Abstract
Purpose: :
Subjects with strabismus have shown deficits in disparity vergence eye movements. We investigated how their damaged vergence system responded to optic flow motion in the ground plane.
Methods: :
Backward/forward motion of a sinusoidal grating pattern which does not have horizontal disparity was displayed on a computer monitor in the ground plane and binocular movements were recorded with a video-based eye tracking system (EyeLink 1000 desktop). Subjects looked at the center of the pattern for 5 seconds in each trial and various velocities and two different directions were randomized. Open-loop and closed-loop vergence velocities, amplitudes, and latencies were quantified and compared with normal subjects.
Results: :
In normal subjects, involuntary horizontal vergence nystagmus was recorded. In patients, robust vergence nystagmus was also induced. The slow-phase velocity of open-loop vergence from strabimus subjects was higher than normal subjects and the latency of the initail responses was shorter than normal subjects. The closed-loop vergence from strabismus patients was as strong as normal subjects.
Keywords: vergence • strabismus • eye movements