Abstract
Sensory Substitution Devices (SSDs) convey visual information through sounds or touch, thus theoretically enabling a form of visual rehabilitation in the blind. However, for clinical use, these devices must provide fine-detailed visual information which was not yet shown for this or other means of visual restoration. To test the possible functional acuity conveyed by such devices, we used the Snellen acuity test conveyed through a high-resolution visual-to-auditory SSD (The vOICe). We show that congenitally fully blind adults can exceed the World Health Organization (WHO) blindness acuity threshold using SSDs, reaching the highest acuity reported yet with any visual rehabilitation approach. This demonstrates the potential capacity of SSDs as inexpensive, non-invasive visual rehabilitation aids, alone or when supplementing visual prostheses.
Highlights
Blindness is a highly limiting disability, affecting tens of millions of individuals worldwide [1]
Snellen original stimuli sizes are reported in Snellen fractions, physical letter size and logMar, a linear scale which expresses the logarithm of the minimal angle of resolution [24]. doi:10.1371/journal.pone.0033136.t002
Our findings suggest that early and congenitally blind individuals using auditory substitution device (SSD) can retrieve detailed visual information at a much higher resolution than previously demonstrated with any other sight rehabilitation approach
Summary
Blindness is a highly limiting disability, affecting tens of millions of individuals worldwide [1]. The newest subretinal prosthesis under development technically has 1500 pixels, but provides a much lower than expected functional acuity, with a maximal measurable acuity of only 20/1000 [4]; the smallest letter implant patients can see at 20 feet could be seen by a normal eye at 1000 feet (i.e. they can discern only extremely large letters). Visual rehabilitation may alternatively be achieved using Sensory Substitution Devices (SSDs [5]) which enable the blind to ‘see’ using their other senses These focused on tactile-tovisual SSDs [6], and interestingly, their maximal technical resolution was only 144 pixels at the time, they enabled better acuity than the highest 1500-electrode technical resolution retinal implant under development today
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