Abstract
Amblyopia is a developmental disorder of spatial vision. In addition to basic low-level visual deficits, there is evidence suggesting that amblyopes also have some cognitive deficits, namely in perceptual decision-making and visual search, both of which rely on gathering sufficient evidence to process a visual stimulus. A prior study found that latencies were significantly longer in complex visual search tasks in the amblyopes with either eye viewing, when compared to visually-typical participants. The goal of the current study was to examine the effects of amblyopia on the dynamics of visual search to understand what aspects of visual processing are affected. We used a speed-accuracy trade-off (SAT) procedure to examine these dynamics. We tested both visually-typical and amblyopic adults monocularly on a 4 x 4 visual search display, presented for various durations ranging from 40ms to 2000ms. In the search array, one letter “L” was the target and many letters “T” were distractors. The target letter could appear in any location within the array and the remaining locations were populated with heterogeneously oriented T’s. The participants were tasked to find the target “L” and report its direction (left- or right-facing) within a 365ms response window. Eye movements were tracked and recorded. We found that amblyopes’ latencies were significantly slower for the non-dominant eye than for the fellow eye, which was similar to each eye of visual-typical participants. Amblyopes also showed impaired accuracy with the amblyopic eye viewing. Their SAT function’s asymptote (corresponding to discriminability) and the pre-asymptotic rise (corresponding to the rate of information accrual) were both lower for the amblyopic eye only. This result shows that amblyopia is not only marked by impaired discriminability and longer response latency, but it is also characterized by a slower rate of information accrual during amblyopic eye viewing.