Patent Publication Number: US-11642017-B2

Title: Methods and apparatus for making a determination about an eye in ambient lighting conditions

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of U.S. patent application Ser. No. 16/250,592 filed Jan. 17, 2019, which will issue as U.S. Pat. No. 10,986,991 on Apr. 27, 2021, which is a continuation application of U.S. patent application Ser. No. 14/934,742 filed Nov. 6, 2015, now U.S. Pat. No. 10,219,687 issued Mar. 5, 2019, which claims priority to and benefit of U.S. provisional patent application Ser. No. 62/076,804 filed Nov. 7, 2014, each of which are fully incorporated by reference and made parts hereof. 
    
    
     BACKGROUND 
     There are many existing devices that are used to detect the optical quality of the eye or other optical systems, including: autorefractors/ophthalmic refractometers, aberrometers, etc. All of the existing devices work by using a light source to illuminate the eye. Many devices, including the vast majority of autorefractors, use an infrared light source, but visible light sources are also used. Anyone who has used a standard camera with a flash will know that light from the flash will reflect off of the retina during photography. This reflected light will make the pupil appear red in a photograph of a human eye or appear greenish in a photograph of many animals&#39; eyes. The reflected light will also have a particular pattern that is dependent upon the eye&#39;s optical distortions. Many existing/previous autorefractors or aberrometers are based on this principle, i.e., shining a light into the eye and then detecting the pattern of the reflected light after it has been distorted by the eye. The devices vary in the configuration or type of light source or in how the reflected light is detected (single images, lenslet arrays, telescope combined with a lenslet array, etc.). However, in each of those cases, a light is shined into the eye and then the magnitude of the refractive error is determined, and this is often based on the intensity slope of the light (brighter at either the top or the bottom of the pupil) that is reflected off of the retina and back out of the eye. 
     Therefore, methods, apparatus and systems are desired that improve the detection of an optical quality of the eye or other optical system and that overcome challenges in the art, some of which are described above. 
     SUMMARY 
     Described herein are devices and methods to measure optical distortions in the eye by monitoring the intensity of a first color of light versus intensity of a second color of light within the pupil of a subject under ambient lighting conditions, which is readily available light where no emitter of light is shined into the eye. For example, although there may be lamps and light fixtures in a room wherein devices and methods described in this disclosure are practiced, these sources or emitters of light are not used purposefully to illuminate the eye and the source of light is not directed into the eye. The subject can be a human or an animal. While the pupil may appear to be black or very dark in a photograph that does not use a flash, the pixel values do vary in magnitude based on the power of the eye. In the images that are obtained for embodiments of this invention, the information needed to measure the optical distortions of the eye is contained within the pixel values of the first and second color. 
     Non-relevant reflections from the lens and corneal surface are blocked; else these reflections would otherwise obscure measurement of the light within the pupil. For example, the surface closest to the patient of the apparatus acquiring the images can be matte and black so that it does not create corneal reflections that would obscure the measurement, or a polarizing filter can be used. 
     Once this image is obtained, the pupil and its border are identified. Light within the pupil is then analyzed. No light is shined into the eye. The total intensity of the pupil is used in a formula that calculates the autorefraction result, and a minimum intensity is required, but differences in intensity across the pupil are not measured for autorefraction. The light in an eye with spherical refractive error does not have a slope; it is of uniform intensity within the pupil. Even the difference between the pixels of the first color and the second color is uniform across the pupil for spherical refractive error (i.e., no astigmatism). Ambient light from the room that is always reflecting off of the retina is measured. A difference in the intensity of the first color versus the second color pixel values is determined and compared; this difference is related to the eye&#39;s refractive error/glasses prescription. For example, the difference between the first color and second color pixels is a larger number in hyperopia (farsighted) and a lower number in myopia (nearsighted). Also, the light within the pupil of eyes with hyperopia is somewhat brighter than eyes with myopia. In the case of astigmatism, the intensity of individual pixels across the pupil will have a higher standard deviation than with hyperopia or myopia alone. In most eyes, the axis of the astigmatism is known to be regular, meaning that the two principal power meridians are 90 degrees apart. In the present disclosure, the presence of astigmatism within an optical system causes differences in intensity within the pupil. The more myopic meridian will be dimmer and the more hyperopic meridian will be brighter. 
     Disclosed herein is a method of making a determination about an eye. The method comprises detecting, using a computing device, ambient light reflected out of an eye of a subject from a retina of the eye of the subject; and making a determination about the eye of the subject based upon the reflected ambient light. As described herein, the reflected light relies upon ambient light and no additional light emitter is required or directed toward the eye to create the reflected light. The determination about the eye is made based at least in part on an aspect of the reflected ambient light. For example, overall brightness and the intensity of one or more colors of the reflected ambient light can be used to make the determination about the eye. 
     In one aspect, the determination made about the eye comprises the refractive error for the eye of the subject based at least in part on an aspect of the reflected ambient light. 
     Alternatively, or optionally, in reference to the above-described method, detecting, using the computing device, ambient light reflected out of an eye of a subject from a retina of the eye of the subject can further comprise capturing, using an image capture device, an image of the eye of a subject, wherein the image is captured using only ambient lighting conditions and wherein non-relevant reflections from the eye of the subject are managed while capturing the image; determining, using the computing device, an overall intensity of light from a plurality of pixels located within the at least a portion of a pupil captured in the image; determining, using the computing device, a first intensity of a first color from the plurality of pixels located within the at least a portion of a pupil of the eye of the subject captured in the image; determining, using the computing device, a second intensity of a second color from the plurality of pixels located within the at least a portion of the pupil of the eye of the subject captured in the image; and comparing, by the computing device, a relative intensity of the first color and a relative intensity of the second color, wherein the comparison and the overall intensity are used to make the determination about the eye of the subject based upon the reflected ambient light. Either the first or the second color can be any one or any combination of red green and blue. 
