Yi xu¹ (), Navya Sreeram¹, Rob Chun¹, Roksana Sadeghi², Chau Tran³, Will Gee³, Gislin Dagnelie⁴, Ione Fine^5,6, Arathy Kartha ¹; ¹Department of Biological and Vision Sciences, SUNY College of Optometry, ²University of Berkeley California, Herbert Wertheim School of Optometry, ³BaltiVirtual , ⁴Wilmer Eye Institute, Johns Hopkins School of Medicine, ⁵University of Leeds, Leeds, UK, ⁶University of Washington, Seattle

Individuals with normal vision (NV) integrate information from their senses close to optimally. People with ultra-low vision (ULV) traditionally undergo blind rehabilitation, where they are taught to rely on tactile and auditory cues to compensate for their vision loss. This rehabilitation might help blind individuals to integrate optimally. Alternatively, being taught to ignore vision and rely on the other senses might lead to sub-optimal integration when there is remaining useful vision. Fourteen NV wearing ULV filters (sULV; 2.05 ±0.17 logMAR) and one ULV with advanced retinitis pigmentosa (2.0 logMAR, visual field <10 degrees) completed a spatial localization task in a virtual reality environment under unimodal (V = visual, A = auditory) and bimodal (VA = visual-auditory) conditions. Two flashing and/or ringing phones appeared in sequence in different locations of the central field (-4.5 to 4.5), and participants reported whether the first was to the left or right of the second. Percent correct as a function of the stimulus separation was fit using a cumulative Gaussian distribution. The unimodal standard deviations, 𝜎, for the unimodal conditions (V and A), were used to predict optimal performance in the multimodal (VA) condition. For the sULV, mean 𝜎 was V = 1.5 ± 0.4, A = 7.6 ± 6.8, VA = 1.9 ± 0.5 with an optimal predicted VA = 1.5. There was a significant difference between predicted and empirical VA (paired t-test; t (13) = 3.3; p=0.003), showing that sULV were non-optimal in integrating visual and auditory cues. For the ULV participant, 𝜎 was V = 3.1, A = 6.1, and VA = 2.2, with an optimal predicted value of 2.7. These suggest that through years of living with her condition, the native ULV may have learned to integrate optimally, contrary to sULV, who had little time to adapt to filters.