Processing delays in amblyopic eyes: evidence from saccadic latencies

Saccadic latencies were measured in amblyopes with constant strabismus, amblyopes without strabismus, and intermittent strabismics with or without amblyopia. Subjects tracked a small spot of light, either monocularly or binocularly, which moved with random horizontal step displacements of 0.25--8.5 deg over the central field. Increased saccadic latencies were observed in the amblyopic eyes of 6 of 11 subjects, with or without strabismus; saccadic latencies were similar in each eye of 2 subjects having intermittent strabismus without amblyopia. Amblyopia was a necessary condition for increased saccadic latencies and not strabismus. Evidence for normal motor control of eye movements in amblyopic subjects is as follows: normal saccadic durations in the amblyopic eyes, normal saccadic-latency distribution curves for binocular tracking and monocular tracking with the nonamblyopic eyes, and synchronous movements of the 2 eyes. Our results are interpreted in terms of a processing delay in the sensory pathways leading from the central region of the amblyopic eye to the centers involved in saccadic initiation.