Abstract
Amblyopia is a neurodevelopmental disorder defined as a reduction in visual acuity that cannot be corrected by optical means. It has been associated primarily with other low level visual deficits such as reduced contrast sensitivity at high spatial frequencies and increased visual crowding. Research in the last decade demonstrated that amblyopia is also linked to higher-level deficits in global shape and motion perception and in contour integration. Deficits in visual attention have also been shown in counting briefly presented items, tracking objects and identifying items presented in rapid succession. Here, we demonstrated that amblyopia causes more general attentional deficits as manifested in visual search. We compared the performance of subjects with amblyopia (n=9) to those of controls (n=12) on a feature search and a conjunction search with Gabor patches. Eye movements were recorded and controlled by continuous fixation. To account for the low level deficits inherent in amblyopia, we first measured each subjects’ contrast and crowding thresholds and then presented the display elements at suprathreshold levels such that visibility was equalized across the control and the experimental groups. The effectiveness of these precautions at eliminating low-level deficits as a confounding factor was confirmed by the results of the feature search task. Performance on this “pop-out” search, considered to be pre-attentive, was not significantly different between the two groups. In contrast, reaction times on conjunction search, a task requiring the engagement of visual attention, were significantly greater (by as much as 400 msec) in amblyopic eyes than in control or fellow eyes. Taken together, these data suggest that amblyopia is linked to greater and more generalized attentional deficits than previously known. Visual search is a necessary, basic component of everyday functioning and these deficits may result in significant repercussions for people with amblyopia.
Meeting abstract presented at VSS 2015