How disturbed visual processing early in life leads to disorders of gaze-holding and smooth pursuit.

When synergistic interactions between visual and oculomotor systems are impaired early in life, strabismus, gaze instability, smooth pursuit asymmetry, and loss of visual function are likely to occur. These disorders are relatively common, permanent, and difficult to treat. We have developed effective animal models for infantile strabismus by raising infant monkeys (Macaca mulatta) with restricted binocular visual experience. We have found that the specific oculomotor disorders that occur with early onset strabismus depend on the type of early visual experience. Our approach allows us to examine the neural substrate associated with different components of infantile strabismus including latent nystagmus (LN) and smooth pursuit asymmetry. For example, we have found LN is most associated with loss of binocular visual sensitivity normally present in neurons of pretectal nucleus of the optic tract (NOT). In contrast, nasalward bias in smooth pursuit of strabismic monkeys could be associated with loss of binocular visual and eye movement sensitivity of neurons in medial superior temporal (MST) area.