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Vision Res. 2003 Apr;43(9):1091-102.

Position, size and luminosity of phosphenes generated by direct optic nerve stimulation.

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Neural Rehabilitation Engineering Laboratory, Université Catholique de Louvain, 54, Avenue Hippocrate, Box UCL 54.46, B-1200, Brussels, Belgium.


Pulses of low intensity current, delivered through a cuff electrode chronically implanted around the optic nerve of a blind retinitis pigmentosa patient generate visual sensations. These phosphenes are obtained at lower thresholds for a train of stimuli than for single pulses, which suggests the existence of a spatial and temporal integrating mechanism. The perceptions are much smaller than those predicted from model simulations. A set of equations are derived which show the effect of pulse current, duration, number and frequency on the position, size and, to some extent, luminosity of the resulting phosphenes.

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