The relation of monocular optokinetic nystagmus to peripheral binocular interactions.

Human observers with deficient foveal stereopsis often show characteristic abnormalities of monocular optokinetic nystagmus (OKN). The present study examined the effect of binocular interactions in the peripheral visual field on these OKN deficits. A variety of binocular functions (binocular acuity summation, interocular suppression, motion-in-depth) were assessed at various positions throughout the visual field in subjects with deficient or no foveal stereopsis and related to monocular OKN deficits seen with different stimulus field sizes. Extent and location of peripheral binocular interactions accurately predicted the changes in monocular OKN observed with different field sizes. This indicates that the effects of early developmental conditions on cortical and subcortical binocularity, responsible for the deficits of stereopsis and OKN, show very close functional parallels. The results further suggested that monocular OKN deficits and peripheral acuity profiles are determined before the age of 5 yr.