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Retinal Responses to Stimulation with a Photovoltaic Prosthesis

Abstract

Here we present the design and characterization of a fully wireless subretinal visual prosthesis, which delivers electrical stimulation via photovoltaic pixels, illuminated with pulsed near infrared light (880-915 nm). In this dissertation I characterize the retinal responses to this photovoltaic retinal prosthesis in-vitro. The results show that the devices preserve crucial features of natural vision, including adaptation to static visual scenes, flicker fusion, and transient responses to changes in luminance. Arrays comprised of hexagonal pixels that are each either 140 μm or 70 μm wide safely elicit retinal responses in-vitro, as well as cortical responses in-vivo, in both healthy and diseased animal models. The stimulation takes advantage of the existing retinal network and is highly localized, restoring vision in blind rats at up to half the normal visual acuity. The retina is able to respond to high-frequency stimulation (20Hz), approaching that of natural visual scenes, surpassing other retinal prostheses that fail to reliably produce visual responses above 7Hz. The ability of this device to reliably produce retinal responses to high-frequency images is a promising indication of a new level of patient satisfaction that might be obtained during the first human clinical trials taking place later this year.

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