gms | German Medical Science

Artificial Vision — The 2nd Bonn Dialogue. The International Symposium on Visual Prosthesis

Retina Implant Foundation

19.09.2009, Bonn

Neurophysics of retinal visual prostheses

Meeting Abstract

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Artificial Vision – The 2nd Bonn Dialogue. The International Symposium on Visual Prosthesis. Bonn, 19.-19.09.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ri22

doi: 10.3205/09ri22, urn:nbn:de:0183-09ri226

Veröffentlicht: 30. November 2009

© 2009 Schanze.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen ( Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.



Blinds subjects with end-stage photoreceptor degenerative diseases such as retinitis pigmentosa and age-related macular degeneration have retinal neurons that are still intact. Without visual input, retinal ganglion cells spontaneously generate action potentials that are transmitted by their axons to higher visual centers. However, such non-visually driven activity can change the properties of the visual cortex. The goal of a retinal implant is to evoke retinal activation patterns that can be perceived as phosphenes which should be useful for vision restoration in blind subjects with degenerated photoreceptors. Despite much scientific and technical progress some important neurophysical questions are still pending. 1. What is the optimal electrode-neuron interface for selective, safe/low-threshold, and long-term stable stimulation? 2. What spatial, temporal, and intensity/contrast resolutions are obtainable with current retinal implant technology and are these resolutions sufficient to provide a detection or recognition of static objects and motion in visual scenes? 3. What electronic pre-processing of camera captured visual scenes and electrical stimulation parameters are useful and necessary to activate retinal neurons physiologically adequate and long-term stable for vision restoration? We summarize results of experiments obtained from anesthetized cats with intact visual systems, especially results concerning stimulation threshold as well as temporal and spatial resolution. We compare some of these results with results obtained from a clinical study performed by the German EPI-RET group with blind retinitis pigmentosa patients and conclude with respect to current and upcoming issues concerning design and testing of retinal implants.