PROJECT SUMMARY Binocular vision relies on a synergy between sensory and motor fusional mechanisms that jointly construct a single percept of the environment from the differing images formed on the two retinae. A stereoscopic sensory representation of the environment is required for accurate binocular eye movements, which in turn are required for stereoscopic sensory vision. A failure in either component of this system, especially during development, can lead to permanent binocular vision impairment. Sensory impairments can include amblyopia, diplopia and suppression, oculomotor impairments can include strabismus and vergence insufficiency, while socio-economic sequelae include lost education, sport and job opportunities and elevated adverse health risks. The current treatments for amblyopia (occlusion and penalization) are primarily monocular and do not promote binocular perception or eye movement coordination. Similarly, treatments for strabismus do not typically address binocular perception. These limitations are at least partly due to a lack of practical methodologies for the assessment of sensory-motor function and partly due to a lack of coordinated sensory-motor therapies. Recent data show that there is significant plasticity in both sensory systems and motor systems, even in adults. Many groups are now exploring methods to promote sensory plasticity with digitally modified images in dichoptic games and movies, but considerably less attention has been directed to motor plasticity or sensory and motor plasticity together. We hypothesize that additional therapeutic gains and a lower risk of adverse side effects may be achieved with a combined sensory-motor therapeutic approach that is monitored by effective sensory-motor endpoints. We argue i) that the pace of commercialization of virtual reality therapies for anisometropic amblyopia intensifies the need simultaneously to understand sensory and oculomotor deficits in strabismic amblyopia and ii) that the high levels of recidivism following surgical intervention may benefit from combined sensorimotor rehabilitation. In Aim 1, we develop and evaluate efficient methods to measure sensory and motor deficits in people with binocular vision impairment and to provide a quantitative framework for evidence-based assessment of sensory-motor therapy. In Aim 2, we measure the impact across the visual field of strabismus on the three-dimensional representation of virtual and natural environments to understand how the distribution of naturally occurring depth statistics across the visual field may impact the development of binocular sensory and motor deficits and moderate their response to treatment. In Aim 3, we develop and evaluate feedback-based methods that aim to facilitate and maintain ocular alignment and examine the potential benefit of simultaneous sensory and motor interventions for binocular visual function. In each Aim, we employ both laboratory stimuli, because of their high level of control, and natural and virtual 3D scenes, because of their rich structure and relevance to real-world deficits. The overall goal is to demonstrate the theoretical foundation for combined sensory and motor therapeutic approaches to binocular visual dysfunction.

PROJECT NARRATIVE Binocular vision impairments are generally associated with a number of functional deficits that can severely impact the quality of life of the patients in their everyday life, affecting simple yet fundamental everyday actions like walking, grasping an object or reading and also adversely impact socio-economic opportunities. The proposed study is basic science research into the mechanisms of sensory and motor binocular vision impairment and is relevant to Public Health for three primary reasons: 1) it aims to provide a proof of concept for translating eye tracking and 3D stereo technology into the clinical practice related to binocular visual dysfunction including oculomotor deficits (such as strabismus and vergence insufficiency) and perceptual deficits (such as amblyopia, diplopia, stereo blindness and suppression); 2) it seeks to develop effective quantitative methodologies for the measurement of binocular impairments, both with synthetic stimuli and in natural environments and to quantify the distribution of depth information across the visual field in healthy and impaired visual systems; and 3) it seeks to develop the evidence base for non-invasive rehabilitation for binocular eye alignment disorders, with the aim of preventing the development and progression of binocular visual dysfunction and, when intervention is required, to augment existing therapies with rehabilitation to assist in the maintenance of binocular oculomotor control.