WO2018201008A1

WO2018201008A1 - Non-mydriatic mobile retinal imager

Info

Publication number: WO2018201008A1
Application number: PCT/US2018/029886
Authority: WO
Inventors: Aadit SHAH; Sachin P. KALARN
Original assignee: Spect Inc
Current assignee: Spect Inc
Priority date: 2017-04-28
Filing date: 2018-04-27
Publication date: 2018-11-01
Anticipated expiration: 2019-10-28

Abstract

Disclosed herein are devices and methods for acquiring non-mydriatic images of the fundus of the eye (e.g., retina, optic disc, macula, fovea, and posterior pole). One variation of an imaging system may comprise an optical lens assembly, a first light source (e.g., a red and/or near-infrared light source), a light emitter, and control circuity comprising a light-dependent resistor that is configured to control activation of the first light source according to light output from the light emitter. The light emitter may comprise a fiber optic cable that optically connects the visible light source of the portable computing device (e.g., its flash light source) with the control circuitry.

Description

NON-MYDRIATIC MOBILE RETINAL IMAGER

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Patent Application No. 62/491,597, filed April 28, 2017, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

[0002] Regular and accessible eye screening can help promote early detection of optical diseases such as retinopathy and glaucoma, and help prevent those diseases from progressing further and leading to blindness. However, eye screening often involves expensive and bulky equipment that are typically limited to use in a physician's office. Access to physicians who have specialized equipment for eye screening and expertise in diagnosing ophthalmological diseases may be a major challenge for individuals who live in rural areas and/or regions where there are few (if any) eye care specialists. This may lead to delays in medical care for preventable and irreversible causes of blindness.

[0003] Furthermore, in order to obtain good quality images of the fundus of the eye (e.g., retina, optic disc, macula, fovea, and posterior pole), eye care specialists commonly induce dilation of the pupil by administering a mydriatic agent. However, because mydriatic agents can cause pupil dilation that lasts hours after the eye screening session, individuals often find it inconvenient and even disruptive to their normally scheduled activities, and are therefore deterred from regular and/or frequent screening. While imaging of the retina and/or fundus region is possible without pupil dilation, the images often have a reduced field-of-view as compared to images acquired with pupil dilation.

[0004] Accordingly, it is desirable to develop simple, inexpensive, and portable eye screening equipment that can acquire images of the retina and/or fundus region of the eye with a sufficiently wide field-of-view without the use of a mydriatic agent. SUMMARY

[0005] Disclosed herein are devices and methods for acquiring non-mydriatic images of the fundus of the eye (e.g., retina, optic disc, macula, fovea, and posterior pole). One variation of a device for acquiring non-mydriatic images comprises a detachable imaging system that is configured to be coupled to a portable computing device that has an image sensor and visible light source (e.g., white light), such as a smartphone or tablet. The detachable imaging system may illuminate an individual's eye(s) with red and/or near-infrared light (e.g., light having wavelengths from about 570 nm to about 1200 nm) to encourage pupil dilation and to allow a clinician or technician to adjust the field-of-view and focus of the imaging system. At the moment of (and optionally, just prior to) image capture by the portable computing device image sensor, the eye may be rapidly and briefly illuminated with white light from the portable computing device, before the pupil constricts. One variation of a detachable imaging system may comprise an optical lens assembly, a first light source (e.g., a red and/or near-infrared light source), a light emitter, and control circuity that is configured to control activation of the first light source according to light output from the light emitter. The light emitter may comprise a fiber optic cable that optically connects the visible light source of the portable computing device (e.g., its flash light source) with the control circuitry. Before an image is acquired (i.e., the light source of the portable computing device is not activated), the first light source illuminates the eye with red and/or near-infrared light. When the clinician or technician decides to acquire an image, the light source of the mobile device may be activated and its light may travel through the fiber optic cable to the control circuitry and cause deactivation of the red and/or near-infrared light provided first light source. The visible light from the fiber optic cable may also be used to briefly illuminate the eye as an image is acquired by the mobile device image sensor. The duration of the visible light may be brief, for example, from about 0.001 second to about 1 second (e.g., about 0.01 second, about 0.5 second) such that an image may be acquired before the pupil substantially constricts in response to the visible light.

[0006] In one variation, the control circuitry may comprise a light-dependent circuit component such as a light-dependent resistor and/or a photodiode positioned adjacent to the fiber optic cable and configured to control activation of the first light source by changing a resistance of the light-dependent resistor according to the light output from the fiber optic cable and/or mobile device visible light source. For example, the first light source may be a light- emitting diode (LED) and illumination of the light-dependent resistor (i.e., by the flash light source of the mobile device via the fiber optic cable) may cause a decrease in resistance value which may reduce or eliminate the current flow (i.e., power supply) to the LED, and shut the LED off. The eye may then be illuminated with the light from visible/white light (instead of red and/or infrared light) for image acquisition. When the light-dependent resistor is no longer illuminated (i.e., the flash light source of the mobile device is off), its resistance value may increase and drive current flow (i.e., power supply) to the LED such that red and/or near-infrared illumination is provided to the eye.

[0007] Also disclosed herein are methods for acquiring non-mydriatic images of the fundus of the eye. One variation of a method comprises illuminating a patient's eye with a near-infrared light source of a detachable imaging system coupled to a portable computing device, activating the visible light source of the portable computing device to deactivate the near-infrared light source, illuminating the patient's eye with the visible light source of the portable computing device, and acquiring an image of the patient's eye using the image sensor of the portable computing device. The detachable imaging system may further comprise control circuitry comprising a light-dependent resistor that controls activation of the near-infrared light source according to light output from the visible light source of the portable computing device, and activating the visible light source of the portable computing device may change a resistance of the light-sensitive (i.e., light-dependent resistor), causing deactivation of the near-infrared light source.

[0008] One variation of an imaging system (e.g., a detachable imaging system) for acquiring non-mydriatic images of an eye using a portable computing device may comprise an optical lens assembly, a light emitter optically connected to the optical lens assembly to provide illumination to the optical lens assembly, a first light source optically connected to the optical lens assembly, and control circuitry in electrical communication with the first light source. The control circuitry may comprise a light-dependent resistor positioned adjacent to the light emitter and configured to control activation of the first light source by changing a resistance value of the light- dependent resistor according to light output from the light emitter. The light emitter may comprise a light guide such as a fiber optic cable that may be configured to optically connect a second light source with the optical lens assembly. The second light source may comprise a light source of a portable computing device. The light emitter may emit visible wavelength light, and/or the light source of the portable computing device may emit visible wavelength light. The first light source may emit near-infrared or red wavelength light and may comprise, for example, a light-emitting diode. In some variations, when the light output from the light emitter is at or below a pre-determined illumination threshold, the resistance value of the light-dependent resistor may increase and cause activation of the first light source. Additionally, when the light output from the light emitter increases above the pre-determined illumination threshold, the resistance value of the light-dependent resistor may decrease and cause deactivation of the first light source. In some variations, the system may further comprise a first beam splitter in optical connection with the light emitter and the first light source, and the first beam splitter may have a transmission to reflectance ratio of at least about 60:40 such that a greater proportion of light from the light emitter is transmitted to the optical lens assembly than is reflected from the first light source to the optical lens assembly.

[0009] Some variations of a system for non-mydriatic imaging may further comprise an optical lens assembly housing that encloses the optical lens assembly, and a portable computing device case configured to releasably couple to a portable computing device. The light emitter, first light source, and control circuitry may be mounted to the portable computing device case, and the optical lens assembly housing may be configured to be releasably attached to the portable computing device case. The light emitter may comprise a fiber optic cable comprising a first end and a second end, and the portable computing device case may comprise a first optically-opaque enclosure disposed over the first end of the cable and a second optically- opaque enclosure disposed over the second end of the cable. In some variations, the optical lens assembly may comprise a collector lens configured to receive light from the light emitter and the first light source, a first polarizing filter configured to transmit light from the collector lens having a first orientation, a second beam splitter that is configured to reflect light from the first polarizing filter having the first orientation and configured to transmit light having a second orientation that is opposite to the first orientation, an objective lens, a second polarizing filter configured to transmit light from the objective lens having the second orientation, and a relay lens that transmits light from the second polarizing filter to an image sensor of a portable computing device. In some variations, the objective lens may be retained within an objective lens mount, and the optical lens assembly housing may comprise an attachment region with a plurality of threaded protrusions, and the objective lens mount may comprise a receiving region with a plurality of threaded grooves that correspond with the threaded protrusions.

[0010] An optical lens assembly may be configured to provide illumination light with along an illumination axis to an illumination focal point in an eye, and to receive light along an imaging axis, and where the illumination axis is offset from the imaging axis. For example, the second beam splitter may have a first central axis and the relay lens may have a second central axis, and the first central axis may be offset from the second central axis (e.g., the first central axis may be offset by about 1.25 mm from the second central axis).

[0011] Also disclosed herein are methods for acquiring non-mydriatic images of the eye. One variation of a method for acquiring non-mydriatic images of an eye using a portable computing device (e.g., a smartphone) may comprise illuminating a patient's eye with a near-infrared light source of an imaging system coupled to a portable computing device that comprises a visible light source and an image sensor, activating the visible light source of the portable computing device, illuminating the patient's eye with the visible light source of the portable computing device and deactivating the near-infrared light source, and acquiring an image of the patient's eye using the image sensor of the portable computing device. The imaging system may comprises control circuitry comprising a light-dependent resistor that controls activation of the near-infrared light source according to light output from the visible light source of the portable computing device, and activating the visible light source of the portable computing device may change a resistance value of the light-dependent resistor and deactivate the near-infrared light source. In some variations, the imaging system may further comprise a fiber optic cable that optically connects the visible light source of the portable computing device and the light- dependent resistor such that light from the visible light source may illuminate the light- dependent resistor. The imaging system may further comprise an optical lens assembly comprising a collector lens configured to receive light from the fiber optic cable and the near- infrared light source, a first polarizing filter configured to transmit light from the collector lens having a first orientation, a second beam splitter that is configured to reflect light from the first polarizing filter having the first orientation and configured to transmit light having a second orientation that is opposite to the first orientation, an objective lens, a second polarizing filter configured to transmit light from the objective lens having the second orientation, and a relay lens that transmits light from the second polarizing filter to the image sensor of the portable computing device. The method may further comprise adjusting an optical path length between the obj ective lens and the relay lens, which may help mitigate patient refractive errors before illuminating the patient's eye with the visible light source of the portable computing device. In some variations, illuminating the patient's eye with the visible light source of the portable computing device may comprise illuminating the patient's eye with visible wavelength light for less than about 0.5 second. The visible wavelength light may comprise white light. Activating the visible light source may comprise increasing light output from the fiber optic cable above a pre-determined illumination threshold which may cause the resistance value of the light- dependent resistor to decrease and deactivate the near-infrared light source. Additionally, when the light output from the fiber optic cable is at or below the pre-determined illumination threshold, the resistance value of the light-dependent resistor may increase and activate the near- infrared light source.

