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V. Chowdhury, J.W. Morley, M.T. Coroneo; Extraocular Retinal Stimulation for a Visual Prosthesis . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1489.
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Purpose: To demonstrate the feasibility of extrocular retinal stimulation for a visual prosthesis. Methods: In anaesthetised cats, electrical stmulation of the retina was carried out with prototype electrodes sutured to the scleral surface of the globe. Evoked cortical responses were recorded from surface disc electrodes placed in a subdural location over the primary visual cortex. Stimuli consisted of single biphasic, current–controlled pulses. Results: Extraocular stimulation of the temporal retina elicited evoked cortical responses that were higher in the ipsilateral visual cortex compared with the contrlateral visual cortex. This interhemispheric variability was used as a measure of the focality of retinal excitation with extraocular electrodes. Thresholds for retinal excitation with extraocular electrodes were determined. Conclusions:Extraocular electrodes are a new approach to developing a low resolution visual prosthesis to restore basic visual sensations to blind patients. The results of the study demonstrate that localised retinal activation can be achieved with sclerally placed electrodes, and that the thresholds for extrocular stimulation occur at intensities within safe limits for chronic neural stimulation.
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