     In one aspect, the above described method can be used to make determinations about the eye that include an autorefraction or a photorefraction measurement. For example, capturing, using the image capture device, an image of the eye of the subject can comprise capturing a first image using only ambient lighting conditions with the image capture device through a spectacle lens or a contact lens while the subject is wearing the spectacle lens or the contact lens over the eye and capturing a second image using only ambient lighting conditions with the image capture device while the subject is not wearing the spectacle lens or the contact lens over the eye and the first image is compared to the second image and the determination about the eye of the subject based upon the reflected ambient is based on the comparison and comprises an estimated prescription for the spectacle lens or the contact lens. 
     Alternatively, or optionally, in reference to the above-described method, when the first intensity of the first color is brighter relative to the second intensity of the second color and the overall intensity is relatively brighter, the determination about the eye of the subject based upon the reflected ambient light comprises a positive value or hyperopia. Similarly, when the first intensity of the first color is dimmer relative to the second intensity of the second color and the overall intensity is relatively dimmer, the determination about the eye of the subject based upon the reflected ambient light comprises a negative value or myopia. 
     The above-described method can also be used to make a determination about the eye such as astigmatism. For example, the method can further comprise making a first determination about the eye of the subject based upon the reflected ambient light from a first plurality of pixels located within the at least a portion of the pupil of the eye of the subject captured in the image; making a second determination from a second plurality of pixels located within the at least a portion of the pupil of the eye of the subject captured in the image, wherein the second plurality of pixels are a subset of the first plurality of pixels; making a third determination from a third plurality of pixels located within the at least a portion of the pupil of the eye of the subject captured in the image, wherein the third plurality of pixels are a subset of the first plurality of pixels and are separate from the second plurality of pixels; and comparing the first determination, the second determination and the third determination to make the determination about the eye of the subject based upon the reflected ambient light. Comparing the first determination, the second determination and the third determination to make the determination about the eye of the subject based upon the reflected ambient light can comprise one or more of determining a standard deviation of the first determination to the second determination, a standard deviation of the first determination to the second determination, or a standard deviation of the second determination to the third determination, wherein the determined standard deviation indicates the determination about the eye of the subject based upon the reflected ambient light. As noted above, the determination about the eye of the subject based upon the reflected ambient light can be a presence or an absence of astigmatism. Further, when the presence of astigmatism is detected, an amount of astigmatism can be determined by comparing the overall intensity and the relative intensity of the first color or the relative intensity of the second color of various regions of the pupil. 
     As noted above, the method comprises managing non-relevant reflections from the eye while capturing the image. Generally, this comprises managing reflections from a cornea or a lens of the eye of the subject while capturing the image. For example, managing non-relevant reflections from the eye while capturing the image can comprise placing a polarizing filter over a lens of the image capture device or between the image capture device and the eye of the subject. Alternative or optionally, managing non-relevant reflections from the eye while capturing the image can comprise blocking light that would lead to reflections from a corneal surface of the eye or a lens of the eye. For example, managing non-relevant reflections from the eye while capturing the image can comprise providing a surface that absorbs light or prevents the non-relevant reflections from the eye while capturing the image. The surface can have a black matte finish. In one aspect, the surface can comprise a portion of the image capture device. For example, the surface can comprise at least a portion of a case that houses the image capture device. 
     In reference to the above-described method, the image capture device can comprise a smart phone or other mobile computing device having a camera. Generally, the image capture device can capture a still image or a video of the eye of the subject. 
     The above-described method can be used to make a determination about the eye of a person having a smaller than average pupil. For example, where the subject&#39;s pupil has a diameter of approximately 2 mm or less. Further, the subject&#39;s pupil can be a natural pupil or an artificial pupil. The eye of the subject can be the subject&#39;s left eye or right eye, or the subject&#39;s left eye and right eye. In one aspect, the method can further comprise detecting an intensity for the ambient light conditions and providing an indication if the ambient light conditions are too low for the image capture device to capture the image of the eye of the subject. 
     Also disclosed herein is an alternate method of making a determination about an eye. The method comprises capturing, using an image capture device, an image of an eye of a subject, wherein the image is captured using only ambient lighting conditions and wherein non-relevant reflections from a cornea and a lens of the eye of the subject are managed while capturing the image; determining, using a computing device, an overall intensity of light from a plurality of pixels located within at least a portion of a pupil captured in the image, wherein the plurality of pixels comprise red, green and blue pixels; determining, using the computing device, an average red intensity from the plurality of pixels located within the at least a portion of the pupil captured in the image; determining, using the computing device, an average blue intensity from the plurality of pixels located within the at least a portion of a pupil captured in the image; and determining, by the computing device, using the average red intensity, the average blue intensity and the determined overall intensity an optical quality of the eye. 
     Similarly as described above, the determined optical quality of the eye can comprise an autorefraction or photorefraction measurement such that the method can be used to provide an estimated prescription for spectacle lens or contact lens. Further, the method can be used to determine an optical quality of the eye such as a positive value or hyperopia, a negative value or myopia, the presence or absence of astigmatism, and an amount of astigmatism if is found to be present. 
     Another aspect of the disclosure is an apparatus for performing the above-described methods. In one embodiment, the apparatus comprises an image capture device; a memory; and a processor in communication with the memory and the image capture device, wherein the processor executes computer-readable instructions stored in the memory that cause the processor to: capture, using the image capture device, an image of an eye of a subject, wherein the image is captured using only ambient lighting conditions and wherein non-relevant reflections from the eye of the subject are managed while capturing the image; detect, from the image of the eye of the subject, ambient light reflected out of the eye of a subject from a retina of the eye of the subject; and make a determination about the eye of the subject based upon the detected reflected ambient light. 
     In one aspect, the determination made about the eye by the apparatus comprises the refractive error for the eye of the subject based at least in part on an aspect of the reflected ambient light. 
