High-Resolution Opto-Electronic Retinal Prosthesis: Physical Limitations and Design

Abstract

Electrical stimulation of the retina can produce visual percepts in blindpatients suffering from macular degeneration and retinitis pigmentosa (RP).However, current retinal implants provide very low resolution (just a fewelectrodes), whereas many more pixels would be required for a functionalrestoration of sight.This article presents a design of an optoelectronic retinal prostheticsystem with a stimulating pixel density of up to 2500 pix/mm2(corre-sponding geometrically to a maximum visual acuity of 20/80). Requirementson proximity of neural cells to the stimulation electrodes are described asa function of the desired resolution. Two basic geometries of subretinalimplants providing required proximity are presented: perforated membranesand protruding electrode arrays.To provide for natural eye scanning of the scene, rather than scanning witha head-mounted camera, the system operates similarly to “virtual reality”devices. An image from a video camera is projected by a goggle-mountedpulsed infrared LCD display onto the retina, activating an array of poweredphotodiodes in the retinal implant. The goggles are transparent to visiblelight, thus allowing for the simultaneous use of remaining natural visionalong with prosthetic stimulation. Optical delivery of visual informationto the implant allows for real-time image processing adjustable to retinalarchitecture, as well as flexible control of image-processing algorithms andstimulation parameters.