[0012] In some variations, illuminating the patient's eye may comprise providing illumination light with along an illumination axis to an illumination focal point in the eye, and acquiring an image of the patient's eye comprises receiving light by the image sensor along an imaging axis, where the illumination axis is offset from the imaging axis. For example, the illumination axis may be offset from the imaging axis by about 1.25 mm. Optionally, some variations may comprise disposing a pair of glasses over the patient's eyes prior to acquiring an image of their eyes. The glasses may comprise color-tinted filtered lenses that transmit light having a wavelength longer than about 580 nm, and frames that retain the lenses. The frames may comprise one or more side, top, and/or bottom light-blocking flaps to simulate a low-light environment for the patient.

[0013] Also described herein are kits for acquiring non-mydriatic images of an eye. One variation of a kit may comprise a portable computing device comprising a camera having an image sensor and a visible light source, and an imaging device configured to be coupled to the portable computing device, the imaging device comprising an optical lens assembly, a near- infrared light source that is optically connected to the optical lens assembly, and a control circuit that is electrically connected to the near-infrared light source and optically connected to the portable computing device image sensor. The control circuit may comprise a light-dependent resistor and the detachable imaging device may further comprise a fiber optic cable having a first light-receiving portion optically connected to the portable computing device visible light source and an illumination portion adjacent to the light-dependent resistor. The near-infrared light source may be connected to the control circuit such that activation of the near-infrared light source may be controlled by changing a resistance value of the light-dependent resistor according to light output from the illumination portion of the fiber optic cable. A kit may optionally comprise a pair of glasses comprising color-tinted filtered lenses that selectively transmits light having a wavelength longer than about 580 nm and frames that retain the lenses, where the frames may comprise one or more side, top, and/or bottom light-blocking flaps.

Optionally, a kit may further comprise a fluorescence imaging device configured to be coupled to the portable computing device, where the fluorescence imaging device may comprise an optical lens assembly, an ultraviolet light source that is optically connected to the optical lens assembly, and a control circuit that is electrically connected to the ultraviolet light source and optically connected to the portable computing device image sensor. Optionally, a kit may further comprise a fluorescence imaging device configured to be coupled to the portable computing device, where the fluorescence imaging device may comprise an optical lens assembly, a blue or green light source that is optically connected to the optical lens assembly, and a control circuit that is electrically connected to the blue or green light source and optically connected to the portable computing device image sensor. Any of the imaging devices of a kit may be configured to be detachably coupled to the portable computing device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 A depicts a perspective view of one variation of a system for acquiring non- mydriatic images of the eye. FIG. IB is a front view of the system of FIG. 1A.

[0015] FIG. 2A is a perspective view of one variation of an optical lens assembly. FIG. 2B is a side view of the optical lens assembly of FIG. 2A. FIG. 2C is a partial exploded side view of the optical lens assembly of FIG. 2A. FIG. 2D depicts a partial cutaway side view and a front view of one variation of an optical lens assembly. [0016] FIG. 3A is a front view of one variation of an objective lens and objective lens mount. FIG. 3B is a perspective front view of the objective lens and objective lens mount of FIG. 3 A.

[0017] FIG. 4A is a perspective cutaway view of one variation of an optical lens assembly housing. FIG. 4B is a perspective view of an optical lens assembly and a portion of a portable computing device case.

[0018] FIG. 5 is a schematic depiction of the focal points and axes of the illumination light and the imaging light.

[0019] FIG. 6 A is an elevated perspective view of one variation of a portable computing device case of an imaging system for acquiring non-mydriatic images of the eye. FIG. 6B is a front view of the portable computing device case of FIG. 6A. FIG. 6C is a close-up elevated perspective view of the portable computing device case of FIG. 6A. FIG. 6D is a partial cutaway front view of the portable computing device case of FIG. 6A. FIG. 6E is a side perspective view of the portable computing device case of FIG. 6A with a shell or housing for enclosing components of the portable computing device case.

[0020] FIG. 7 is a circuit diagram of one variation of a control circuit.

[0021] FIG. 8A is a front view of one variation of an imaging system for acquiring non- mydriatic images of the eye. FIG. 8B is a close-up perspective view of one variation of a detachable optical lens assembly interface with one variation of a portable computing device case.

[0022] FIG. 9A depicts one variation of a pair of glasses for use in a method for non-mydriatic imaging of the eye. FIG. 9B is a flowchart representation of one method for acquiring images of the eye.

DETAILED DESCRIPTION

[0023] Disclosed herein are devices and methods for acquiring non-mydriatic images of the fundus of the eye (e.g., retina, optic disc, macula, fovea, and posterior pole). One variation of a system for acquiring non-mydriatic images comprises a portable computing device that has an image sensor and visible light source (e.g., white light), such as a smartphone or tablet, and a detachable imaging system that is configured to be coupled to the portable computing device. The detachable imaging system may illuminate an individual's eye(s) with red and/or near- infrared to encourage pupil dilation and to allow a clinician or technician to adjust the field-of- view and focus of the imaging system. At the moment of (and optionally, just prior to) image capture by the portable computing device image sensor, the eye may be rapidly and briefly illuminated with white light from the portable computing device, before the pupil constricts. Rapid and brief exposure to white light may allow for the acquisition of fundus images through a non-pharmacologically dilated pupil (i.e., without the administration of a mydriatic agent). The acquired image(s) may be stored in a memory of the portable computing device.

[0024] Also disclosed herein are methods for acquiring non-mydriatic images of the fundus of the eye. One variation of a method comprises illuminating a patient's eye with a near-infrared light source of a detachable imaging system coupled to a portable computing device, activating the visible light source of the portable computing device to deactivate the near-infrared light source, illuminating the patient's eye with the visible light source of the portable computing device, and acquiring an image of the patient's eye using the image sensor of the portable computing device. The detachable imaging system may further comprise control circuitry comprising a light-dependent resistor that controls activation of the near-infrared light source according to light output from the visible light source of the portable computing device, and activating the visible light source of the portable computing device may change a resistance of the light-sensitive (e.g., light-dependent) resistor, causing deactivation of the near-infrared light source.

[0025] Since portable computing devices are widespread and generally available, a detachable imaging system such as any of those described below may provide the additional optical functions that facilitate the acquisition of eye images, thereby helping to improve access to eye screening. Furthermore, the ability to acquire fundus images without a mydriatic agent may help remove at least one barrier to regular and/or frequent fundus screening. In addition, images acquired using the device and methods described herein may be electronically transmitted to remote eye care specialists for analysis and/or diagnosis. That is, even if individuals do not have access to the expertise of a local eye care specialist, they are able to seek and obtain medical advice from a remote specialist, which may help expedite the commencement and progress of treatment.

[0026] While the examples described and depicted below use a smartphone for the acquisition and processing of fundus images, it should be understood that the devices and methods described herein may be adapted for use with any portable computing device comprising an image sensor and visible light source (i.e., flash) to acquire images of any portion of the eye. For example, the devices and methods described herein may be used with any type of portable computing devices include smartphones, personal digital assistants (PDAs), cell phones, tablet PCs, phablets (personal computing devices that are larger than a smartphone, but smaller than a tablet) and the like, and portable or wearable augmented reality devices that interface with an operator's environment through sensors and may use head-mounted displays for visualization, eye gaze tracking, and user input. Light and/or image data detected by the portable computing device image sensor may be displayed in a view finder and/or preview frame of a portable computing device camera application. When a particular image view and/or light data and/or image data is to be saved, the user may trigger the camera to acquire the image by, for example, pressing a button, key, and/or graphic on a touch-sensitive screen of the portable computing device.

Alternatively or additionally, the camera may be triggered to acquire an image by pressing a button or key located on an external housing of the portable computing device. In some variations, image acquisition may be triggered by an auto-capture algorithm, which may be stored in a memory of the portable computing device and executed by a controller of the portable computing device. One variation of an auto-capture mode may comprise detecting a pre-defined event or pre-defined pattern of events, and triggering the camera to acquire one or more images when the pre-defined event or pattern of events is detected. For example, in auto- capture mode, the camera may be triggered to acquire an image when it detects that the images in the preview frame is in focus, and/or when features of interest (e.g., optic nerve, fundus, etc.) are within the field-of-view of the camera. Additionally or alternatively, the camera of the portable computing device variations may capture moving images or video. For example, to capture moving images (e.g., a series of still images) and/or video of a fundus through a dilated pupil (e.g., dilated without mydriatic agents or dilated with mydriatic agents), the visible light source of the portable computing device (flash) may be pulsed repeatedly with several second- long intervals between each flash. This may allow video capture of the fundus while maintaining pupil dilation and/or limiting pupil constriction (due to the visible light pulse). For example, the visible light pulses may be from about 0.01 second to about 1 second in duration, and the inter- pulse interval may be from about 5 seconds to about 10 seconds. In some variations, a series of still images may be acquired where each image is acquired simultaneously with each light pulse. The devices and methods described herein may be used to acquire images of the retina

(including the macula), and/or optic nerve, and/or cornea, and/or anterior and/or posterior chamber, and/or lens, and/or pupil, and/or vitreous body.