     Alternatively, or optionally, the apparatus can be used for detecting ambient light reflected out of an eye of a subject from a retina of the eye of the subject by determining an overall intensity of light from a plurality of pixels located within the at least a portion of a pupil captured in the image; determining a first intensity of a first color from the plurality of pixels located within the at least a portion of a pupil of the eye of the subject captured in the image; determining a second intensity of a second color from the plurality of pixels located within the at least a portion of the pupil of the eye of the subject captured in the image; and comparing a relative intensity of the first color and a relative intensity of the second color, wherein the comparison and the overall intensity are used to make the determination about the eye of the subject based upon the reflected ambient light. Either the first or the second color can be any one or any combination of red green and blue. 
     In one aspect, the above described apparatus can make determinations about the eye that include an autorefraction or a photorefraction measurement. For example, when capturing, using the image capture device, an image of the eye of the subject the processor can execute computer-readable instructions store in the memory to capture a first image using only ambient lighting conditions with the image capture device through a spectacle lens or a contact lens while the subject is wearing the spectacle lens or the contact lens over the eye and capture a second image using only ambient lighting conditions with the image capture device while the subject is not wearing the spectacle lens or the contact lens over the eye and the first image is compared to the second image and the determination about the eye of the subject based upon the reflected ambient is based on the comparison and comprises an estimated prescription for the spectacle lens or the contact lens. 
     Alternatively, or optionally, the processor of the apparatus can execute computer-readable instructions such that when the first intensity of the first color is brighter relative to the second intensity of the second color and the overall intensity is relatively brighter, the determination about the eye of the subject based upon the reflected ambient light comprises a positive value or hyperopia. Similarly, when the first intensity of the first color is dimmer relative to the second intensity of the second color and the overall intensity is relatively dimmer, the determination about the eye of the subject based upon the reflected ambient light comprises a negative value or myopia. 
     The above-described apparatus can also be used to make a determination about the eye such as astigmatism. For example, the processor of the apparatus can execute computer-readable instructions for making a first determination about the eye of the subject based upon the reflected ambient light from a first plurality of pixels located within the at least a portion of the pupil of the eye of the subject captured in the image; making a second determination from a second plurality of pixels located within the at least a portion of the pupil of the eye of the subject captured in the image, wherein the second plurality of pixels are a subset of the first plurality of pixels; making a third determination from a third plurality of pixels located within the at least a portion of the pupil of the eye of the subject captured in the image, wherein the third plurality of pixels are a subset of the first plurality of pixels and are separate from the second plurality of pixels; and comparing the first determination, the second determination and the third determination to make the determination about the eye of the subject based upon the reflected ambient light. Comparing the first determination, the second determination and the third determination to make the determination about the eye of the subject based upon the reflected ambient light can comprise one or more of determining a standard deviation of the first determination to the second determination, a standard deviation of the first determination to the second determination, or a standard deviation of the second determination to the third determination, wherein the determined standard deviation indicates the determination about the eye of the subject based upon the reflected ambient light. As noted above, the determination about the eye of the subject based upon the reflected ambient light can be a presence or an absence of astigmatism. Further, when the presence of astigmatism is detected, an amount of astigmatism can be determined by comparing the overall intensity and the relative intensity of the first color or the relative intensity of the second color of various regions of the pupil. 
     As noted above, the apparatus can manage non-relevant reflections from the eye while capturing the image. Generally, this comprises managing reflections from a cornea or a lens of the eye of the subject while capturing the image. For example, managing non-relevant reflections from the eye while capturing the image can comprise placing a polarizing filter over a lens of the image capture device or between the image capture device and the eye of the subject. Alternative or optionally, managing non-relevant reflections from the eye while capturing the image can comprise blocking light that would lead to reflections from a corneal surface of the eye or a lens of the eye. For example, managing non-relevant reflections from the eye while capturing the image can comprise providing a surface that absorbs light or prevents the non-relevant reflections from the eye while capturing the image. The surface can have a black matte finish. In one aspect, the surface can comprise a portion of the image capture device. For example, the surface can comprise at least a portion of a case that houses the image capture device. 
     In reference to the above apparatus, the image capture device can comprise a smart phone or other mobile computing device having a camera. Generally, the image capture device can capture a still image or a video of the eye of the subject. 
     The above-described apparatus can be used to make a determination about the eye of a person having a smaller than average pupil. For example, where the subject&#39;s pupil has a diameter of approximately 2 mm or less. Further, the subject&#39;s pupil can be a natural pupil or an artificial pupil. The eye of the subject can be the subject&#39;s left eye or right eye, or the subject&#39;s left eye and right eye. In one aspect, the apparatus can further comprise a light meter to detect an intensity for the ambient light conditions and provide an indication if the ambient light conditions are too low for the image capture device to capture the image of the eye of the subject. 
     It should be understood that the above-described subject matter may also be implemented as a computer-controlled apparatus, a computer process, a computing system, or an article of manufacture, such as a computer-readable storage medium. 
     Other systems, methods, features and/or advantages will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be protected by the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The components in the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding parts throughout the several views. 
         FIG.  1    illustrates an exemplary overview apparatus for making a determination about the eye of a subject in ambient lighting conditions; 
         FIG.  2 A  illustrates an example of an apparatus for capturing an image of the eye and making a determination about an eye in ambient lighting conditions; 
         FIG.  2 B  illustrates an image of the eye captured by an apparatus for capturing an image of the eye and making a determination about an eye in ambient lighting conditions; 
         FIG.  2 C  illustrates an example of an apparatus for capturing an image of the eye and making a determination about an eye in ambient lighting conditions; 
         FIG.  2 D  illustrates an image of an eye that can be used to make a determination about the eye such as astigmatism; 
         FIG.  2 E  illustrates an example of an apparatus for capturing an image of the eye using polarizing filters and making a determination about an eye in ambient lighting conditions; 
         FIG.  2 F  illustrates an example of an apparatus for capturing an image of the eye using a surface and making a determination about an eye in ambient lighting conditions; 
         FIG.  3    illustrates an example computing device upon which embodiments of the invention may be implemented; 
         FIG.  4    illustrates an example method for making a determination about an eye of a subject based upon ambient light reflected out of the eye; and 
         FIG.  5    illustrates an alternate example method for making a determination about an eye of a subject based upon ambient light reflected out of the eye. 
