The effect of bilateral visual cortex lesions on the development of eye movements and perception

We studied the eye movements and visual perception in a man with extensive bilateral occipital lesions acquired at birth. He had 3/500 acuity, limited visual fields, and extrafoveal fixation attributable to an intact left superior visual cortex. Analysis of digitized electro-oculography and magnetic search coil data showed normal saccade dynamics. He could make voluntary saccades. Smooth pursuit of suprathreshold targets was mostly saccadic and did not improve with added nonvisual cues. Our results support the hypothesis that the visual cortex is crucial to the development of eye movements. The foveal representation in the occipital lobes, missing in this subject, is needed for development of normal smooth pursuit.