Smooth pursuit eye movements in patients with ocular motor nerve palsies: a preliminary report

The trajectories, velocity, and co-ordination of smooth pursuit eye movements were investigated in 30 patients with ocular motor nerve palsies (including palsies of cranial nerves III, IV and VI). The recordings of horizontal and vertical eye movements were obtained by video-oculography under monocular viewing conditions. During the recordings, horizontal, vertical, and oblique target movements of 10 degrees /s constant velocity were presented to the subjects in succession. In contrast to normal subjects, smooth pursuit eye movements in patients with ocular nerve palsies showed considerable differences in dependence on the fixating eye. The smooth pursuit gain of the paretic eye was reduced for eye movements in the pulling plane of the paretic muscle. When viewing with the paretic eye, the tracking of the target was achieved by a series of refixation saccades, which also occurred in the occluded normal eye. Consequently, the sound eye position overshot the target. The transition from a smooth to a saccadic pursuit pattern was accompanied by a spatial deviation of the eye movement trajectories from the path of the fixation target.