Devices

[0027] FIGS. 1A and IB depict one variation of a detachable imaging system for acquiring non-mydriatic images of an eye (e.g., fundus images). The system (100) may comprise an optical lens assembly (102), a first light source (104) optically connected to the optical lens assembly, and control circuitry (106) configured to control activation of the first light source (104). The detachable imaging system (100) may comprise a light emitter or light guide (110) optically connected to the optical lens assembly (102) (when it is attached to the case) and also optically connected to the control circuitry (106) so that the first light source (104) may be activated according to light output from the light emitter (110). The first light source (104) may be a red and/or near-infrared (NIR) light source that provides illumination (e.g., from about 580 nm to about 1200 nm, about 530 nm to about 650 nm, about 680 nm to about 750 nm) to encourage dilation of the pupil. In some variations, the first light source may emit light having other wavelengths, for example, light having wavelengths from about 100 nm to about 400 nm (UV light), and/or light having wavelengths from about 450 nm to about 500 nm (blue light), and/or light having wavelengths from about 500 nm to about 570 nm (green light), etc. The detachable imaging system (100) may be configured to be coupled to a portable computing device (108) comprising a camera lens (109) disposed over an image sensor and a light source

(111) (e.g., flash). The portable computing device may be a smartphone, for example. In one variation, the optical lens assembly (102) may be enclosed in an optical lens assembly housing

(112) , and the light emitter or light guide (110), NIR light source (104), and control circuitry (106) may be mounted on and/or enclosed in a portable computing device housing or case. The optical lens assembly housing (112) may be detachably coupled to the portable device case (114). For example, the portable device case may comprise an optical lens assembly mount (118) having a recess (1 16) that is configured to receive a portion of the optical lens assembly housing (1 12) such that light from the NIR light source (104) and/or light guide (1 10) may be directed through the optical lens assembly (102) toward a patient's eye. For example, the optical lens assembly may comprise a first beam splitter located in a portion of the optical lens assembly housing that is, when coupled to the portable device case, in optical connection with the light guide and the NIR light source. Illumination of the eye using light from the NIR light source and/or the light guide may be provided through the first beam splitter to the other components of the optical lens assembly. The control circuitry may determine whether the illumination light is provided by the NIR light source or by the light guide (i.e., the light guide alone or in combination with the NIR light source). In one variation, the control circuitry may comprise a light-dependent resistor that activates or deactivates the NIR light source depending on its resistance value. The light guide may be positioned adjacent to the light-dependent resistor such that the amount of light output by the light guide or light emitter changes a resistance value of the light-dependent resistor. For example, if the light guide output is high, the change in the resistance of the light-dependent resistor may cause deactivation of the NIR light source, so that illumination of the eye is provided by light from the light guide. If the light guide output is low (or no light at all), the change in the resistance of the light-dependent resistor may cause activation of the NIR light source, so that illumination of the eye is provided by light from the NIR light source. Alternatively or additionally, in some variations, the detachable imaging system may comprise a light source that emits light in other spectral ranges, for example, light having wavelengths from about 400-500 nm, or from about 200-400 nm. The optical lens assembly may comprise one or more optical components, such as various polarity filters (e.g., S- phase and P-phase filters), beam splitter(s), and/or relay lenses, and/or objective lenses that may help to alleviate unwanted glare.

[0028] When the detachable imaging system is assembled with a portable computing device such as a smartphone, a patient's pupil may be dilated by illuminating the eye with the NIR light source (i.e., without the use of mydriatic agents). Optionally, the patient may be exposed to a low-light or dark environment for an interval of time prior to imaging (e.g., from about 15 minutes to about 45 minutes, about 20 minutes, about 30 minutes, etc.) to facilitate pupil dilation. For example, the patient may wear a pair of glasses having color-tinted filtered lenses that may artificially dim ambient light and/or allow the transmission of NIR light for a period of time before the screening, which may also help to promote dark adaptation. The clinician or technician may examine the field-of-view provided by the imaging system through the dilated pupil as displayed in a preview frame of the smartphone camera application to confirm that the region of interest in the fundus is focused and within the field-of-view. The clinician may then trigger the smartphone camera to acquire an image by, for example, pressing a button, key, and/or graphic on a touch-sensitive screen of the smartphone. Alternatively or additionally, the clinician may also acquire images using in the auto-capture mode described above and capture images of the patient automatically when certain events and/or pattern of events are detected. This may trigger a brief and rapid visible (e.g., white) light pulse from the smartphone light source (i.e., flash). The visible light from the smartphone light source may be captured by the light guide (e.g., fiber optic cable) and transmitted to the control circuitry, where the light may change a resistance value of the light-dependent resistor. This change in resistance may deactivate the NIR light source. In addition, the light from the smartphone may be transmitted to the optical lens assembly to briefly and rapidly illuminate the eye while the fundus image is acquired by the smartphone image sensor. The image may be acquired before the pupil constricts in response to the visible light. For example, the smartphone light pulse may have a duration of 0.001 second to about 1 second (e.g., about 0.01 second, about 0.5 second), and the image sensor may capture an image of the eye about every 0.01 second to about 0.25 second during the light pulse. After the smartphone light pulse ends, the resistance value of the light-dependent resistor may change (e.g., revert to its previous value), which may activate the NIR light source. The eye may then be illuminated in NIR light, which may help maintain or re-establish pupil dilation for the acquisition of subsequent images. For example, after a smartphone light pulse ends, the eye may be illuminated by NIR light (or no light at all) for about 5 seconds to about 10 seconds to re-establish pupil dilation. The light-dependent resistor of the control circuitry provides optical triggering of the detachable imaging system with the smartphone, without requiring an electrical connection. The flash from the smartphone acts as an optical signal to the detachable imaging system that an image is about to be acquired and that the NIR illumination should be stopped so that the eye can be illuminated with visible light from the smartphone flash. [0029] In some variations, all of the components of the detachable imaging system may be enclosed in a single housing and/or integrated on a single mounting substrate, in other variations, the different components may be grouped and enclosed in separate housing modules, which may be assembled at the time of use by the clinician or technician. For example, components that may be relatively less expensive to manufacture and/or may change as portable computing devices are updated may be included in a housing separate from components that remain largely the same (or unchanged) across portable computing device updates and/or may be relatively more expensive to manufacture. For example, the optical lens assembly may remain the same across multiple portable computing devices while the case (e.g., attachment feature) may change across different portable computing device types and updates. In one variation, a detachable imaging system may comprise an optical lens assembly and a portable computing device case, where the optical lens assembly is detachable from the portable computing device case. The optical lens assembly itself may also comprise detachable optical modules, which may facilitate optical adjustments and customizations, as may be desired.

Optical Lens Assembly

[0030] One variation of a detachable imaging system for acquiring non-mydriatic images of an eye may comprise an optical lens assembly that is configured to direct illumination light to the eye and to capture and/or optically modify (e.g., by filtering or focusing) light returning from the eye for acquisition by the image sensor of a portable computing device. The optical lens assembly may also comprise one or more optical components and arrangements to help reduce glare from the eye. The optical lens assembly may also comprise one or more optical components (e.g., beam splitters) that may direct illumination light with different wavelengths to the eye. One variation of an optical assembly may comprise an objective lens, one or more optical components for providing illumination to the eye (i.e., illumination optical components) through the obj ective lens, one or more optical components that collect light through the objective lens for imaging (i.e., imaging optical components), and a beam splitter that separates illumination light to the eye and imaging light returning to from the eye.

[0031] FIGS. 2A-2D depict one variation of illumination optical components (204) and imaging optical components (206) of an optical lens assembly (200). Illumination optical components (204) may comprise a collector lens (208) and a polarizing filter (210). Optionally, illumination optical components (204) may comprise an optional condenser (212) and a light guide/emitter and/or light source (not shown). The collector lens (208) may collimate light from a light guide and/or light source (such as from a NIR light source, and/or a visible light or white light LED, and/or from a light guide such as a fiber optic cable carrying light from the light source/flash of a smartphone), and may, for example, comprise a lens having a diameter of about 15-30 mm and a focal length of about 12-20 mm. The polarizing filter (210) may transmit light having a particular phase while blocking light with a different (e.g., orthogonal or perpendicular or opposite phase), where the phase of light that is transmitted is aligned with (e.g., matches) the phase of light that is reflected by the beam splitter. For example, the polarizing filter (210) may transmit S-phase light (i.e., block P-phase light) to the polarizing beam splitter (214), which may reflect S-phase light. In some variations, the polarizing filter (210) may comprise a glass linear polarizer having a diameter of about 12-30 mm. The optional condenser (212) may be configured to focus the S-phase light from the polarizing filter (210) onto the polarizing beam splitter (214), and may comprise a lens having a diameter of about 9-20 mm and a focal length of about 20-50 mm. S-phase illumination light from the condenser (212) may be reflected by the polarizing beam splitter (214) and directed to an objective lens (216) toward a patient's eye. The polarizing beam splitter (214) may have any size, and may be configured to reflect light of one phase and transmit light of another phase (e.g., orthogonal or perpendicular or opposite phase). In this variation, the polarizing beam splitter (214) reflects S-phase light and transmits P-phase light, which turns the illumination light from the condenser by about 90° to direct it to the objective lens (216), and may comprise a square glass substrate polarizer having a length/width from about 12.5 mm to about 25 mm. The proportion of light that is reflected and the proportion of the light that is transmitted by the polarizing beam splitter (214) may also vary and may, for example, be about 90% reflected and about 10% transmitted, or may be about 50% reflected and about 50% transmitted, or may vary up to about 99% reflected to about 1 % transmitted. Light from the eye returning through the objective lens (216) may pass through the polarizing beam splitter (214) and the imaging optical components (206) before the light is acquired by the image sensor of the smartphone. One variation of imaging optical components (206) may comprise a second polarizing filter (218) and a relay lens (220). As indicated above, the polarizing beam splitter (214) transmits P-phase light (and reflects or blocks S-phase light), so the light that passes through the relay lens (220) is P-phase light. In other variations, the polarity of the filters and polarizing beam splitter may be reversed. Such a "cross-polarization" arrangement of optical components between the illumination light and imaging light may help to reduce glare and/or light scatter or noise that may arise from the illumination light. The second polarizing filter (218) may provide additional filtering to further reduce glare. For example, the second polarizing filter (218) may be transmit P-phase light and may comprise a glass linear polarizer having a diameter from about 12 mm to about 40 mm. The relay lens (220) may help to adjust the focal length so that the light from the eye is incident on the portable computing device (e.g., smartphone) image sensor, and may have a diameter that approximates the diameter of the smartphone camera lens. For example, the relay lens (220) may comprise a lens having a diameter from about 5 mm to about 20 mm (e.g., from about 10 mm to about 11 mm), and a focal length from about 20 mm to about 50 mm. The diameter of the relay lens (220) may be sized such that other optical components of the portable computing device (e.g., flash light source) are not obstructed by the lens. It should be understood that in other variations, the polarities of the filters and beam splitters described above may be reversed.

