Bilge Sayim¹, Taylor Lui², Dennis M. Levi², Ângela Gomes Tomaz²; ¹Sciences Cognitives et Psycholinguistique, Département d'Études Cognitives (DEC), École normale supérieure (ENS), CNRS, Paris, France, ²Optometry & Vision Science, University of California Berkeley, Berkeley, USA

In amblyopia, a neurodevelopmental disorder of spatial vision, observers have impaired spatial localization. Redundancy masking (RM) –the reduction of the perceived number of items in repeating patterns– has been found to strongly depend on stimulus regularity, with strongest RM in regular arrangements and weak or no RM in irregular arrangements, suggesting that regularity is a necessary condition for RM. Here, we explored whether RM exists in amblyopia and, as accurate (relative) localization is required to extract stimulus regularity, we hypothesized that RM would be reduced in amblyopia. Six observers with amblyopia (2 strabismic, 1 anisometropic and 3 mixed) and twelve controls were presented with arrays of 3, 4 or 5 lines for 150 ms randomly to the left or right of fixation at 8° eccentricity. Line arrays were presented binocularly, as well as monocularly to either eye (while the other was patched). Five inter-line spacings were used from 0.45° to 1.38° in steps of 0.23°, all above observers’ minimum angle of resolution. The task was to report the number of lines perceived. Preliminary results showed weaker RM for observers with amblyopia compared to controls, and for the non-dominant/amblyopic eye compared to binocular presentation. RM at the largest spacing was weaker compared to all other spacings (except the second largest). The current findings support the notion that the atypical visual field asymmetries of RM–with the strongest RM along the horizontal meridian and no upper-lower asymmetry–may be due to spatial localization accuracy, which is greatest along the horizontal meridian. We suggest that, counterintuitively, higher magnitudes of positional noise (both internal and external) may improve performance, i.e., reduce RM.

Acknowledgements: Supported by a grant from the National Eye Institute awarded to Dennis M. Levi (R21EY030609) and a France-Berkeley Fund grant awarded to Dennis M. Levi and Bilge Sayim.