Metacontrast masking in amblyopia.

Measured the time course of visual signals arising from each eye of 4 strabismic and/or anisometropic amblyopes and 2 visually normal Ss using monoptic metacontrast masking. The amblyope Ss had 1 nonamblyopic eye, clear ocular media, and normal fundi. The method involved the brightness estimation of a high-contrast disk target whose visibility varied as a function of the stimulus onset asynchrony (SOA) of a subsequent annular mask. Results indicate that the SOA of optimal masking was delayed in the amblyopic eye compared to that of the fellow nonamblyopic eye or with normal eyes. The smaller the target, the greater was this SOA difference and the broader was the amblyopic U-shaped masking function. This finding is discussed in terms of the current model of metacontrast and represents the differential effect of the amblyopic process on human sustained and transient neurons. (French abstract) (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)