Insight into neural mechanisms of strabismus from studies in non-human primate models

Binocular alignment and binocular coordination of eye movements are important in foveate species. Developmental loss of sensory or motor fusion leads to ocular misalignment (strabismus) in as much as 5% of all children making this disease a significant public health issue. The overall goal of research in our laboratory is to understand oculomotor mechanisms underlying disruption in binocular alignment and binocular coordination of eye movements in strabismus. Our strategy is to utilize a basic science approach with behavioral studies of eye alignment and eye movements, and neurophysiological studies of oculomotor circuits in awake-behaving strabismic monkeys. In the first part of this seminar presentation, I will present evidence suggesting that a circuit that serves slow vergence eye movements in the normal animal is involved in setting the state of eye misalignment in strabismus. Another avenue of research in our lab is to investigate strabismus treatments methods in animals with strabismus. Strabismus surgery is well documented in both the literature and in practice with varying levels of success and permanence. Potentially, muscle remodeling and/or central neural adaptation affects the final state of misalignment after treatment. In the latter part of the seminar presentation, I will present results from some ongoing studies in our lab recording from neurons in the oculomotor and abducens nuclei before and after surgical treatment of strabismus in non-human primates with strabismus. Our data suggests that a neural adaptive response begins soon after surgery and over the longer term, continued neural adaptation in addition to muscle remodeling is responsible for setting the steady-state strabismus angle after treatment.