     
    
    
     DETAILED DESCRIPTION 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure. 
     As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. 
     “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. 
     Throughout the description and claims of this specification, the word “comprise” and variations of the word, such as “comprising” and “comprises,” means “including but not limited to,” and is not intended to exclude, for example, other additives, components, integers or steps. “Exemplary” means “an example of” and is not intended to convey an indication of a preferred or ideal embodiment. “Such as” is not used in a restrictive sense, but for explanatory purposes. 
     Disclosed are components that can be used to perform the disclosed methods and systems. These and other components are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these components are disclosed that while specific reference of each various individual and collective combinations and permutation of these may not be explicitly disclosed, each is specifically contemplated and described herein, for all methods and systems. This applies to all aspects of this application including, but not limited to, steps in disclosed methods. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific embodiment or combination of embodiments of the disclosed methods. 
     The present methods and systems may be understood more readily by reference to the following detailed description of preferred embodiments and the Examples included therein and to the Figures and their previous and following description. 
       FIG.  1    illustrates an exemplary overview apparatus for making a determination about the eye of a subject in ambient lighting conditions. As shown in  FIG.  1   , one embodiment of the apparatus  100  comprises an image capture mechanism  102 . In one aspect, the image capture mechanism  102  can be camera. The image capture mechanism  102  can take still and/or video images. Generally, the image capture mechanism  102  will be a digital camera, but can be an analog device equipped with or in communication with an appropriate analog/digital converter. The image capture mechanism  102  may also be a webcam, scanner, recorder, or any other device capable of capturing a still image or a video. 
     In one aspect, the image capture mechanism  102  is in direct communication with a computing device  110  through, for example, a network (wired (including fiber optic), wireless or a combination of wired and wireless) or a direct-connect cable (e.g., using a universal serial bus (USB) connection, IEEE 1394 “Firewire” connections, and the like). In other aspects, the image capture mechanism  102  can be located remotely from the computing device  110 , but capable of capturing an image and storing it on a memory device such that the image can be downloaded or transferred to the computing device  110  using, for example, a portable memory device and the like. In one aspect, the computing device  110  and the image capture mechanism  102  can comprise or be a part of a device such as a smart phone, table, laptop computer or any other mobile computing device. 
     In a basic configuration, the computing device  110  can be comprised of a processor  104  and a memory  108 . The processor  104  can execute computer-readable instructions that are stored in the memory  108 . Moreover, images captured by the image capture device  102 , whether still images or video, can be stored in the memory  108  and processed by the processor  104  using computer-readable instructions stored in the memory  108 . 
     The processor  104  is in communication with the image capture device  102  and the memory  108 . The processor  104  can execute computer-readable instructions stored on the memory  108  to capture, using the image capture device  102 , an image of an eye  106  of a subject. No light source, other than ambient lighting, is required to capture the image. The image is captured using only ambient lighting conditions and does not require an additional light source to be directed into the eye  106 . While capturing the image of the eye  106 , non-relevant reflections from the eye  106  of the subject are managed. 
     The processor  104  can further execute computer-readable instructions stored on the memory  108  to detect, from the image of the eye  106  of the subject, ambient light reflected out of the eye  106  of the subject from the retina of the eye  106  of the subject and to make a determination about the eye  106  of the subject based upon the detected reflected ambient light. Generally, the processor  104  of the apparatus  100  executing computer-readable instructions stored in the memory  108  that cause the processor  104  to make a determination about the eye  106  of the subject based at least in part on an aspect of the reflected ambient light. Such aspects can include, for example, an overall brightness or intensity of the reflected ambient light as determined in a plurality of pixels of the image acquired by the image capture device  102 . The aspects can also include one or more colors of the reflected ambient light also as determined from the plurality of pixels of the image acquired by the image capture device  102 . For example, the processor  104  executing computer-readable instructions stored in the memory  108  can cause the processor  104  to make a determination about the eye  106  based at least in part on the overall brightness or intensity of the red, green and blue pixels that comprise the reflected ambient light as determined from the image acquired by the image capture device. Overall brightness can be determined, as a non-limiting example, using methods and software developed by Allan Hanbury (see, for example, “A 3D-Polar Coordinate Colour Representation Well Adapted to Image Analysis,” Hanbury, Allan; Vienna University of Technology, Vienna, Austria, 2003), which is fully incorporated herein by reference and made a part hereof. The processor  104  also uses the relative intensity of red, green or blue found in the plurality of pixels of the image acquired by the image capture device  102  to make the determination about the eye  106 . For example, using at least in part on an aspect of the reflected ambient light as determined from an image of the eye  106  as captured by the image capture device  102 , the processor  104  executing computer-readable instructions stored in the memory  108  can make determinations about the eye  106  comprising a refractive error for the eye  106  of the subject. In other words, using at least in part an overall brightness or intensity of the reflected ambient light as determined in a plurality of the pixels of the image acquired by the image capture device  102  and the relative intensity of one or more colors of the reflected ambient light also as determined from the plurality of pixels of the image acquired by the image capture device  102 , the processor  104  executing computer-readable instructions stored in the memory  108  can make determinations about the eye  106  including a refractive error for the eye  106  of the subject. 