[0032] The optical lens assembly may comprise a housing comprising a plurality of grooves, slots, recesses, protrusions, notches, and the like for retaining the optical components described above. FIG. 2D depicts an exploded side view of one variation of an optical lens assembly (200) comprising an optical lens assembly housing (230), illumination optical components (204) and imaging optical components (206). The illumination optical components (204) may comprise an illumination light beam splitter (207), a collector lens (208), a polarizing filter (210), and a condenser (212). As depicted in FIGS. 2D and 4A, the housing (230) may comprise a first recess (232) sized and shaped to retain the illumination light beam splitter (207), a second recess (234) sized and shaped to retain the collector lens (208), a third recess (or slot) (236) sized and shaped to retain the polarizing filter (210), and a fourth recess (238) sized and shaped to retain the condenser (212). The housing (230) may have a diagonal slot (240) located above the fourth recess (238), the diagonal slot (240) configured to retain a polarizing beam splitter (214) that directs the light from the illumination optical components (204) to the objective lens (216) (and onward to a patient's eye). The housing (230) may also comprise one or more grooves, slots, recesses, protrusions, notches, and the like for retaining the imaging optical components (206), such as the second polarizing filter (218) and the relay lens (220). The housing (230) may comprise a groove (242) that is sized and shaped to retain both the second polarizing filter (218) and the relay lens (220). The groove (242) may have an opening (244) where the imaging light passes through the relay lens (220) to the imaging sensor of the smartphone. The opening (244) may comprise a beveled edge (246) around the circumference of the opening (244) (FIG. 2D). Alternatively or additionally, the opening (244) may be located in a notch (245), where the notch comprises a beveled edge (246), as depicted in FIG. 4B. The beveled edge may have an angle and/or edge thickness that may be configured to engage smartphones that have a camera lens that protrudes from the smartphone housing. The beveled edge may also help provide additional shielding from light emanating from an adjacent smartphone flash light source and/or ambient light/glare entering around the smartphone camera lens, which may help improve image quality. In addition, as will be described in greater detail below, the beveled edge may also track and/or contour around a protruding lens of a smartphone camera to provide an anchor point for the optical lens assembly housing to lock over the smartphone housing (when used in conjunction with the portable computing device case of the imaging system).

[0033] The objective lens (216) may comprise an ophthalmic examination lens between about 30 diopters and about 80 diopters, for example, a 54 diopter ophthalmic examination lens with a 18.5 mm focal length, and may be located about 38.5 mm away from the relay lens (220) having a focal length of about 20 mm to about 25 mm. In some variations, a 60 diopter or 78 diopter ophthalmic lens may be placed at a distance equal to the focal of length of the objective lens and the focal length of the relay lens. In some variations, the distance between the objective lens (216) and relay lens (220) may be adjusted, which may help to tailor the optical lens assembly to address any refractive errors and/or variability in a patient's eye (e.g., due to anatomical variations in cornea thickness, distance between the anterior chamber and the fundus, corrective lenses such as glasses or contact lenses, etc.) so that a focused image may be acquired by the smartphone image sensor. In some variations, the objective lens may be detachable and/or movable relative to the relay lens. For example, the relay lens (along with one or more of the other components of the optical lens assembly) may be enclosed in a housing comprising an attachment region (250) with a plurality of threaded protrusions (252) and the objective lens mount (215) may comprise a receiving region (254) with a plurality of threaded grooves (256) that correspond with the threaded protrusions (252). Engaging the threaded grooves (256) of the objective lens mount (215) with the threaded protrusions (252) of the optical lens housing (230) may align the center of the objective lens (216) with the center of the relay lens (220), defining a longitudinal axis (260) between the objective lens center and the relay lens center. Turning the objective lens mount may cause the objective lens to travel along the longitudinal axis, changing the distance between the objective lens and the relay lens. A clinician or technician may turn the objective lens mount while inspecting a patient's eye to focus the image/view on the desired region of the eye, compensating for any refractive variations in the patient's eye. Alternatively or additionally, the relay lens may be movable along the longitudinal axis to adjust the image focus. For example, the relay lens may be attached to a slidable mount with a slider mechanism (e.g., manually adjustable or slidable, and/or adjustable or slidable using an actuator or motor). In some variations, the objective lens mount (along with the objective lens attached on the mount) may be de-coupled from the optical lens assembly housing, and exchanged with a different objective lens and mount. A different objective lens and mount may be used for patients with greater refractive variability or fluctuations, and/or for imaging different regions of the eye, and/or for replacing a faulty objective lens and mount. Alternatively, in some variations, the distance between the objective lens and the relay lens may be fixed.

[0034] An objective lens mount may retain or secure an objective lens using any suitable retention mechanism. FIGS. 3A and 3B depicts one variation of an objective lens mount (300) to which the objective lens (216) may be coupled. The objective lens mount (300) may comprise a groove or slot (302) that has a circular track with a radius and/or diameter that approximates the radius and/or diameter of the objective lens (216). An objective lens mount (300) may comprise a lens release mechanism that allows the objective lens to be removed for repair and/or replacement with a different objective lens with different optical properties (e.g., objective lenses for imaging the anterior portion of the eye instead of the posterior portion of the eye, patients with different eyeglasses prescriptions, etc.). For example, the objective lens mount (300) may comprise two or more shells or frames (304) that may be configured to clamp the objective lens therebetween and secured (e.g., with a latch, elastic band, screw, and/or any other detachable attachment mechanism). In FIGS. 3A and 3B, the objective lens mount (300) comprises first and second frames (304a, 304b) that are symmetric, each contacting half the circumference of the objective lens (216), and having an attachment mechanism (308) for attaching the first and second frames together to retain the objective lens (216) between them. The attachment mechanism (308) may comprise, for example, first and second threaded bores (310a, 310b) on the first and second frames, respectively, and a screw having a corresponding threads and a length that extends through both the first and second threaded bores (also depicted in FIGS. 2A-2B). Aligning the first and second bores and threading the screw therethrough may secure an objective lens that is clamped between the first and second frames. Alternatively, the objective lens mount may be configured to retain an objective lens permanently, such that the objective lens is not removable from the mount. To use a different objective lens, the entire lens and mount may be removed and replaced with a different objective lens (e.g., having the same or different optical properties) and mount. Alternatively the objective lens may be enclosed in the same housing as the other components of the optical lens assembly (including the relay lens).

[0035] As described above, glare from the illumination light and/or other scattered light in the eye may be mitigated or reduced using a cross-polarizing optical arrangement, where one or more polarizers located within the illumination light path direct single polarity or phase (e.g., either S-phase or P-phase) light to the eye, while one or more polarizers located within the retum light path (i.e., imaging light path) select for light having a polarity or phase opposite to that of the illumination light (e.g., P-phase or S-phase). One or more additional glare-mitigation techniques and arrangements may be used. One variation of an optical arrangement for glare- mitigation may comprise illumination optical components that direct illumination light having a first central axis (i.e., a line between the center of one or more of the illumination optical components (204) and the focal point of illumination) and imaging optical components (206) that collect light along a second central axis (i.e., a line between the center of one or more of the imaging optical components (206) and the imaging focal point), where the first central axis may be offset from the second central axis. FIG. 5 provides a schematic depiction of an iris (504) and the placement of the illumination focal point (500) (e.g., along the first central axis (261)) and the imaging focal point (502) (e.g., along the second central axis (260)) within a dilated pupil (506). Offsetting the illumination focal point (500) from the imaging focal point (502) may help to reduce unwanted reflected light or glare from the illumination light, which may help to improve image quality. FIG. 2D depicts one variation of an optical lens assembly where the first and second central axes of the illumination optical components (204) and the imaging optical components (206) are offset. The first line (261) represents the central axis of the illumination light (i.e., first central axis that extends between the illumination focal point (500) and the center of the beam splitter (214)) and the second line (260) represents the central axis of the imaging light (i.e., second central axis that extends between the imaging focal point (502) and the center of the relay lens (220), and may optionally extend through the center of the objective lens (216)). The first central axis (261) and the second central axis (260) may be offset from each other by a distance Doffset of about 1.25 mm. For imaging a fundus region of an eye through a pupil that has been dilated without a mydriatic agent, the total diameter D_pupii of the pupil may be about 3 mm. If the axis of the imaging light (i.e., the second central axis (260)) is centered through the pupil, the axis of the illumination light (i.e., the first central axis (261)) may have be offset from the axis of the imaging light by a distance Doffset of about 1.5 mm or less. A greater offset may result in the illumination light not passing through the dilated pupil (i.e., having a diameter of about 3 mm) and providing little (if any) illumination to the fundus. The size of the focal spot of the illumination light on the fundus region through the cornea/pupil may be from about 0.25 mm to about 2.5 mm (e.g., about 0.5 mm, about 1 mm). In the example depicted in FIGS. 2D and FIG. 5, the center of the beam splitter (214) may be shifted up or down in a direction that is perpendicular to the first and/or second central axes so that the illumination light from the condenser (212) strikes the beam splitter (214) center at an offset distance from the second central axis (260). Alternatively or additionally, offsetting the first central axis relative to the second central axis may be attained by laterally shifting (i.e., in a direction parallel to the first and/or second central axes) the condenser (212), polarizing filter (210), and collector lens (208) so that the illumination light from these optical components do not strike the center (215) of the beam splitter (214) (i.e., the center points of these optical components are not collinear with the center point of the beam splitter), and/or are instead being reflected at a point that is off-center. In some variations, the center points of the condenser (212), polarizing filter (210), and collector lens (208) may be aligned with the center point (215) of the beam splitter (214), and the offset between the first axis (261) and the second axis (260) may be introduced by including a prism between the condenser (212) and the beam splitter (214), where the prism may shift the illumination light from the condenser to the beam splitter. [0036] As described previously, non-mydriatic pupil dilation may be induced by NIR illumination of the eye, and when an image of the fundus region is desired, a brief pulse or flash of white light is provided at the moment of image acquisition (i.e., so that the image may be acquired before the pupil constricts). The illumination optical components (204) of an optical lens assembly may comprise an illumination light beam splitter that directs light from two different illumination light sources or emitters to provide two or more types of illumination to the eye. In the variations described herein, the white light may be provided by a light source (e.g., the flash light source) of a smartphone, however, it should be understood that the white light used for image acquisition may be any light source, for example, one or more LEDs of the optical lens assembly and/or portable computing device case. FIG. 2D depicts one variation of an optical lens assembly comprising a beam splitter (207) having an asymmetric reflection-to- transmission ratio. In variations where the white light source is the flash light source from a smartphone and the NIR light source is an LED of the detachable imaging system, the illumination light beam splitter (207) may be selected and arranged such that the higher transmission or reflectance surface of the beam splitter is in the light path of the white light source or emitter and the lower reflectance or transmission surface is in the light path of the NIR light source. For example, the transmittance of white light from the smartphone flash across the illumination light beam splitter (207) may be about 75% while the reflection of NIR light from an LED is about 25%. This arrangement may help to increase the proportion of the illumination from the smartphone flash light source that is directed to the eye, since the light output or intensity from the flash light source is a fixed quantity set by the smartphone manufacturer. There may also be some intensity loss along the fiber optic cable that optically connects the flash light source and the illumination light beam splitter. In contrast, the NIR light source is a component of the detachable imaging system, and if a greater NIR output or intensity is desired, the NIR light source may be positioned closer to the illumination light beam splitter, and/or the magnitude of the electrical current or power supplied to the NIR light source may be increased, and/or a higher output or higher intensity NIR light source may be selected for inclusion with the detachable imaging system. In some variations, the illumination light beam splitter may be a non-polarizing beam splitter, which may help to increase the illumination light intensity to the eye. In particular, for an optical lens assembly comprising multiple stages of polarizing filters and optical elements (such as the cross-polarizing optical arrangements for glare reduction described above) that may already attenuate the illumination and imaging light (e.g., each polarization stage may reduce intensity by about 50%), white light intensity loss across the optical fiber (e.g., of about 50%), a non-polarizing illumination light beam splitter may help limit further light attenuation by maintaining the light intensity provided by the illumination light sources.

