A directional impairment of eye movement control in strabismus amblyopia

Saccadic and pursuit tracking movements were elicited to determine the ability of the amblyopic eye to sense and respond to position and motion of the retinal image. Amblyopic eyes were found to initiate saccades as rapidly as normal eyes (200 to 300 msec.), however, the amblyopic eye's saccades were reduced in amplitude, highly variable, and required refinement by subsequent saccades, particularly in response to nasalward displacements of the retinal image. Pursuit responses of amblyopic eyes to both constant and sinusoidal velocity targets contained brief periods of abnormally slow following movements interrupted by position-corrective saccades. As with the saccadic response, the amblyopic eye's pursuit movements were more accurate for temporal than for nasal retinal image motion. Abnormal saccadic and pursuit eye movements in amblyopia result from reduced monocular position and velocity sensitivity probably associated with binocular suppression scotomas normally found in amblyopia.