Ângela Gomes Tomaz¹, Bilge Sayim², Dennis M. Levi¹; ¹Herbert Wertheim School of Optometry & Vision Science, University of California Berkeley, Berkeley, USA, ²Laboratoire de Sciences Cognitives et Psycholinguistique, Département d'Études Cognitives (DEC), École normale supérieure (ENS), CNRS, Paris, France

Redundancy masking (RM) is the reduction of perceived number of items in repeating patterns (e.g., perceiving two lines when three are presented). RM occurs predominantly with regular arrangements of items, suggesting that regularity is a necessary condition for RM. In amblyopia, a neurodevelopmental disorder of spatial vision characterized by reduced visual acuity, observers have impaired spatial localization and noisy positional perception. As accurate (relative) localization is required to extract stimulus regularity, we hypothesized that RM would be reduced in amblyopia. Here, we explored the extent to which the amblyopic visual system compresses information in RM across the visual field. Seventeen observers (5 with amblyopia, 11 controls) were presented with arrays of 3, 4 or 5 lines for 100 ms (randomly to the right or left visual field). Lines were presented binocularly at 2.5°, 5°, 10°, or 20° eccentricity, as well as monocularly to the non-dominant/amblyopic eye at 2.5° and 5° (eye order counterbalanced). Eye-tracking ensured peripheral presentation of the stimulus. Five inter-line spacings were used from 1.50° to 4.30° in steps of 0.7° (at 20°eccentricity). Line size and inter-line spacings were linearly scaled at the other eccentricities and confirmed to be above observers’ minimum angle of resolution at each eccentricity. Observers’ task was to report the number of lines perceived. Preliminary results showed stronger RM at 20° eccentricity compared to all other eccentricities, and for the smallest spacing compared to all other spacings (and the second smallest compared to the largest). We found a strong trend for weaker RM across the visual field in the amblyopic compared to the control group. Our findings show that RM increases with eccentricity, and may be reduced in amblyopia hinting at a potential advantage in amblyopic visual processing.

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.