     As shown in  FIG.  2 A , the image capture device  102  of the apparatus  100  captures an image ( FIG.  2 B )  208  of the eye  106 . The processor  104  of the apparatus  100  can execute computer-readable instructions stored in the memory  108  that cause the processor  104  to detect, from the image  208  of the eye, ambient light  202  reflected  204  out of an eye  106  of the subject from the retina  206  of the eye  106  of the subject and determine the overall intensity of the plurality of pixels (example pixels are shown in  FIG.  2 B  as white “x” in the pupil  210  of the image  208  of the eye) within the pupil  210  or a portion of the pupil  210 ; determine an intensity of a first color from a the plurality of pixels located within the pupil  210  or at least a portion of a pupil  210  of the eye of the subject captured in the image  208 ; determine an intensity of a second color from the plurality of pixels located within the pupil  201  or at least a portion of the pupil  210  of the eye of the subject captured in the image  208 ; and calculate refractive error or glasses prescription based on regression analysis. The regression analysis includes at least one of the following elements (1) the overall intensity or brightness of the pixels within pupil  210  or a portion of the pupil  210 ; and (2) the relative intensity of a first color from a first one or more pixels located within at least a portion of a pupil  210  of the eye of the subject captured in image  208  as compared to a second color from a second one or more pixels located within the at least a portion of the pupil  210  of the eye of the subject captured in image  208 . Optionally, the regression analysis can also include (3) the color of the iris of the subject captures in image  208 ; and (4) the overall intensity of the ambient lighting at the time the image is captured with the image capturing device  100 . For example, when the intensity of the first color is brighter relative to the intensity of the second color and the overall intensity is relatively brighter, the determination about the eye of the subject based upon the reflected ambient light can comprise a positive value or hyperopia. Alternatively, when the intensity of the first color is dimmer relative to the intensity of the second color and the overall intensity is relatively dimmer, the determination about the eye of the subject based upon the reflected ambient light can comprise a negative value or myopia. 
     For example, the first color can comprise any one or any combination of red, green, and blue and the second color can comprise any one or combination of red, green, and blue that is not used as the first color. 
     By performing the steps described above, the processor  104  of the apparatus  100  can execute computer-readable instructions stored in the memory  108  that cause the processor  104  to make an autorefraction or a photorefraction measurement. For example, as shown in  FIG.  2 C , the apparatus  100  can capture, using the image capture device  102 , an image  208  of the eye  106  of the subject using only ambient lighting  202  conditions through a spectacle lens or a contact lens (both shown as  212  in  FIG.  2 C ) while the subject is wearing the spectacle lens or the contact lens  212  over the eye  106 . The image capturing device  102  of the apparatus  100  then captures a second image using only ambient lighting  202  conditions while the subject is not wearing the spectacle lens or the contact lens  212  over the eye (see, for example,  FIG.  2 A ) and the processor  104  executes computer-readable instructions stored in the memory  108  that cause the processor  104  to compare the first image to the second image and the determination about the eye of the subject based upon the reflected  204  ambient light is based on the comparison and comprises an estimated prescription for the spectacle lens or the contact lens  212 . 
     Referring now to  FIG.  2 D , in yet another aspect, the processor  104  can execute computer-readable instructions stored in the memory  108  that cause the processor  104  to make a first determination about the eye  106  of the subject based upon the reflected ambient light from a first plurality of pixels  220  located within the at least a portion of the pupil  210  of the eye  106  of the subject captured in the image  208 ; make a second determination from a second plurality of pixels  222  located within the at least a portion of the pupil  210  of the eye  106  of the subject captured in the image  208 , wherein the second plurality of pixels  222  are a subset of the first plurality of pixels  210 ; make a third determination from a third plurality of pixels  224  located within the at least a portion of the pupil  210  of the eye  106  of the subject captured in the image  208 , wherein the third plurality of pixels  224  are a subset of the first plurality of pixels  210  and are separate from the second plurality of pixels  222 ; and compare the first determination, the second determination and the third determination to make the determination about the eye  106  of the subject based upon the reflected ambient light. For example, comparing the first determination, the second determination and the third determination to make the determination about the eye  106  of the subject based upon the reflected ambient light can comprise one or more of determining a standard deviation of the first determination to the second determination, a standard deviation of the first determination to the second determination, or a standard deviation of the second determination to the third determination, wherein the determined standard deviation indicates the determination about the eye  106  of the subject based upon the reflected ambient light. The determination made about the eye  106  of the subject based upon the reflected ambient light can be the presence or absence of astigmatism. The amount of astigmatism, once detected, can be determined by comparing the overall intensity and the relative intensity of the first color or the relative intensity of the second color of various regions of the pupil. For example, measuring one or more of hyperopia or myopia at the various regions of the pupil using the apparatus  100 , as described herein, can be used to determine the amount of astigmatism present in the eye  106 . 
     Consider the following example, again referring to  FIG.  2 D . If a determination of the eyes using the methods and apparatus described herein on the central region of the pupil (entire white dashed circle)  220  for someone with myopia (Ex: −2.00) and no astigmatism, a value of −2.00 would also be obtained in the sub-regions at 90 degrees (solid square) 222 and 0 degrees (dashed square)  224 . If someone has astigmatism, a refractive error of −2.00 may be obtained if the whole pupil central region of the pupil (entire white dashed circle)  210  is analyzed using the methods and apparatus described herein, but if the sub-region at 90 degrees (solid square)  222  is analyzed and determined to have a refractive error of −1.00 and the sub-region at 0 degrees (dashed square)  224  is analyzed and determined to have a refractive error of −3.00, the standard deviation would be higher in the case of astigmatism where the sub-regions  222 ,  224  would be −1.00 and −3.00, respectively. Thus, a prescription for corrective lenses also needs to be −1.00 and −3.00 in those two sub-regions  222 ,  224 , rather than an overall −2.00 for the central pupil region  220 . These numbers are also just examples. They could be positive, negative, or both (one of each). Also, many sub-regions can be evaluated to make a determination about the eye. In this example the two sub-regions are at 90 degrees and 0 degrees, but they could be at any location throughout the pupil  210 . 
