The binocular contribution to monocular optokinetic nystagmus and after nystagmus asymmetries in humans.

Stereoblind subjects show marked monocular asymmetries in both OKN and OKAN, while normal subjects produce more balanced nystagmus. There is a negative relationship between the magnitude of the asymmetries and the magnitude of a binocular contribution to OKN production as measured with dichoptic, strobe illumination. A second experiment with normal subjects corroborated this relationship, revealing a small, but significant asymmetry in these subjects' OKAN. Further, there was no correlation between the monocular nystagmus asymmetries and stereoacuity. The results are explained in terms of subcortical binocular mechanisms.