The pattern of changes produced in the saccadic system and vestibuloocular reflex by visually patching one eye

Abstract

The purpose of the present study was to determine whether, in the absence of visual input to one eye, saccades remained equal in the two eyes. The same question was addressed for the VOR gain of the two eyes. After 1 wk during which one eye was continuously patched, the saccadic properties of only the unseeing eye showed changes consisting of a change, usually a decrease, in saccadic step magnitude, postsaccadic drift with an exponentially decaying component in the temporal direction, and the appearance of a vertical component as well as vertical postsaccadic drift during horizontally directed saccades. Effects were also observed in the VOR consisting of a change in gain and a vertical component during horizontal head rotation. As with saccades, the vertical component in the patched eye was upward when the eye was deviated nasally. When the patch was removed, normal function was restored within 1 day to the previously patched eye without impairing the function of the unpatched eye. These results suggest that the conjugate nature of saccades and the VOR is in part the consequence of a selective, visually driven, calibration mechanism, which can alter commands to motoneurons of one muscle of a conjugate muscle pair without affecting commands to the other. The similarity of changes observed in the VOR and saccades after patching suggests that elements common to both are altered in the absence of vision.