Electrophysiological Function Tests of Epi- and Subretinal Implants
Schanze T.1, Eckhorn R.1, Stett A.2, Eysel U.3, Kisvarday Z.3, Zrenner E.4, Hesse L.5
1NeuroPhysics Group, Univ Marburg, 2NMI, Reutlingen, 3Neurophysiology Group, Univ Bochum, 4Eyeclinic, Univ Tübingen, 5Eyeclinic, Univ Marburg
Purpose: Animal-tests of epi- and subretinal implants that have been designed to replace the function of degenerated photoreceptors in diseases like retinitis pigmentosa and age-related macular degeneration.
Method: In-vitro tests were performed with isolated retinae from chicken and RCS rats by recording of retinal responses to electrical stimulation. In-vivo function tests were performed in acutely and chronically prepared anaesthetized cats, minipigs, and rabbits. Surgery was accomplished prior to in-vivo testing of complete implants and wire-activated retinal electrode arrays. Responses to electrical retina stimulation were recorded from the optic nerve and from primary visual cortex (areae A17/18) either with intracortically positioned fibre electrodes, epidurally placed electrodes, or by optical imaging. From the stimulus-response data we estimated advantageous stimulation parameters, calculated the retino-cortical information transfer, and estimated the spatial and temporal resolution achievable with electrical retina stimulation.
Results: In-vitro and in-vivo experiments demonstrated how stimulation threshold
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