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Amy C. Nau, Christopher N. Fisher, Christine Pintar, Gail Engleka; Vision Based Psychophysical Tests Can be Used with Sensory Substitution Device (Brainport). Invest. Ophthalmol. Vis. Sci. 2011;52(14):461.
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© ARVO (1962-2015); The Authors (2016-present)
To determine if computer based tests of low visual function can be used to evaluate a sensory substation device (BrainPort, Wicab Inc, Madison WI). The Basic Assessment of Light Motion (BaLM), the Basic Assessment of Grating Acuity (BaGA) and the Friberg Acuity Test (FrACT) were developed to test rudimentary of visual functions (Bach). The BrainPort is a sensory substitution device which allows the blind to perceive their environment by means of a glasses-mounted camera, paired with a 400 electrode tactile array placed on the tongue. There have been no prior attempts to rigorously evaluate the visual function conferred by the BrainPort.
We report a consecutive case series examining if psychophysical assessments could be successfully run using a device which, while allowing perception of the environment, completely bypasses the ocular components of the visual system. Nineteen subjects (n=15 blind and n=4 blindfolded, sighted controls) were evaluated with 9 computer screen tests from 3 programs: BaGA, BaLM, and FrACT. The tests included: light perception, time resolution, location, motion, grating acuity, Landot C (black letter on white surround and inverse) and contrast (dark letter on light surround and inverse). The tests were performed at baseline and repeated using the BrainPort after 15 hours of training. All tests were performed in a darkened room with the subject seated .5m away from a computer screen.
Significant increases in mean percentage of correct responses were found between baseline and post-training for 5 tests using paired t-tests: Grating acuity +39.8% (p < 0.001), Light perception +34.37% (p < 0.001), Time resolution +9.6% (p = 0.044), Location +30.6% (p < 0.001), Tumbling E(white letters on black surround) +0.0016 DVA (p = 0.046). The remaining six tests did not attain statistically significant improvements over baseline, but were able to be tested with equal success. Motion +1.9% (p = 0.542), Landot C (black letter on white surround) +0.000075 (p = 0.302), Landot C (white letter on black surround) +0.0036 (p = 0.126), Tumbling E (black letter on white surround) +0.00023 (p = 0.210), contrast tests yielded zero percent change for all subjects.
Our results show these tests are well suited to evaluate the sensing capabilities of the BrainPort. The tests without statistically significant results approached the threshold of the current BrainPort electrode array. These tests will be useful in the evaluation of future improvements to the BrainPort and possibly other assistive technologies. They are also easy to conduct, mobile, and inexpensive.
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