Development and Validation of a Holographic Waveguide-based Oculometer for Objective and Comprehensive Oculomotor Disorder Assessment

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Summary: The goal of this research is to test the feasibility of applying the existing Holographic Waveguide (HW) technology to conduct comprehensive and objective clinical evaluation of binocular eye movement, accommodation and pupil size (oculomotor components). In humans, these components are intricately coupled to form coherent visual routines for viewing targets at different directions and distances (the triad). Abnormalities in oculomotor components and in their interactions are a highly prevalent health issue, often associated with visual symptoms and difficulties completing educational and work-related tasks. Current clinical oculomotor assessments typically evaluate individual oculomotor components in isolation and usually rely on the patient's subjective report and on clinician's subjective judgment. The difficulties caused by the lack of devices that can perform objective, simultaneous assessment of all oculomotor responses have long been recognized by clinicians and researchers alike. HW technology may serve as the platform for such a device. In a HW, light signal is coupled into a glass substrate at an angle satisfying the requirement of total internal reflection via a thin-film holographic in-coupler pasted at one location on the substrate, propagates in the substrate and is coupled out from the substrate at a different location via a matching out-coupler. It provides a highly compact and lightweight light signal pipeline--a piece of glass in front of the eye--that can conduct illumination light to the eye and also capture light reflected back from the eye. The purpose of the proposed research is to test the feasibility of using a HW-based oculometer to perform objective measurement all oculomotor components. To achieve this goal, two specific aims will be pursued. First, a desktop prototype of a HW-based oculometer will be developed. Near infrared light will be waveguided to a location in front of the eye to provide co-axial illumination. Reflections from the cornea, the pupil and the retina will be captured in front of the eye and will be waveguided to a camera and a wave-front sensor to extract eye movement and accommodation data. Second, the accuracy and precision of the prototype will be evaluated first with model eyes and then with young normal human subjects. The human subject evaluations will include fixation, saccade, vergence and accommodation recordings with the prototype. These recordings will be compared with recordings obtained with commercially available eye tracker and autorefractor. It is our goal to reach a 0.1o or better precision over a range of 15o of visual angles for eye movement and a 0.35 diopters or better precision over a range of 12 diopters for accommodation. If HW is proven a viable platform for oculomotor assessment, a HW-based, wearable, see-through clinical device will be developed that can assess all oculomotor responses objectively and simultaneously over longer period of time while the patient is engaged in normal visual activities, such as reading and writing at a desk. Not only will it improve the quality and efficiency of current oculomotor disorder care but will also improve diagnosis of intermittent, task-related, or emergent disorders.