Improving Binocular Vision Through Perceptual Learning

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Project Summary/Abstract Binocular vision endows us with superior perceptual abilities in numerous tasks including those involving fine depth detection (stereopsis), figure/ground segmentation, space perception and visually guided actions. Having good binocular vision benefits athletes in their sports (e.g., basketball and volleyball) and professionals whose vocations demand acute depth perception (e.g., surgeons, dentists, machinists, and pilots). A common cause of poor binocular vision is excessive sensory eye dominance, a condition that is found in some people with clinically normal vision and in people with lazy eye (amblyopia). Sensory eye dominance could be due to an interocular imbalance of inhibition or integration, or both. This translational proposal employs a novel push-pull perceptual learning protocol to reduce sensory eye dominance due to interocular imbalance of inhibition and to improve stereopsis in adults. This approach rests on the hypothesis that the perceptual learning effect on sensory eye dominance is more effective when it targets the putative inhibitory network to restore the balance of excitatory and inhibitory interactions between the two eyes. The push-pull protocol works by forcing the weak eye to perceive its stimulus (push) as it simultaneously suppresses the strong eye's stimulus from being perceived (pull). This protocol is contrasted with a push-only protocol that solely stimulates the weak eye (push) while the strong eye is not stimulated. The push-pull protocol, and not the push-only protocol, results in significantly reduced sensory eye dominance and improved stereopsis in non-amblyopes and amblyopes. This proposal has three specific aims. Aim 1 implements the push-pull protocol due to interocular imbalance of inhibition on a larger spectrum of amblyopic subjects (a heterogeneous group). The outcomes will provide a broader knowledge of how amblyopes respond to the perceptual learning protocol. Aim 2 implements the push-pull protocol on non-amblyopes and improves on the utility and potency of the push-pull protocol by capitalizing on, and exploring, the basic underlying mechanisms related to attention, contrast gain control, channel bandwidths, etc. Aim 3 investigates interocular imbalance of integration, identifies its underlying deficits using the multi-channel model of contrast gain control and incorporates the knowledge of interocular inhibition to develop a combined protocol to reduce sensory eye dominance. Reflecting the nature of this translational proposal, lessons learned from Aims 2 and 3 will be applied to Aim 1 and vice versa. The outcomes of this proposal, which focuses on restoring the interocular balance of excitatory and inhibitory interactions, will lead to improved binocular vision in people with normal vision who desire finer depth perception ability and in people with amblyopia. The long-term goal is to apply the knowledge gained into clinical application for the treatment of binocular visual disorders, including amblyopia. The latter affects 2-3% of the population and if left untreated could lead to adverse personal and societal consequences.