     As described herein, the apparatus  100  or the image capture device  102  can manage non-relevant reflections from a cornea and a lens of the eye  106  of the subject while capturing the image  208 . Such non-relevant reflections can affect the determination about the eye of the subject based upon the reflected ambient light. Managing the non-relevant reflections can include, for example and as shown in  FIG.  2 E , the use of a polarizing filter  214 , wherein non-relevant reflections  216  from the eye  106  are managed while capturing the image  208  by placing the polarizing filter  214  over a lens of the image capture device  102  or between the image capture device  102  and the eye  106  of the subject when capturing the image  208 . 
     In yet another aspect, as shown in  FIG.  2 F , the apparatus  100  can further comprise a surface  218 , wherein non-relevant reflections  216  from the eye  106  are managed while capturing the image  208  comprise the surface  218  absorbing light or preventing the non-relevant reflections  216  from the eye  106  while capturing the image  208 . For example, when acquiring the image  208  the apparatus  100  including the image capture device  102  can be placed close to the eye  106  such that non-relevant reflections  216  are minimized and those that do occur are absorbed or prevented by the surface  218 . For example, the apparatus  100  including the image capture device  102  can be placed from approximately 4 to 10 cm away from the eye  106  while capturing the image  208 , or the apparatus  100  including the image capture device  102  can be placed from approximately 8 to 9 cm away from the eye  106  while capturing the image  208 . The surface  218  can comprise, for example, a surface having a black matte finish to facilitate the absorption of ambient light and prevent of non-relevant reflections. The surface  218  can comprise a portion of the image capture device  102  or the apparatus  100 , including a case that may house at least a portion of the image capture device  102  or the apparatus  100 . For example, the image capture device  102  may comprise at least a portion of a smart phone or other mobile computing device having a camera and the surface  218  can be at least a portion of a case that houses the smart phone or other mobile computing device having a camera. 
     This disclosure contemplates apparatus that can be used make determinations about the eye  106  in eyes that have smaller than average pupil diameters such as, for example, approximately 2 mm or less. This is currently a challenge for many photorefractors that require assessing the slope of the reflected light over a wide pupil diameter, making it is less useful in more brightly lit rooms or in older patients who have smaller pupils. Further, embodiments of the apparatus described herein can monitor the reflected light in just the center region of the pupil in this measurement allowing accurate measurement of the smaller pupil. 
     Further, embodiments of the apparatus described herein can monitor the reflected light in a natural pupil or an artificial pupil. An artificial, or second pupil can be optically created for an eye by combining lenses and apertures, without placing anything inside the eye. Vision scientists regularly create what is called a Maxwellian View during experiments where they want to give all subjects the same pupil size by creating an artificial pupil. An artificial pupil could be optically created or physically created by placing an aperture in front of the eye. 
     Alternatively or optionally, the apparatus  100  as described herein can be used to make a determination of the subject&#39;s left eye or right eye. Similarly, it can be used to make a determination of the subject&#39;s left eye and right eye. 
     Though not shown in  FIG.  1   , the apparatus  100  can optionally include a light meter or any other mechanism for measure ambient lighting levels. The light meter can detect an intensity for the ambient light conditions and provide an indication if the ambient light conditions are too low for the apparatus  100  to capture an image of the eye of the subject based upon the reflected ambient light. In another aspect, the light meter can measure ambient lighting conditions and such measurement can be used to adjust the image or the calculation of refractive error using regression analysis accordingly. 
     When the logical operations described herein are implemented in software, the process may execute on any type of computing architecture or platform. Such a computing device  300  as shown in  FIG.  3    can be the same as computing device  110 , described above, or used alternatively for computing device  110 . For example, referring to  FIG.  3   , an example computing device  300  upon which embodiments of the invention may be implemented is illustrated. The computing device  300  can optionally be a mobile computing device such as a laptop computer, a tablet computer, a mobile phone and the like. The computing device  300  may include a bus or other communication mechanism for communicating information among various components of the computing device  300 . In its most basic configuration, computing device  300  typically includes at least one processing unit  306  and system memory  304 . Depending on the exact configuration and type of computing device, system memory  304  may be volatile (such as random access memory (RAM)), non-volatile (such as read-only memory (ROM), flash memory, etc.), or some combination of the two. This most basic configuration is illustrated in  FIG.  3    by dashed line  302 . The processing unit  306  may be a standard programmable processor that performs arithmetic and logic operations necessary for operation of the computing device  300 . 
     Computing device  300  may have additional features/functionality. For example, computing device  300  may include additional storage such as removable storage  308  and non-removable storage  310  including, but not limited to, magnetic or optical disks or tapes. Computing device  300  may also contain network connection(s)  316  that allow the device to communicate with other devices. Computing device  300  may also have input device(s)  314  such as a keyboard, mouse, touch screen, etc. Output device(s)  312  such as a display, speakers, printer, etc. may also be included. The additional devices may be connected to the bus in order to facilitate communication of data among the components of the computing device  300 . All these devices are well known in the art and need not be discussed at length here. 
     The processing unit  306  may be configured to execute program code encoded in tangible, computer-readable media. Computer-readable media refers to any media that is capable of providing data that causes the computing device  300  (i.e., a machine) to operate in a particular fashion. Various computer-readable media may be utilized to provide instructions to the processing unit  306  for execution. Common forms of computer-readable media include, for example, magnetic media, optical media, physical media, memory chips or cartridges, or any other non-transitory medium from which a computer can read. Example computer-readable media may include, but is not limited to, volatile media, non-volatile media and transmission media. Volatile and non-volatile media may be implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data and common forms are discussed in detail below. Transmission media may include coaxial cables, copper wires and/or fiber optic cables, as well as acoustic or light waves, such as those generated during radio-wave and infra-red data communication. Example tangible, computer-readable recording media include, but are not limited to, an integrated circuit (e.g., field-programmable gate array or application-specific IC), a hard disk, an optical disk, a magneto-optical disk, a floppy disk, a magnetic tape, a holographic storage medium, a solid-state device, RAM, ROM, electrically erasable program read-only memory (EEPROM), flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices. 