[0037] While illumination light from multiple light sources may be directed through a beam splitter as described above, in other variations, illumination light from multiple sources may be directed through one or more shutters, color wheels, mirrors or reflectors, beam splitters, and/or prisms.

Portable Computing Device Case

[0038] A detachable imaging system for acquiring non-mydriatic images of an eye may comprise a portable computing device case. In some variations, the portable computing device case may be integrally formed with the housing of the optical lens assembly, while in other variations, the device case may be detachable from the optical lens assembly. This may allow the device case to be adapted for various portable computing device form factors and/or changes in the housing of portable computing devices, while keeping re-using the optical lens assembly across multiple devices and/or device housing shapes/sizes. A portable computing device case, such as a smartphone case, may comprise a frame having one or more attachment mechanisms for coupling the case to the device and a light conduit configured to optically connect the light source of the smartphone camera to the optical lens assembly. In one variation, the light guide (or light emitter) may be a fiber optic cable (i.e., optical cable) and the device case may further comprise an optical cable holder or mount with that secures one end of the optical cable (i.e., a first end of the cable) at a location corresponding to the location of the smartphone light source. The cable holder or mount may comprise an enclosure made of an opaque or light-blocking material with an opening that may be, for example, friction-fit over the optical cable. The cable holder or mount may optionally include a flange, lip or other structure that may help further shield the smartphone camera from the smartphone light source. In some variations, a second end of the optical cable may be positioned adjacent to the illumination light beam splitter, so that when the smartphone flash is activated, the light from the flash is directed to the illumination light beam splitter onto the patient's eye via the illumination optical components described above. The length of the optical cable between the first end and second end of the cable may be curved, having one or more curves such that light loss along the cable length is reduced and/or the optical cable remains bounded by an area (e.g., back surface area) of the smartphone. As described previously, some variations of a smartphone case for a detachable imaging system may also comprise a NIR light source that may be activated based on the activation of the smartphone flash light source. That is, the smartphone flash light source may function as an optical trigger from the smartphone to the detachable imaging device that the clinician or technician wishes to acquire an image, without requiring electronic communication (e.g., wired or wireless electrical communication) from the smartphone to the detachable imaging device indicating that the clinician or technician wishes to acquire an image. In one variation, a smartphone case may comprise control circuitry in electrical communication with an NIR light source (e.g., NIR LED), where the control circuitry comprises a light-dependent resistor having resistance values that change according to illumination from the smartphone flash light source. Alternatively or additionally, a smartphone case may comprise a white light source that is optically connected to the first end of the cable. The smartphone case may further comprise a communication module that provides electrical communication (wired or wireless, e.g., Bluetooth) between the smartphone and the white light source . When an image is to be acquired, a command is sent from the smartphone to the communication module, which activates the white light source causing a transmission of light through the optical cable that deactivates the NIR light source and transmits illumination light to the eye. In some variations, the white light source of the smartphone case may have a higher light output than the light source of the smartphone.

[0039] One variation of a smartphone case of a detachable imaging system for acquiring non- mydriatic images of an eye is depicted in FIG. 6A (the objective lens assembly is omitted for the sake of clarity). A smartphone case (600) comprises a frame (602) comprising two or more clips or feet (604) along its perimeter for engaging the perimeter of a smartphone (601). The smartphone (601) may comprise a camera lens (603) and a flash light source (605) adjacent to the camera lens. For example, the clips or feet (604) may comprise a protrusion and/or lip that wrap around the edge of the smartphone, having a length that approximates the thickness of the smartphone. In this variation, the smartphone (601) may be slid in the direction of arrow (606) (e.g., vertical direction), as depicted in FIG. 6C into engagement with the smartphone case (600). The clips or feet (604) may allow relative motion between the smartphone and the smartphone case in the vertical direction, but may limit lateral motion (i.e., in a direction perpendicular to the vertical direction represented by arrow (608)). The smartphone case (600) may also comprise a fiber optic cable (608) with a first end (610) coupled to a cable holder or mount (612) and a second end (614) coupled to an objective lens assembly mount (616). As depicted in FIGS. 6A-6D, the objective lens assembly mount (616) may comprise a slot (618) that corresponds with the size and shape of the portion of the objective lens assembly housing with the illumination light beam splitter. The objective lens assembly mount (616) may also comprise an opening (620) having a diameter that corresponds with the diameter of the optical cable, and an opening or window for NIR illumination from an NIR light source. The NIR light source may be located within the objective lens assembly mount housing, and/or may be located outside of the objective lens assembly mount (616), but provide NIR illumination through an opening or window in the housing of the optical lens assembly (e.g., window (231) depicted in FIG. 2A such that NIR illumination is directed to the illumination light beam splitter and to the patient's eye, as explained previously. In the variation depicted in FIGS. 6A-6B, the NIR light source (e.g., NIR LED (624)) is located within a light source enclosure (622) of the smartphone case, which may comprise opaque (e.g., light-blocking) walls that limit or block stray NIR light from illuminating the optical cable. The NIR light source may be encased within the enclosure (622), with only the electrical leads or connections (626) extending from the enclosure (622). The light source enclosure may comprise an opening or window that abuts or is otherwise optically connected to the opening or window of the objective lens assembly mount (616), so that NIR light may impinge on the illumination light beam splitter. The smartphone case may also comprise a shell made of an opaque material that fits over the frame, enclosing the components depicted in FIGS. 6A-6D. This may help to limit or block any light that may leak from the fiber optic cable (608) and associated mounts to shield the clinician and patient from unwanted illumination. One variation of a shell (650) that may be configured to fit over the frame and to enclose the components depicted in FIGS. 6A-6D is depicted in FIG. 6E. Shell (650) may fit over the frame (602) and may be attached to the frame (602) via one or more screws (not shown) and threaded bores (652). In some variations, the shell may be large enough to enclose the portable computing device (e.g., smartphone). Alternatively or additionally, some variations may comprise a second shell that encloses a smartphone and retains it within the device case such that the smartphone is enclosed with only the screen viewable and accessible from outside the second shell. While the variations described herein comprise a portable computing device case that allows for slidable attachment and removal of a computing device (e.g., without additional or specialized tools or adhesives, without excessive force, etc.), it should be understood that in other variations, the portable computing device may be fixedly coupled to the case. In such variations, the portable computing device may be secured to the case using one or more adhesives, screws and threaded bores, and/or may be secured to the case by welding, soldering, and the like.

Optical Cable

[0040] Some variations of a detachable imaging system for acquiring non-mydriatic images of an eye may comprise a light guide such as one or more fiber optic cables. A fiber optic cable (referred to as an optical cable) may comprise a fiber optic cable where some light emanates from the side walls of the cable, known as evanescent waves. The diameter of an optical cable may be selected to approximate or match the diameter of the smartphone flash light source and/or aperture of the smartphone housing from which the flash light is emitted. For example, the diameter of an optical cable may approximately be greater than or equal to the diameter of the smartphone housing flash light source aperture, and may have a diameter from about 4 mm to about 6 mm (e.g., an inner cable diameter of about 5 mm for a smartphone housing aperture of about 4.5 mm, an inner cable diameter of about 4.5 mm for a smartphone housing aperture of about 4 mm, etc.). This may help to improve the capture efficiency of the light produced by the smartphone for guidance to the optical lens assembly. In some variations, the sidewalls of the optical cable may be coated with an optically opaque and/or reflective coating (e.g., aluminum, silver, etc.), and/or may be enclosed in a sheath to help reduce light leakage along its length. The outer surface or layer of the optical cable may comprise a material that promotes reflection or internal scattering of light within the diameter and length of the cable, with may help reduce light loss along the cable length. Alternatively or additionally, some variations may comprise a group or bundle of fiber optic cables that each have a smaller diameter than the light source (e.g., fiber optic with 0.125mm) that, when bundled together, cover the light source. Some variations may comprise one or more optical fibers with or without cladding, multimode fiber, a light pipe, and/or a rigid light-transmitting rod.

