Disturbance of the oculomotor system due to lateral fixation

Three experiments are reported on the effects of previous lateral deviation of the eyes. There is a large effect on their subsequent resting position, and a smaller instantaneous effect on voluntary eye centring. Both are in the direction of previous fixation. The latter effect becomes insignificant within 30 s. The treatment produces errors in visually guided reaching away from the previous direction of fixation. The effects are consistent with a change in registered eye position, an effect also produced by exposure to prisms. Despite this similarity, the disturbance to the oculomotor system caused by these two treatments is sharply differentiated by the resting position. Prisms cause subsequent low frequency, high amplitude oscillations of the eyes (Craske and Templeton, 1968), whereas following lateral deviation the mean resting position returns gradually towards the pre-treatment position.