     In an example implementation, the processing unit  306  may execute program code stored in the system memory  304 . For example, the bus may carry data to the system memory  304 , from which the processing unit  306  receives and executes instructions. The data received by the system memory  304  may optionally be stored on the removable storage  308  or the non-removable storage  310  before or after execution by the processing unit  306 . 
     Computing device  300  typically includes a variety of computer-readable media. Computer-readable media can be any available media that can be accessed by device  300  and includes both volatile and non-volatile media, removable and non-removable media. Computer storage media include volatile and non-volatile, and removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. System memory  304 , removable storage  308 , and non-removable storage  310  are all examples of computer storage media. Computer storage media include, but are not limited to, RAM, ROM, electrically erasable program read-only memory (EEPROM), flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by computing device  300 . Any such computer storage media may be part of computing device  300 . 
     It should be understood that the various techniques described herein may be implemented in connection with hardware or software or, where appropriate, with a combination thereof. Thus, the methods and apparatuses of the presently disclosed subject matter, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other machine-readable storage medium wherein, when the program code is loaded into and executed by a machine, such as a computing device, the machine becomes an apparatus for practicing the presently disclosed subject matter. In the case of program code execution on programmable computers, the computing device generally includes a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. One or more programs may implement or utilize the processes described in connection with the presently disclosed subject matter, e.g., through the use of an application programming interface (API), reusable controls, or the like. Such programs may be implemented in a high level procedural or object-oriented programming language to communicate with a computer system. However, the program(s) can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language and it may be combined with hardware implementations. 
     The techniques for making a determination about an eye in ambient lighting conditions described herein can optionally be implemented with a mobile computing device, such as a laptop computer, tablet computer or mobile phone. Accordingly, the mobile computing device is extremely small compared to conventional devices and is very portable, which allows the mobile computing device to be used wherever needed. Many conventional devices have a chin rest that requires the subjects to only look straight ahead during this testing. Unlike conventional devices, the mobile computing device can be placed in any position relative to the subject&#39;s head where the eyes can still be viewed and measurements can be made. 
     It should be appreciated that the logical operations described herein with respect to the various figures may be implemented (1) as a sequence of computer implemented acts or program modules (i.e., software) running on a computing device, (2) as interconnected machine logic circuits or circuit modules (i.e., hardware) within the computing device and/or (3) a combination of software and hardware of the computing device. Thus, the logical operations discussed herein are not limited to any specific combination of hardware and software. The implementation is a matter of choice dependent on the performance and other requirements of the computing device. Accordingly, the logical operations described herein are referred to variously as operations, structural devices, acts, or modules. These operations, structural devices, acts and modules may be implemented in software, in firmware, in special purpose digital logic, and any combination thereof. It should also be appreciated that more or fewer operations may be performed than shown in the figures and described herein. These operations may also be performed in a different order than those described herein. 
       FIG.  4    illustrates an example method for making a determination about an eye of a subject based upon ambient light reflected out of the eye. The method comprises step  402 , detecting, using a computing device, ambient light reflected out of an eye of a subject from a retina of the eye of the subject; and step  404 , making a determination about the eye of the subject based upon the reflected ambient light. 
     Making the determination about the eye of the subject based upon the reflected ambient light comprises making a determination based at least in part on an aspect of the reflected ambient light. The aspects can include making a determination based at least in part on an overall brightness (luminescence) of an image of the eye and the intensity of one or more colors of the reflected ambient light. Consider one non-limiting example where the determination about the eye of the subject comprises refractive error and the refractive error is determined by a formula developed through regression analysis. The example formula considers overall brightness (“LuminancePupil”) of the pupil from the image capture using only ambient light and the intensity of blue from one or more pixels from the pupil in the image (“BluePixel”), the intensity of red in one or more pixels from the pupil in the image (“RedPixel”), and the intensity of green in one or more pixels from the pupil in the image (“GreenPixel”) while controlling for ambient light levels (“LuminanceAmbient”). The example formula comprises: Refractive Error=−36.47+(−638.37*RedPixel)+(−1807.2*GreenPixel)+(−333.64*BluePixel)+(2156.5*LuminancePupil)+(183.0*LuminanceAmbient)m+(890.2*GreenPixel*LuminanceAmbient)+(−4895.0*RedPixel*RedPixel)+(−8457.1*GreenPixel*GreenPixel)+(−1711.4*BluePixel*BluePixel)+(1592.8*LuminancePupil*LuminancePupil)+(−178.7*LuminanceAmbient*LuminanceAmbient), and has an R 2  of approximately 0.78 for fitting the measurement to the intended refractive error of the eye. It is to be appreciated that this is only one example of a formula for making a determination about the eye and other formulas are contemplated within the scope of this disclosure. 
     Referring back to the method described in  FIG.  4   , detecting ambient light reflected out of an eye of a subject from a retina of the eye of the subject can further comprise capturing, using an image capture device, an image of the eye of a subject, wherein the image is captured using only ambient lighting conditions and wherein non-relevant reflections from the eye of the subject are managed while capturing the image; determining, using the computing device, an overall intensity of light from a plurality of pixels located within at least a portion of a pupil captured in the image; determining, using the computing device, a first intensity of a first color from the plurality of pixels located within at least a portion of a pupil of the eye of the subject captured in the image; determining, using the computing device, a second intensity of a second color from the plurality of pixels located within the at least a portion of the pupil of the eye of the subject captured in the image; and comparing, by the computing device, a relative intensity of the first color and a relative intensity of the second color, wherein the comparison and the overall intensity are used to make the determination about the eye of the subject based upon the reflected ambient light. For example, when the intensity of the first color is brighter relative to the intensity of the second color and an overall intensity is relatively brighter, the determination about the eye of the subject based upon the reflected ambient light comprises a positive value or hyperopia. Conversely, when the intensity of the first color is dimmer relative to the intensity of the second color and an overall pixel intensity is relatively dimmer, the determination about the eye of the subject based upon the reflected ambient light comprises a negative value or myopia. The first color can comprise any one or any combination of red green and blue and the second color can comprise any one or any combination of red, green and blue. 