[0041] As described above, the first end of the optical cable may be secured at a location on the smartphone case that corresponds with the location of the smartphone flash and the second end of the optical cable may be secured at the objective lens assembly mount (616). The longitudinal portion of the cable between the first and second ends (610, 614) may be curved such that the cable remains within the boundaries of the case. The one or more curves of the optical cable (608) may have a bending radius that facilitates continuous and/or uninterrupted light transfer across the length of the cable. In some variations, an optical cable may have a threshold radius of curvature (or a threshold bending radius) where a cable curve or bend that does not exceed the threshold allows the cable to continue to channel light without light loss beyond an acceptable tolerance or efficiency. If the optical cable has a bend that exceeds (i.e., is tighter than, having a radius of curvature that is smaller than) the threshold bending radius or radius of curvature, light loss may exceed the acceptable tolerance and/or may disrupt or truncate the light transmission between the first and second ends of the cable. In some variations, the bending radius may be less than or equal to about ten times the diameter of the cable (e.g., a cable having a diameter of about 5 mm may have a maximum bending radius or radius of curvature of about 50 mm). As depicted in FIGS. 6A-6D, the position and orientation of the first end of the optical cable may be secured by a cable holder or mount (612). The cable mount (612) may comprise a cable lumen (613) having a location that corresponds with the location of the smartphone flash light source and an orientation that is approximately perpendicular to the smartphone housing for a length before the lumen curves toward being approximately parallel to the smartphone housing. The curve (615) of the cable mount lumen (613) may position and secure the optical cable (608) such that the face of the first end of the optical cable is aligned with the smartphone flash light source when the smartphone is retained within the case. Aligning the face of a fiber optic cable end along the direction of light from a light source may help to increase the amount of light captured within the cable from the light source. If the end of the fiber optic cable is not generally aligned with the direction of light from the light source, or is at an angle that exceeds a threshold angle from the light direction, light from the light source may not enter the cable. That is, if the end of the fiber optic cable is not aligned with the light source and/or the direction of the light emanating from the light source within a threshold alignment angle, insufficient light may be captured in the cable, and little if any illumination may be provided to the optical lens assembly (e.g., the more parallel the optical cable is to the light source, the higher the percentage of light output from the source will be captured and transmitted via the cable). The curved lumen of the cable mount may help to align the optical cable with the smartphone light source at the first end, and then guide it in a curve that may be approximately parallel to the plane of the smartphone housing. In this variation, the path of the optical fiber may have a first curve (630) and a second curve (632), where the ROC of the first and second curves do not exceed the threshold bending radius beyond which light conduction is lossy and/or interrupted (e.g., less than or equal to about ten times the diameter of the cable, as described above). The second end of the optical cable may pass through a slot or opening of the optical lens assembly mount, for optically coupling to the illumination light beam splitter.

[0042] A cable holder or mount (612) may comprise one or more structures to help enclose or shield the light from the smartphone light source, and in particular, shield the light from the smartphone light source from the patient (exposure to white light may interfere with pupil dilation) and/or the smartphone image sensor and/or camera optics. For example, a cable mount may comprise a flap that extends from the walls of the cable mount enclosure (e.g., a light shielding flange (634) of FIGS. 6A, 6B, 6D) that may extend along the surface of a smartphone housing to fill in any gaps or spaces between the housing of the optical lens assembly and the smartphone housing so that light from the smartphone light source does not scatter or leak over to the smartphone image sensor. The additional shielding of the smartphone camera may help to reduce glare and ambient lighting that may be caused by stray light from the smartphone light source. The light shielding flange (634) may be located between the smartphone camera and light source and may act as an additional light barrier between these two components. In some variations where the optical lens assembly housing comprises a groove with an opening having a beveled edge around the circumference of the opening (e.g., as described above and depicted in FIG. 4B), the flange (634) may be shaped to fit engaged with the beveled edge within the groove, which may help shield the smartphone camera lens and/or image sensor from unwanted ambient light that may degrade the image quality. [0043] Control circuitry for the activation and deactivation of the NIR light source may be located along a portion of the optical fiber. A light pulse or flash from smartphone light source may function as a trigger that controls the operation of the NIR light source. As described previously, the control circuitry may comprise a light-activated electrical components such as a light-dependent resistor or a photodiode and may be in electrical communication with the NIR source (e.g., NIR LED). A light-dependent resistor is a resistor whose resistance value varies based on the light that is incident on the resistor. In some variations, increasing the illumination on a light-dependent resistor may reduce its resistance value while in other variations, decreasing the illumination on a light-dependent resistor may reduce its resistance. The light- dependent resistor and the optical cable may be positioned adjacent to each other so that light passing through the optical cable may illuminate the light-dependent resistor. In some variations, the light-dependent resistor may be enclosed in an opaque housing (e.g., a light-tight enclosure) that has two ports or openings for the passage of the optical fiber through the housing. The housing may help to shield the light-dependent resistor from any light source and/or stray light so that changes in its resistance value are based primarily on the light within the optical cable (e.g., side-glow illumination from the side walls of the optical cable). FIGS. 6A-6D depict one example of an opaque housing (636) that encloses a light-dependent resistor (638) of a control circuit. As shown in FIG. 6C, the light-dependent resistor housing may have a side opening (640) that allows for the insertion of the light-dependent resistor (638) into the housing, after which a removable cover is applied to close the housing. The light-dependent resistor housing (636) may comprise two slits or slots for the resistor terminals or leads. The light-sensitive portion (637) of the resistor may be enclosed within the housing (636), while the resistor leads or terminals (339) may extend outside of the housing and be electrically connected to the control circuitry, which may be located outside of the housing (636). The NIR LED (624) may be located within a light source housing or enclosure (622), where the light-emitting portion of the LED is located entirely within the enclosure (622), and the leads or terminals (626) of the LED may extend outside of the enclosure. The leads or terminals of the NIR LED and the light- dependent resistor may be electrically connected to the control circuitry, which may be located between the light source housing and the light-dependent resistor housing. Control Circuitry

[0044] One variation of a control circuitry for the NIR light source (e.g., LED) is

schematically depicted in FIG. 7. The control circuitry (700) may comprise a mounting substrate (e.g., a printed circuit board or PCB), a power source (702), a light-dependent resistor (704), a resistor (706), and a transistor (708) (e.g., a bipolar junction transistor or BJT). The positive terminals of the resistor (706) and the NIR LED (701) may be connected to the positive terminal of the power source (702) (e.g., a battery), while the negative terminal of the light-dependent resistor (704) and the emitter of the transistor (708) may be connected to the negative terminal of the power source (702). The negative terminal of the NIR LED (701) may be connected to the collector of the transistor (708) and the base of the transistor (708) may be connected to the negative terminal of the resistor (706) and the positive terminal of the light-dependent resistor (704). That is, the resistor (706) and the light-dependent resistor (704) may be connected in series. The light-dependent resistor (704) may be positioned adj acent to the optical cable such that illumination from the optical cable side walls can activate the light-dependent resistor (704). When the smartphone light source is off, no photons from the optical cable strike the light- sensitive portion of the light-dependent resistor. In this state, the light-dependent resistor may have a high resistance value, which may induce current flow between the collector and emitter of the transistor, which in turn activates the NIR LED. The NIR illumination of the patient's eye helps to encourage non-mydriatic dilation of the pupil. When the smartphone light source is on (e.g., when the clinician decides to take an image and activates the smartphone camera and light source), photons from the smartphone light source are captured by the optical cable and transmitted along the cable, where side glow from the cable may illuminate the light-sensitive portion of the light-dependent resistor. In this state, the light-dependent resistor may have a low resistance value, which may reduce or turn off current flow between the collector and emitter of the transistor. Without electrical current flow across the NIR LED, the NIR LED is shut off. The (white) light from the smartphone light source passes through the optical lens assembly and illuminates the eye with a light pulse/flash as an image of the eye is acquired by the smartphone camera image sensor.

[0045] The sensitivity of the control circuitry to illumination from the optical fiber may be modulated by adjusting the value of the resistor (706) and/or the light-dependent resistor (704). In some variations, the light-dependent resistor may be a CdS photocell LDR (such as a light- dependent resistor by ADVANCED PHOTONIX, INC.). The light-dependent resistor transition time between low high resistance values and low resistances values may be about 10 ms or less, otherwise, a smartphone camera that acquires images at about 1/100 second shutter speed may acquire an image with residual NIR illumination (due to incomplete NIR LED deactivation). This may introduce a color skew into the acquired image, caused by the NIR light source. In one variation, a light-dependent resistor may have a sufficiently high resistance in the dark (with little or no illumination) such that current from the power source is diverted through the NIR LED. For example, a control circuit where the resistor (706) has a resistance value of about 32 kOhm, a light-dependent resistor may have a resistance value of about 200 kOhm in the dark and a resistance value of about 5-10 kOhm under illumination, and may transition between these two resistance values in about 10 ms or less to help ensure that the NIR LED is not activated during image acquisition. The activation sensitivity (i.e., the threshold light intensity or number photons that triggers a resistance value change) and/or wavelength sensitivity may be tuned to the light output and spectrum of the smartphone light source. For example, a light-dependent resistor may have an activation sensitivity of about 10 lux and a spectral range from about 400 nm to about 700 nm, which may be sufficiently responsive to the light output of a typical smartphone. While this variation of a control circuit comprises a light-dependent resistor, other variations of a control circuit may comprise a photodiode that may be arranged with other circuit components to activate and deactivate the NIR LED according to illumination sensed by the photodiode (e.g., illumination from the optical cable). Voltage or current changes in the control circuit due to changes in the photodiode parameters due to optical cable illumination may activate the NIR LED in the absence of cable illumination and deactivate the NIR LED in the presence of cable illumination.

