Brooke Lim¹, Anna Kosovicheva¹; ¹University of Toronto Mississauga

Many everyday tasks rely on binocular vision, which is impaired in individuals with amblyopia. Impairments in visual-spatial processing normally characterize amblyopia, but previous work has shown deficits in temporal processing as well, including processing delays in the amblyopic eye. Many techniques have been developed to measure interocular timing delays behaviourally by showing different images to the two eyes and recording participant responses. However, agreement between these measures has not been previously investigated. We compared four different assessment measures in normally-sighted observers: depth-based judgments (using the Pulfrich effect), interocular flicker integration, reaction time to monocular targets, and interocular temporal order judgments. Stimuli were presented using a high-speed projector with passive polarized filters (240 Hz per eye), enabling precise temporal control for dichoptic presentation. We also included a measure of sensory eye dominance to determine how eye dominance is related to each of the timing-based measurements. Pairwise comparisons of temporal delays measured across methods showed that the best-correlated pair of measures was between interocular flicker integration and temporal order judgements (r = 0.50). For each measure, we additionally calculated the average correlation between it and the remaining three measures. The Pulfrich effect was the best-correlated measure for examining timing delays between the eyes (Fisher Z = 0.24). In contrast, the measure that was least correlated with the other three measures was reaction time (Fisher Z = 0.09). Eye dominance was not correlated with the four temporal delay measures (Fisher Z = -0.01). Together, these results suggest that methods that rely on binocular integration are more reliable than monocular measurements. This highlights the importance of selecting appropriate tools for measuring interocular delays, and that suggests that combining specific methods may better characterize temporal delays seen in visual impairments.

Acknowledgements: This work was supported by an NSERC Discovery Grant to AK, and a UTM Undergraduate Research Grant to BL.