     In the method of  FIG.  4   , the determination about the eye of the subject based upon the reflected ambient light can alternatively or optionally comprise an autorefraction or a photorefraction measurement. Capturing, using the image capture device, an image of the eye of the subject can comprise capturing a first image using only ambient lighting conditions with the image capture device through a spectacle lens or a contact lens while the subject is wearing the spectacle lens or the contact lens over the eye and capturing a second image using only ambient lighting conditions with the image capture device while the subject is not wearing the spectacle lens or the contact lens over the eye and the aspects of the reflected ambient light in the first image can be compared to the aspects of the reflected ambient light in the second image and the determination about the eye of the subject based upon the reflected ambient light is based on the comparison and comprises an estimated prescription for the spectacle lens or the contact lens. 
     The method shown in  FIG.  4    can further comprise making a first determination about the eye of the subject based upon the reflected ambient light from a first plurality of pixels located within the portion of the pupil of the eye of the subject captured in the image; making a second determination from a second plurality of pixels located within the portion of the pupil of the eye of the subject captured in the image, wherein the second plurality of pixels are a subset of the first plurality of pixels; making a third determination from a third plurality of pixels located within the portion of the pupil of the eye of the subject captured in the image, wherein the third plurality of pixels are a subset of the first plurality of pixels and are separate from the second plurality of pixels; and comparing the first determination, the second determination and the third determination to make the determination about the eye of the subject based upon the reflected ambient light. Comparing the first determination, the second determination and the third determination to make the determination about the eye of the subject based upon the reflected ambient light can comprise one or more of determining a standard deviation of the first determination to the second determination, a standard deviation of the first determination to the second determination, or a standard deviation of the second determination to the third determination, wherein the determined standard deviation indicates the determination about the eye of the subject based upon the reflected ambient light. For example, the determination about the eye of the subject based upon the reflected ambient light can be the presence or the absence of astigmatism. When the presence of astigmatism is detected, an amount of astigmatism can be determined by comparing the overall intensity and the relative intensity of the first color or the relative intensity of the second color of various regions of the pupil. Such measurements of various regions of the pupil can comprise measuring one or more of hyperopia or myopia at the various regions of the pupil. 
     As noted above, the method of  FIG.  4    can include managing non-relevant reflections from the eye while capturing the image, which can comprise managing reflections from a cornea or a lens of the eye of the subject while capturing the image. For example, a polarizing filter can be placed over a lens of the image capture device or between the image capture device and the eye of the subject. Managing non-relevant reflections from the eye while capturing the image can also comprise blocking light that would lead to reflections from a corneal surface of the eye or a lens of the eye. For example, a surface can be provided that absorbs light or prevents the non-relevant reflections from the eye while capturing the image. In one aspect, the surface can have a black matte finish. In various aspects the surface can comprise a portion of the image capture device or at least a portion of a case that houses the image capture device. 
       FIG.  5    illustrates an alternate example method for making a determination about an eye of a subject based upon ambient light reflected out of the eye. The method comprises step  502 , capturing, using an image capture device, an image of an eye of a subject, wherein said image is captured using only ambient lighting conditions and wherein non-relevant reflections from a cornea and a lens of the eye of the subject are managed while capturing the image. At step  504 , an average red intensity can be determined from a plurality of pixels located within at least a portion of a pupil captured in the image. At step  506 , an average blue intensity is determined from the plurality of pixels located within the at least a portion of a pupil captured in the image. At step  508 , an overall intensity is determined of the plurality pixels located within the at least a portion of a pupil captured in the image; and, at step  510 , compare the average red intensity and the average blue intensity, wherein the comparison and the determined overall intensity are used to determine an optical quality of the eye. 
     In the method of  FIG.  5   , the determination about the eye of the subject based upon the reflected ambient light can alternatively or optionally comprise an autorefraction or a photorefraction measurement. Capturing, using the image capture device, an image of the eye of the subject can comprise capturing a first image using only ambient lighting conditions with the image capture device through a spectacle lens or a contact lens while the subject is wearing the spectacle lens or the contact lens over the eye and capturing a second image using only ambient lighting conditions with the image capture device while the subject is not wearing the spectacle lens or the contact lens over the eye and the aspects of the reflected ambient light in the first image can be compared to the aspects of the reflected ambient light in the second image and the determination about the eye of the subject based upon the reflected ambient is based on the comparison and comprises an estimated prescription for the spectacle lens or the contact lens. 
     The method shown in  FIG.  5    can further comprise determining a presence or an absence of astigmatism. If the presence of astigmatism is indicated, an amount of astigmatism can be determined by comparing optical quality measurements of various regions of the pupil. Such optical quality measurements of various regions of the pupil can comprise measuring one or more of hyperopia or myopia at the various regions of the pupil. 
     As noted above, the method of  FIG.  5    can include managing non-relevant reflections from the eye while capturing the image, which can comprise managing reflections from a cornea or a lens of the eye of the subject while capturing the image. For example, a polarizing filter can be placed over a lens of the image capture device or between the image capture device and the eye of the subject. Managing non-relevant reflections from the eye while capturing the image can also comprise blocking light that would lead to reflections from a corneal surface of the eye or a lens of the eye. For example, a surface can be provided that absorbs light or prevents the non-relevant reflections from the eye while capturing the image. In one aspect, the surface can have a black matte finish. In various aspects the surface can comprise a portion of the image capture device or at least a portion of a case that houses the image capture device. 
     As used herein, at least one of the subject&#39;s eyes can be the subject&#39;s left eye or right eye. Alternatively, at least one of the subject&#39;s eyes can be the subject&#39;s left eye and right eye. This disclosure contemplates that the optical qualities based on the subject&#39;s left eye and right eye can be the same or different. 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.