[0046] The power source for the NIR light source may comprise an external battery source of any voltage, for example, a 6-volt battery. Alternatively or additionally, power for the NIR light source may be provided by the smartphone via a circuit board control and application or software interface with the smartphone. In some variations, the power source may comprise a rechargeable battery. [0047] While the non-optical components of the control circuitry (e.g. the resistor, transistor, power source) in the variation described above are not enclosed in their own housing, in other variations, the non-optical components of the control circuitry may be enclosed their own housing, or enclosed in the same housing as the light-dependent resistor, or enclosed in the same housing as the NIR LED. In variations where the control circuitry, light-dependent resistor and NIR LED are enclosed in the same housing, additional light shielding structures or enclosures may be provided over the light-dependent resistor and/or NIR LED to help ensure that stray light from the NIR LED does not impinge on the light-sensitive portion of the light-dependent resistor.

Optical Lens Assembly Housing and Portable Computing Device Case Interface

[0048] In some variations, the optical lens assembly and the portable computing device case of a detachable imaging device may be mounted on a single substrate and not detachable from each other, but releasably attached to a portable computing device. Alternatively, as described above, the optical lens assembly and portable computing device case of a detachable imaging device may be separate modules (i.e., in separate housings or enclosures) and may comprise one or more attachment mechanisms for engaging and securing to each other and/or a portable computing device. One variation of the attachment mechanisms for a smartphone is

schematically depicted in FIGS. 8A and 8B. A smartphone (800) may comprise a camera (802) with an image sensor and a (flash) light source. In many smartphones, the camera may have a lens surface that protrudes from the smartphone housing. Turning to FIG. 8A, relative motion between the optical lens assembly (804) and the smartphone case (806) and the smartphone may be reduced or eliminated by attachment mechanisms that secure these items together and limit motion in one or more directions. For example, horizontal motion between the case and the smartphone (represented in FIG. 8A by the horizontal arrow (808)) may be limited or eliminated by clips or feet on the side of the case that restrain lateral motion while permitting vertical motion (for the smartphone to slide into the case). Vertical motion of the smartphone

(represented by vertical arrow (810)) relative to the case and optical lens assembly may be limited or eliminated by engagement of the optical lens assembly housing groove (e.g., as depicted in FIG. 4B) with the protruding lens surface, which may prevent the smartphone from sliding out of the case. The optical lens assembly housing (805) may be coupled to the case (806) by sliding the optical lens assembly (804)into the optical lens assembly mount (814), which may limit or eliminate relative vertical motion between the optical lens assembly (804) and the case (806) (vertical arrow (810) in FIG. 8 A). The beveled edge of the groove or notch of the optical lens assembly housing (805) may engage or encase the raised or protruding smartphone camera lens surface such that the smartphone cannot slide vertically past the notch out of the case unless the optical lens assembly is removed.

[0049] Turning to FIG. 8B, the optical lens assembly housing (804) may also comprise a groove (820) with a curved contour (822), which may correspond with the curvature (824) of the optical cable mount (826). Aligning these two contours may help to lock optical lens assembly housing with the case and/or may help to provide additional engagement of the detachable imaging system with the smartphone to prevent movement of the optical lens assembly and to maintain proper imaging alignment with the smartphone camera. That is, sliding the optical lens assembly (804) into engagement with the case (806) locks the detachable imaging system over the smartphone (800), so that the smartphone does not disengage horizontally or vertically from any component of the detachable imaging system. This may allow single-hand operation of the smartphone for image acquisition. By allowing a hand to remain free may facilitate more precise control of the position and/or stabilization of the smartphone and imaging system on the patient's face to acquire a more high-quality image and may also allow the clinician or technician to interact with the controls (e.g., touch screen) of the smartphone.

[0050] While a certain arrangement and relative positioning of various components of the detachable imaging system are depicted and described above, it should be understood that the position of one or more of these components may be modified in order to accommodate design changes and/or variations between different portable computing devices. For example, the optical lens assembly mount may be adjusted so that the optical lens assembly (e.g., the relay lens) is aligned with the portable computing device image sensor. The NIR light source may similarly be re-positioned depending on the position of the optical lens assembly mount. The location, size and shape of the optical cable mount may be adjusted based on the location of the portable computing device light source location, size and shape. [0051] Also described herein are kits comprising any of the imaging systems described herein. In some variations, a kit may comprise a first detachable imaging system comprising a near- infrared light source, and/or a second detachable imaging system comprising a white light source, and/or a third detachable imaging system comprising an ultraviolet light source, and/or a fourth detachable imaging system comprising a green or blue light source. Optionally, a kit may also comprise one or more dyes (e.g., fluorescent dyes such as fluorescein or indocyanine green) for application to the eye that may help facilitate the visualization of certain features of the eye. In one variation, a kit may comprise a first detachable imaging system with a white light source for white light imaging, a second detachable imaging system with a 400-500 nm light source for auto-fluorescence imaging, and a third detachable imaging system with a 200-400 nm light source for imaging of fluorescent dyes. For example, a kit may optionally comprise a fluorescence imaging device comprising an optical lens assembly, an ultraviolet light source that is optically connected to the optical lens assembly, and a control circuit that is electrically connected to the ultraviolet light source and optically connected to the portable computing device image sensor. A kit may optionally comprise an auto-fluorescence imaging device comprising an optical lens assembly, a blue or green light source that is optically connected to the optical lens assembly, and a control circuit that is electrically connected to the blue or green light source and optically connected to the portable computing device image sensor. Kits may optionally comprise one or more pairs of glasses to help simulate at dark or low-light environment.

Methods

[0052] A method for using a detachable imaging system for acquiring non-mydriatic images of an eye may comprise exposing the patient to dim, dark and/or red-tinted (e.g., NIR-tinted) lighting conditions to promote non-mydriatic pupil dilation, activating the visible light source of a portable computing device (e.g., flash light source that emits broad-spectrum light such as white light) to illuminate the patient's eye, and acquiring an image of the patient's eye using the image sensor of the portable computing device before the pupil constricts in response to the visible light. Exposing a patient to dim, dark, and/or red-tinted lighting conditions may comprise illuminating their eye with a red or NIR light source of a detachable imaging system coupled to a portable computing device (e.g., smartphone), and/or having the patient in a dim or dark room or a dim red-tinted room (e.g., for about 10 minutes to about 45 minutes), and/or having the patient wear a pair of glasses with red-tinted lenses that limit or block exposure to other wavelengths. These methods may be used alone or in combination to encourage non-mydriatic dilation and/or dark adaptation. One variation of a pair of glasses (900) that may help promote pupil dilation may comprise color-tinted filtered lenses (902) and a glasses frame (900) with large side and/or top and/or bottom bumpers (904) that may help to prevent side entry of light (FIG. 9A). Such glasses may be provided by, for example, NOIR MEDICAL TECHNOLOGIES (South Lyon, Michigan). The color-tinted filtered lenses may limit or block transmission of light having a wavelength less than about 580 nm, and allow transmission of light having a wavelength greater than or equal to about 600 nm (e.g., filter #93 of NOIR MEDICAL TECHNOLOGIES product suite). Such color-tinted filtered lenses, in conjunction with the large flaps or bumpers located on the sides of the frames, may artificially dim surrounding light and simulate a darkened room, which may promote non-mydriatic pupil dilation. A patient may be provided with these glasses at the start of a primary care visit to simulate a dark or dim environment, while still allowing them operate in normal lighting conditions. This would provide an extended period of time for the pupils to dilate as the patient proceeds with the other aspects of their primary care examination. Toward the end of the visit, which may be about 30 minutes to about 45 minutes after the patient first arrives and starts wearing the tinted glasses, the patient may then proceed to a dim or dark room where images of their eye (e.g., the fundus) may be acquired. This time period may coincide with the typical time duration for dark adaptation and may promote increased pupil dilation. The darkened environment may help maintain pupil dilation as the detachable imaging system and the smartphone acquire images of the fundus. As described above, image acquisition may comprise illumination of the eye with one or more brief pulses of white light and capturing the image of the fundus (or desired region of the eye) before the pupil constricts. To acquire successive fundus images while maintaining pupil dilation, the white light pulses may have a duration of about 0.5 seconds or less and waiting from about 5 seconds to about 30 seconds (e.g., about 5 seconds, about 5 second to about 8 seconds, about 8 seconds, about 10 seconds, etc.) between each image acquisition. During the waiting interval between image acquisition, the eye may be illuminated with NIR light, which may help maintain dilation and/or re-dilate the pupil to the extent it has constricted. [0053] Optionally, non-mydriatic dilation may be supplemented with the use of

pharmacological agents. For example, if it has been determined that the pupil is insufficiently dilated using non-mydriatic methods for the acquisition of a fundus image, the patient may be provided with one or more pharmacological agents to augment dilation. The quantity of the pharmacological agent may be less for a pupil that has been at least partially dilated using non- mydriatic methods (i.e., where the patient has been in a dim or dark environment and/or with NIR illumination) than for a non-dilated pupil (i.e., where the patient has been in a normal lighting environment with broad spectrum illumination). Examples of pharmacological agents may include an anti-cholinergic agent that acts to inhibit the ability of the pupil to constrict and an alpha-agonist agent that acts to stimulate the ability of the pupil to dilate. These agents may be used alone or in combination. For patients whose pupils have at least partially dilated by NIR illumination and/or limiting light exposure, the application of an alpha-agonist may be sufficient to augment dilation for fundus image acquisition. For example, one drop of an alpha-agonist such as 2.5% phenylephrine may help encourage further pupillary dilation beyond the non- mydriatic dilation that may have already occurred by using the glasses described above.

Reducing the number of pharmacological agents and/or their dose may also help reduce the amount of time the pupil remains dilated after the examination. For this reason, non-mydriatic dilation that has been augmented with a relatively lower dose of pharmacological agent(s) may be preferred over traditional mydriatic dilation with a full dose of pharmacological agent(s). It should be understood that the systems and methods described herein may also be used to acquire fundus images in conjunction with mydriatic pupil dilation.

