A model of ganglion axon pathways accounts for percepts elicited by retinal implants

BioRxiv : the Preprint Server for Biology
Michael BeyelerIone Fine


Degenerative retinal diseases such as retinitis pigmentosa and macular degeneration cause irreversible vision loss in more than 10 million people worldwide. Retinal prostheses, now implanted in more than 250 patients worldwide, electrically stimulate surviving cells in order to evoke neuronal responses that are interpreted by the brain as visual percepts ('phosphenes'). However, instead of seeing focal spots of light, users of current epiretinal devices perceive highly distorted phosphenes, which vary in shape not just across subjects but also across electrodes, resulting in distorted percepts. We characterized these distortions by asking users of the Argus retinal prosthesis system (Second Sight Medical Products, Inc.) to draw percepts elicited by single-electrode stimulation on a touchscreen. Based on ophthalmic fundus photographs, we then developed a computational model of the topographic organization of optic nerve fiber bundles in each subject's retina, and used this model to successfully simulate predicted patient percepts. Our model shows that activation of passing axon fibers contributes to the rich repertoire of phosphene shapes reported by patients in our psychophysical measurements, successfully replicating visual pe...Continue Reading

Related Concepts

Retinitis Pigmentosa
Low Vision
Visual Perception
Metaphosphoric acid

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