Dichoptic Visual Search at Varied Fellow Eye Contrasts and Visual Function Deficits in Amblyopia.

Purpose: This study uses dichoptic visual search and psychophysical visual function data to understand factors that impact amblyopic eyes' ability to perceive the stimulus while the fellow eye (FE) contrast is reduced under dichoptic viewing in children and adults. Methods: Twenty-three amblyopic (anisometropic = 11, strabismic/mixed = 11) and 14 control participants performed visual search and spot-the-difference tasks during monocular and dichoptic viewing with amblyopic eye (AE) contrast held constant at 100% while FE contrasts varied at 100%,50%,25% and 10%. Accuracies and reaction times were analyzed and correlated with visual acuity deficit of amblyopic eye, stereoacuity and suppression. Results: Amblyopic participants showed reduced accuracies and longer reaction times in visual search and spot-the-difference tasks. Reducing the FE contrast improved their ability to identify the targets and differences with greater improvement observed for anisometropic than strabismic subjects. However, participants with higher suppression, visual acuity deficits in the AE, and stereoacuity deficits faced greater difficulties, with reduced accuracies and reaction time, especially at high FE contrasts. For tasks requiring comparison between AE and FE regions to spot-the-differences, deficits in AE visual acuity, suppression and stereoacuity were linked to reduced accuracy and increased reaction times, even at 10% FE contrasts. Conclusions: The study highlights the challenges amblyopic participants face in dichoptic tasks, particularly at high FE contrasts. Dichoptic contrast modulation holds promise in enhancing the perception of the AE with responses varying by visual function deficits. It also highlights that quantification of perception of the AE in dichoptic environment with tools such as visual search may allow tailoring of passive video-based dichoptic therapies.