Eye Exam in the Virtual World: a Pilot Study

: This study investigated the feasibility of using three - dimensional (3D) technology as a multi - functional visual stimulus to assist the clinical eye exam. Specifically, we examined: (1) whether the receding movement of a 3D fixation target into distance could relax the accommodation of non - cycloplegic hyperopic subjects so that accurate refraction measurements could be achieved; (2) the feasibility of using the left - eye and right - eye images from the 3D monitor as the light source to perform swinging - flashlight pupil tests; and (3) the implementation of 3D technology to interrupt the binocular visual/motor fusion as required for the clinical cover test to identify strabismus. Using a 3D TV to provide visual stimuli and a photoscreening (PS) device, near - infrared (NIR) eye images were acquired and analyzed for each of the three objectives. The result of accommodation test showed that with visual stimuli, the maximal hyperopic refractions could more accurately suggest the patients ’ true refractions and the more hyperopic patients responded more to the 3D projected distance. However the very mild hyperopia did not show significant response. The pilot tests also showed distinguishable normal and abnormal pupillary responses with 3D image illumination and also the difference in phoria and tropia in the ocular alignment test using 3D stimuli.


Introduction:
In recent years virtual reality (VR), augmented reality (AR), and various types of 3D-imaging technology have blossomed. Stereoscopic technology provides more realistic perception to viewers. In medical practices, it allows more accurate analyses of the morphology, and therefore, helps to improve surgical accuracy, reduce operation times, and enhance patient safety [1,2]. 3D technology can also be applied in an altered way, for the vision assessment. Stereoscopic viewing requires both eyes to work in coordination as they converge, focus, and track the target. Deficiencies of such coordination reveal difference between two eyes and undiagnosed problems [3]. As indicated in the "3D in the classroom" document from American Optometry Association, "the ability to perceive depth in a 3D presentation is an effective vision health indicator that has much higher sensitivity than the standard eye chart that has been used for the last 150 years" [4].
Children with ocular diseases are often unaware of their impairment until a later stage when treatment is less effective. The importance of regular vision screening is indisputable, but comprehensive examinations for all children would put a significant strain on limited clinical health-care resources. The growing popularity with children in VR and 3D-video games has provided a potentially effective treatment for amblyopia [5][6][7] and a promising intervention of children's myopic development [8] and may be an approach for assisting and lessen the burden of pediatric vision assessment. Currently, a large number of clinical ocular exams rely on the clinician's observation while visual stimuli are applied with tools that include a penlight, an eye patch or a visual occluder, an optotype, and fixation targets at different distances. While 3D technologies, especially when presented as animation, are attractive to children, they could simultaneously function as a versatile clinical tool that provides independent optical stimuli to each of the Also examined was the application of 3D technology to interrupt the binocular visual/motor fusion as the cover test requires.

Experiment and Method
The human subjects of this pilot study were 155 volunteers with an age range of 4 to 81 years old who were recruited in their visit at Walmart vision center [9].
We used a binocular infrared photoscreening (PS) device, the Dynamic Ocular Evaluation System (DOES) [9,10] All subjects received comprehensive eye exams in the same visiting period.

Accommodation Test
The first of the three tests in this study is to check the feasibility of relaxing visual accommodation by 3D stimuli. Although the ocular accommodation driven by 3D displays were discussed in many studies [11][12][13][14][15][16][17][18], the relaxing of accommodation in hyperopic objects has never been studied. Because that measuring hyperopia in children is often masked by accommodation, and hyperopia is a significant risk factor of developing amblyopia, it is important to relax children's accommodation for accurate assessment. In optometric practices, the fogging technique, which places a positive lens in front of an eye while the eye views a distant target, is often used for relaxation purpose. However, the effectiveness of this technique is often insufficient.
Since ocular accommodation can be driven by many different types of monocular and binocular visual cues, Horwood and Riddell investigated and compared the effectiveness of several of them and they concluded that the most effective stimuli to relax accommodation was the binocular targets receding into the distance [19].
The test here is to examine whether the 3D target that recedes into the distance could also relax accommodation effectively like the real physical objects used by Horwood and coworkers.
In the clinical testing cohort, we included only hyperopic subjects younger than 35 years of age who had healthy accommodation. Both eyes of the subjects must be hyperopic, their cylinder-refractive error must be less than 1.5 diopters, and the best corrected visual

Pupil Test
The second test simulates the clinical swinging-

Cover Test
Strabismus is one of the important screening targets that link to amblyopia development. The Hirschberg method is a simple and objective test to identify the binocular mis-alignment. It measures the locations of corneal light reflections. Any asymmetry between the two eyes or significant deviation from the pupil centers indicates a potential ocular mis-alignment.
Although this method is easy to implement, the diagnostics is not as reliable when compared to the subjective cover-uncover test, which actively disturbs the binocular vision to stimulate and reveal the abnormality [20,21]. Cover test is usually considered the clinical standard, but it requires a more skilled clinician to perform the test. In this demonstration, we use 3D technology's separated right-eye and left-eye input feature to eliminate the visual fixation target from the background to one eye to achieve the similar effect of using a visual occluder in the clinical cover test. The disappearance of the viewing object in one eye will prompt the viewer to use the other eye to look at the target which is similar to the "cover" portion of the cover -uncover test. The reappearance of the absent fixation target in the 3D image is similar to the "uncover"   its distance did not appear to be affective to their accommodation. They appeared to accommodate with small magnitude constantly.     Phoria is a deviation that occurs when fusional stimuli are absent. For binocular viewing, both eyes'

Pupil Test Result
foveas are aligned to the fixation target. When one eye is suddenly covered, the (relative) alignment is assumed appropriately by the covered eye. However, the eye will gradually relax and drift away from the initial projection.
When a covered-eye was uncovered, this eye would quickly re-align (its fovea) to the visual stimulus to form motor fusion and reclaim binocular vision. Therefore, the uncover shifting is more noticeable than the cover drifting. Figure 8 shows  For a tropia, the binocular viewing motor fusion is not present. When a viewing target is presented to a tropia, only one eye is aligned to the target whether it is a right-eye, left-eye, or alternating between the two eyes. Figure 9 shows a case of a left esotropia (LET). There are many advantages in the 3D visual stimuli eye assessment. In additional to having a playful and close-to-natural viewing and testing atmosphere, the use of NIR video prevent the difficulty of observing patients directly in typically dimmed clinic room illumination. Digital results from such applications can be easily stored and evaluated by clinicians at convenient times in high resolution and slow motion if desired, which could reduce stress for both patient and clinician.
Digital recording helps to improve quantitative assessment and therefore, diagnostic accuracy.
Furthermore, digital data make automatic Computer Aided Diagnosis (CAD) possible to develop and allows establishing database and promoting advance in the Big Data era.