Visual search deficits in amblyopia

Abstract

Amblyopia is a neurodevelopmental disorder defined as a reduction in visual acuity that cannot be corrected by optical means. It has been associated with low-level deficits. However, research has demonstrated a link between amblyopia and visual attention deficits in counting, tracking, and identifying objects. Visual search is a useful tool for assessing visual attention but has not been well studied in amblyopia. Here, we assessed the extent of visual search deficits in amblyopia using feature and conjunction search tasks. We compared the performance of participants with amblyopia (n = 10) to those of controls (n = 12) on both feature and conjunction search tasks using Gabor patch stimuli, varying spatial bandwidth and orientation. To account for the low-level deficits inherent in amblyopia, we measured individual contrast and crowding thresholds and monitored eye movements. The display elements were then presented at suprathreshold levels to ensure that visibility was equalized across groups. There was no performance difference between groups on feature search, indicating that our experimental design controlled successfully for low-level amblyopia deficits. In contrast, during conjunction search, median reaction times and reaction time slopes were significantly larger in participants with amblyopia compared with controls. Amblyopia differentially affects performance on conjunction visual search, a more difficult task that requires feature binding and possibly the involvement of higher-level attention processes. Deficits in visual search may affect day-to-day functioning in people with amblyopia.

Attention in visually typical and amblyopic children

“…Our reaction times are in the range of or perhaps slightly slower than those reported by Roberts et al (2016) for amblyopic adults on a comparable task. They are also comparable with those reported by Tsirlin et al (2018) for their large-set size conjunction search condition and Suttle et al (2011); each of these two studies reported reaction time elevation with amblyopic viewing. Therefore, we do not believe that our failure to find a difference in reaction time between groups in our study is because our children were not responding quickly enough.…”

“…(2016) for amblyopic adults on a comparable task. They are also comparable with those reported by Tsirlin et al. (2018) for their large-set size conjunction search condition and Suttle et al.…”

“…They found elevated amblyopic eye size thresholds, especially for large set sizes. More recently, another study measured conjunction search performance (Gabor patch spatial frequency and orientation) in amblyopic observers, explicitly controlling for low-level visual losses, under central fixation (Tsirlin et al, 2018). They found longer reaction times and lower accuracy as the number of elements in the display increased for all observers and viewing conditions in conjunction search, as expected, but the impairment was greater with the amblyopic eye viewing under the higher load conditions.…”

“…For example, under conditions such as multiple-object tracking or conjunction visual search, differences between observers only become apparent with large sets of distractors (Ho et al, 2006;Neri & Levi, 2006). Delayed or overall slower processing of relevant compound stimuli may explain the increased reaction times found for amblyopic observers in conjunction visual search and Stroop performance (Tsirlin et al, 2018;Zhou et al, 2015). These explanations would support the existence of deficiencies in effectiveness of attentional deployment or perhaps limitations in attentional capacity on complex or high-demand tasks.…”

Dichoptic Attentive Motion Tracking is Biased Toward the Nonamblyopic Eye in Strabismic Amblyopia

“…51 Other studies have used psychophysics to investigate attentive processing in amblyopia under monocular viewing conditions, with mixed results. Impairments have been reported in multiple-object tracking, 52,53 conjunction visual search, 54 and attentional blink tasks, 55 suggesting an attention deficit associated with not just the amblyopic but also the fellow eye, that affects both spatial and temporal components of visual attention. On the other hand, studies using attentive cueing paradigms in humans 56,57 and primates 58 have reported that attentional modulation is comparable to a normal visual system.…”