Fig. 2

Main approaches for the design of a visual prosthesis. a Schematic diagram of a retina cross-section showing three methods of stimulating the output cells of the eye: 1, Epiretinal; 2, Subretinal and 3, Suprachoroidal. b Optic nerve based visual prosthesis. c Stimulation of the lateral geniculate nucleus of the thalamus (LGN). d Cortical approach. In general, all the approaches share a common set of components: a camera to capture images, generally mounted on more or less standard glasses; a second stage that transform the visual scene into patterns of electrical stimulation and transmits this information through a radio-frequency link to the implanted device, and an electrode array implanted at some level in the visual pathways which has to be located near the target neurons