EFFECT OF EXPOSURE DURATION ON SPATIAL UNCERTAINTY IN NORMAL AND AMBLYOPIC EYES

Previous studies have found that the spatial uncertainty of amblyopes is critically dependent on temporal factors. These studies claim that the spatial uncertainty is much greater at short exposure durations. W e have reassessed the effect of exposure duration on the spatial uncer tainty of normal and amblyopic eyes using a task in which we can compe nsate for the loss in contrast sensitivity which inevitably occurs as exposure duration is shortened. Our task involved a three-element alig nment task, where each of the elements were spatial Gabors at two diff erent separations. We ensured that our stimuli were always displayed a t a fixed ratio above contrast detection thresholds at each exposure d uration. Our results show that for normal subjects, for well separated equi-visible stimuli, there is only a weak effect of exposure duratio n. A similar dependence is found for the dominant and amblyopic eyes o f a group of strabismic amblyopes. Dominant eyes of strabismic amblyop es show increased spatial uncertainty compared with normal subjects. A mblyopic eyes of strabismic amblyopes show increased spatial uncertain ty compared with their dominant fellow eye which is invariant with exp osure duration. Some subjects show a larger positional deficit at shor t durations when the stimuli are almost abutting.