Optimal magnification and oculomotor strategies in low vision patients

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PROJECT ABSTRACT Low vision patients with bilateral central scotomas usually develop a preferred retinal locus (PRL) close to the border of the scotoma that tries to substitute for the lost foveae. However, functionally the PRL falls short of the challenge and such patients have poor visual acuity and contrast sensitivity, poor oculomotor control, and frequently lose objects of interest in the nearby perceptually filled-in binocular scotoma. We are proposing a new approach to low vision enhancement and low vision rehabilitation for these patients using real-time digital processing and remapping of large field of view images presented binocularly in a head-mounted display equipped with video scene cameras and eye and head trackers. Specifically, we propose testing the benefits and side-effects of an innovative vision enhancement strategy called the HMD-bubble, which is a localized region of magnification and contrast enhancement in a video image from a camera mounted on a head mounted display (HMD). There are two types of HMD-bubbles we have implemented: the "fixed" HMD-bubble where the region of magnification is "fixed" relative to display coordinates, and the "eye tracking" HMD-bubble where the region of magnification follows patients' eye movements. The size, shape, and level of magnification of both HMD-bubbles can be dynamically adjusted by the patient, allowing customization of the HMD-bubbles. The fixed HMD-bubble is relatively easy for patients to usel. The eye tracking HMD-bubble however is generally much harder for patients to control when they first use it, necessitating the development of exercises and training programs. Since eye movements are faster than head movements, the eye tracking HMD-bubble should be superior to the fixed bubble, if patients can learn to control it. We will also investigate the potential benefits of providing stereo binocular information in and/or around a HMD-bubble, as that step is arguably the most important remaining development at this time with HMD vision enhancement systems.. Aim 1 is to measure the performance of low vision patients with bilateral central scotomas in tasks relevant to their daily lives when using a fixed or eye tracking HMD-bubble. The performance measures include reading, facial expression recognition and identification, eye-hand coordination, and speed and accuracy of performing selected daily living tasks. We also will periodically measure discomfort severity associated with “simulator sickness”. Aim 2 is to develop and evaluate exercises and training programs designed to help patients adjust to and optimize the use of a HMD-bubble. Aim 3 is to determine if stereo binocular information in and/or around HMD-bubbles is of potential benefit to patients. We will use monocular and binocular contrast sensitivity measures to determine if binocular inhibition or suppression is occurring and measure the location of corresponding retinal points to determine if the patient can attain single binocular vision and to what extent the magnification bubble distorts the horopter. Finally, we will explore patients’ capabilities of controlling the binocular eye tracking bubble while making vergence eye movements.