Deficient maximum motion displacement in amblyopia

Abstract

Direction discrimination thresholds for maximum motion displacement ( D max) are not fixed, but are stimulus dependent. D max increases with reduced dot probability or increased dot size. We previously reported abnormal D max in the fellow eyes of amblyopic children for dense patterns of small dots. To determine how deficits of D max in amblyopic eyes compare to those in fellow eyes, thresholds were obtained in both eyes of 9 children with unilateral amblyopia and 9 control children. The expected increase in D max was observed for reduced dot probability and increased dot size conditions relative to baseline in both control and amblyopic groups. Both eyes of the amblyopic group demonstrated significant deficits. Our findings implicate abnormal binocular motion processing, which may involve both low-level and high-level motion mechanisms, in the neural deficit underlying amblyopia.