[0054] FIG. 9B is a flowchart representation of one variation of a method for acquiring non- mydriatic images of an eye (e.g., the fundus of the eye). The method (910) may comprise illuminating (912) a patient's eye using a NIR light source of a detachable imaging system coupled to a portable computing device, activating (914) the visible light source of the portable imaging device to deactivate the NIR light source, illuminating (916) the patient's eye with a visible light pulse from the visible light source, and acquiring (918) an image of the patient's eye using the image sensor of the portable computing device. The time duration between visible light illumination and image acquisition may be sufficiently short (e.g., about 0.5 second or less) so that the image is acquired while the pupil is dilated (e.g., before the pupil constricts substantially). The detachable imaging system may be any of the detachable imaging systems described herein. For example, the detachable imaging system may comprise a control circuit comprising a light-dependent resistor that controls activation of the NIR light source according to light output from the visible light source of the portable computing device. Activating the visible light source may change a resistance value of the light-dependent resistor, and such change may deactivate the NIR light source, as described previously. The portable imaging system may comprise a light guide or emitter, such as a fiber optic cable, that is optically connected to the visible light source of the portable computing device and may channel a portion of the visible light output to the light-dependent resistor of the control circuitry and a portion of the visible light output to an optical lens assembly for illuminating the eye. The visible light from the portable computing device may be a short light pulse (e.g., less than about 0.5 second) so that the pupil does not constrict substantially as the image is being acquired. The method (910) may optionally comprise acquiring additional images of the eye which may comprise after waiting (920) about 5 seconds to about 8 seconds after the first visible light illumination/pulse, activating the visible light source and illuminating (922) the eye for a second time, and acquiring (924) a second image of the eye. The time duration between visible light illumination and image acquisition may be sufficiently short (e.g., about 0.5 second or less) so that the image is acquired while the pupil is dilated (e.g., before the pupil constricts substantially). During the waiting period, the eye may optionally be illuminated with NIR light, dim light, and/or no illumination may be provided at all.

[0055] Although particular embodiments or variations of the present inventions have been shown and described, it will be understood that it is not intended to limit the present inventions to the disclosed embodiments, and it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present inventions. Thus, the present inventions are intended to cover alternatives, modifications, and equivalents, which may be included within the spirit and scope of the present inventions as defined by the claims.

Claims

1. A detachable imaging system for acquiring non-mydriatic images of an eye using a portable computing device, the system comprising: an optical lens assembly; a light emitter optically connected to the optical lens assembly to provide illumination to the optical lens assembly; a first light source optically connected to the optical lens assembly; and control circuitry in electrical communication with the first light source, the control circuitry comprising a light-dependent resistor positioned adjacent to the light emitter and configured to control activation of the first light source by changing a resistance value of the light-dependent resistor according to light output from the light emitter.

2. The system of claim 1 , wherein the light emitter comprises a fiber optic cable configured to optically connect a second light source with the optical lens assembly.

3. The system of claim 1 , wherein the first light source emits near-infrared or red wavelength light.

4. The system of claim 3, wherein the first light source comprises a light-emitting diode.

5. The system of claim 1 , wherein when light output from the light emitter is at or below a predetermined illumination threshold, the resistance value of the light-dependent resistor increases and causes activation of the first light source.

6. The system of claim 5, wherein when light output from the light emitter increases above the pre-determined illumination threshold, the resistance value of the light-dependent resistor decreases and causes deactivation of the first light source.

7. The system of any one of claims 1 -6, further comprising a first beam splitter in optical connection with the light emitter and the first light source, wherein the first beam splitter has a transmission to reflectance ratio of at least about 60:40 such that a greater proportion of light from the light emitter is transmitted to the optical lens assembly than is reflected from the first light source to the optical lens assembly.

8. The system of claim 1 , wherein the light emitter emits visible wavelength light.

9. The system of claim 2, wherein the second light source comprises a light source of a portable computing device.

10. The system of any one of claims 1-9, further comprising an optical lens assembly housing that encloses the optical lens assembly, and a portable computing device case configured to releasably couple to a portable computing device, wherein the light emitter, first light source, and control circuitry are mounted to the portable computing device case, and the optical lens assembly housing is configured to be releasably attached to the portable computing device case.

1 1. The system of claim 10, wherein the light emitter comprises a fiber optic cable comprising a first end and a second end, and the portable computing device case comprises a first optically- opaque enclosure disposed over the first end of the cable and a second optically-opaque enclosure disposed over the second end of the cable.

12. The system of claim 7, wherein the optical lens assembly comprises a collector lens configured to receive light from the light emitter and the first light source, a first polarizing filter configured to transmit light from the collector lens having a first orientation, a second beam splitter that is configured to reflect light from the first polarizing filter having the first orientation and configured to transmit light having a second orientation that is opposite to the first orientation, an objective lens, a second polarizing filter configured to transmit light from the objective lens having the second orientation, and a relay lens that transmits light from the second polarizing filter to an image sensor of a portable computing device.

13. The system of any one of claims 1-12, wherein the optical lens assembly is configured to provide illumination light with along an illumination axis to an illumination focal point in an eye, and to receive light along an imaging axis, and wherein the illumination axis is offset from the imaging axis.

14. The system of claim 12, wherein the second beam splitter has a first central axis and the relay lens has a second central axis, wherein the first central axis is offset from the second central axis.

15. The system of claim 14, wherein the first central axis is offset by about 1.25 mm from the second central axis.

16. The system of claim 12, wherein the objective lens is retained within an objective lens mount, and wherein the optical lens assembly housing comprises an attachment region with a plurality of threaded protrusions, and the objective lens mount comprises a receiving region with a plurality of threaded grooves that correspond with the threaded protrusions.

17. A method for acquiring non-mydriatic images of an eye using a portable computing device, the method comprising: illuminating a patient's eye with a near-infrared light source of an imaging system coupled to a portable computing device, wherein the portable computing device comprises a visible light source and an image sensor, and wherein the imaging system further comprises control circuitry comprising a light-dependent resistor that controls activation of the near- infrared light source according to light output from the visible light source of the portable computing device; activating the visible light source of the portable computing device to change a resistance value of the light-dependent resistor and deactivate the near-infrared light source; illuminating the patient's eye with the visible light source of the portable computing device; and acquiring an image of the patient's eye using the image sensor of the portable computing device.

18. The method of claim 17, wherein the imaging system further comprises a fiber optic cable that optically connects the visible light source of the portable computing device and the light- dependent resistor such that light from the visible light source illuminates the light-dependent resistor.

19. The method of claim 18, wherein the imaging system further comprises an optical lens assembly comprising a collector lens configured to receive light from the fiber optic cable and the near-infrared light source, a first polarizing filter configured to transmit light from the collector lens having a first orientation, a second beam splitter that is configured to reflect light from the first polarizing filter having the first orientation and configured to transmit light having a second orientation that is opposite to the first orientation, an objective lens, a second polarizing filter configured to transmit light from the objective lens having the second orientation, and a relay lens that transmits light from the second polarizing filter to the image sensor of the portable computing device.

20. The method of claim 19, further comprising adjusting an optical path length between the objective lens and the relay lens to mitigate patient refractive errors before illuminating the patient's eye with the visible light source of the portable computing device.

21. The method of claim 17, wherein illuminating the patient's eye with the visible light source of the portable computing device comprises illuminating the patient's eye with visible wavelength light for less than about 0.5 second.

22. The method of claim 21 , wherein visible wavelength light comprises white light.

23. The method of claim 18, wherein activating the visible light source comprises increasing light output from the fiber optic cable above a pre-determined illumination threshold causes the resistance value of the light-dependent resistor to decrease and deactivate the near-infrared light source.

24. The method of claim 23, wherein when the light output from the fiber optic cable is at or below the pre-determined illumination threshold, the resistance value of the light-dependent resistor to increases and activates the near-infrared light source.

25. The method of claim 17, wherein the portable computing device comprises a smartphone.

26. The method of claim 19, wherein illuminating the patient's eye comprises providing illumination light with along an illumination axis to an illumination focal point in the eye, and acquiring an image of the patient's eye comprises receiving light by the image sensor along an imaging axis, wherein the illumination axis is offset from the imaging axis.

27. The method of claim 26, wherein the illumination axis is offset from the imaging axis by about 1.25 mm.

28. The method of claim 17, further comprising disposing a pair of glasses over the patient's eyes, the glasses comprising color-tinted filtered lenses that transmit light having a wavelength longer than about 580 nm, and frames that retain the lenses, wherein the frames comprise one or more side, top, and/or bottom light-blocking flaps to simulate a low-light environment for the patient.

29. A kit for acquiring non-mydriatic images of an eye, the kit comprising: a portable computing device comprising a camera having an image sensor and a visible light source; and an imaging device configured to be coupled to the portable computing device, the imaging device comprising an optical lens assembly, a near-infrared light source that is optically connected to the optical lens assembly, and a control circuit that is electrically connected to the near-infrared light source and optically connected to the portable computing device image sensor.

30. The kit of claim 29, wherein the control circuit comprises a light-dependent resistor and the detachable imaging device further comprises a fiber optic cable having a first light-receiving portion optically connected to the portable computing device visible light source and an illumination portion adjacent to the light-dependent resistor.

31. The kit of claim 30, wherein the near-infrared light source is connected to the control circuit such that activation of the near-infrared light source is controlled by changing a resistance value of the light-dependent resistor according to light output from the illumination portion of the fiber optic cable.

32. The kit of any one of claims 29-31, further comprising a pair of glasses comprising color- tinted filtered lenses that selectively transmits light having a wavelength longer than about 580 nm and frames that retain the lenses, wherein the frames comprise one or more side, top, and/or bottom light-blocking flaps.

33. The kit in any one of claims 29-32, further comprising a fluorescence imaging device configured to be coupled to the portable computing device, the fluorescence imaging device comprising an optical lens assembly, an ultraviolet light source that is optically connected to the optical lens assembly, and a control circuit that is electrically connected to the ultraviolet light source and optically connected to the portable computing device image sensor.

34. The kit in any one of claims 29-33, further comprising an auto-fluorescence imaging device configured to be coupled to the portable computing device, the auto-fluorescence imaging device comprising an optical lens assembly, a blue or green light source that is optically connected to the optical lens assembly, and a control circuit that is electrically connected to the blue or green light source and optically connected to the portable computing device image sensor.