contact ocular imaging device of one of claims 14-16, wherein the first polarizer is at least one of a linear polarizer and a circular polarizer. ​

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