Effects of unilateral ocular motor nerve palsies on smooth pursuit eye movements in adult patients.

AIM: The aim of this study was to investigate the influence of single ocular muscle weakness on smooth pursuit eye movements. METHODS: Infrared video recordings of horizontal and vertical eye movements were obtained from 14 adult patients with either unilateral abducens nerve palsy or trochlear nerve palsy. During the recordings, subsequent series of horizontal, vertical and oblique ramp stimuli of 10 degrees/s constant target velocity and +/-10 degrees amplitude were presented under monocular viewing conditions. RESULTS: In both forms of ocular nerve palsies, similar changes of pursuit eye movements were observed in the pulling plane of the paretic muscles. The movements of the covered paretic eye showed the lowest amplitude and gain values as well as the lowest numbers of catch-up saccades. The highest amplitude and gain values were calculated from the movements of the covered sound eye. The highest numbers of saccades, however, were produced by the fixating paretic eye. CONCLUSIONS: We conclude that the fixating paretic eye compensates for the paresis by raising the pursuit gain and the number of catch-up saccades. In the covered paretic eye, however, monocular adaptation is connected with a symmetric low pursuit gain and a reduced number of saccades in the pulling plane of the paretic muscle.

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.