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Paulette Lieby, Nick Barnes, Chris McCarthy, Adele F. Scott, Viorica Botea, Janine G. Walker; Mobility Experiments Using Simulated Prosthetic Vision With 98 Phosphenes Of Limited Dynamic Range. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5539.
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Using simulated prosthetic vision (SPV) and a mobility course including overhanging obstacles, we evaluate the effectiveness of a 98 phosphenes, low dynamic range retinal implant. (Bionic Vision Australia's first prototype retinal prosthesis will have 98 electrodes). Effectiveness was defined as a percentage of preferred walking speed (PPWS) larger than 50%.We investigated the performance of two visual representations: Intensity (visual field luminance); and, Depth (relative depth of the visual field). Depth provides an example of an alternative visual representation that is robust to low contrast environments.
Four normally-sighted participants (20/20, Pelli-Robson>=1.95) traversed a mobility course using mobile SPV showing 98 phosphenes on a hexagonal grid and centrally displayed identically to both eyes. Each phosphene was rendered over 8 levels of brightness. The study had a double-blind randomised factorial
In the test phase, mean PPWS for both Intensity (n=56) and Depth (n=110) was significantly larger than 50% (p<=0.028). For both Intensity and Depth, mean PPWS was significantly greater in the test phase compared to the training phase (p<=0.035); indicating that participants became more adept to both visual representations over time. Across all sessions, Intensity (n=104, mean PPWS=61%) and Depth (n=204, mean PPWS=50%) had significantly higher PPWS than no meaningful visual information (n=19, mean PPWS=27%, p<0.001). Intensity had significantly higher mean PPWS than Depth (p<0.001).
Visual information representing scene contrast or depth cues using simulated prosthetic vision showing 98 phosphenes under low dynamic range conditions may be used for effective mobility.
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