Development of a high‐resolution optoelectronic retinal prosthesis

Abstract

Electrical stimulation of the retina can produce visual percepts in blind patients suffering from retinal degeneration. Current retinal implants have just a few electrodes, whereas thousands of pixels would be required for functional restoration of sight. We present a design of an optoelectronic retinal prosthetic system with a pixel density up to 2,500 pix/mm 2 (corresponding geometrically to a maximum visual acuity of 20/80). Design of such prosthesis presents several major challenges: (a) To avoid cross‐talk between pixels, metal erosion and overheating of tissue during chronic stimulation the electrodes need to be located very close to cells; (b) To allow for natural eye scanning of images, information delivered to the implant should be linked to eye movements; (c) To adjust the stimulation map to retinal architecture, real‐time location‐dependent image processing will be required. Intimate proximity between electrodes and cells (~ 10 μm) is achieved using migration of retinal cells into 3‐dimensional subretinal implants. Microfabricated arrays consist of either chamber or pillar electrodes 10 μm in diameter and 50 ‐ 70 μm in height. Processed video frames are projected from a goggle‐mounted pulsed infrared display onto the retina, activating the photosensitive pixels in the retinal implant. Each pixel converts local light intensity into a biphasic pulse of current using a common bi‐phasic pulsed power line. An eye tracking system mounted on the same goggles monitors the position of the retinal implant and adjusts the image processing between the camera and the IR goggles at a rate of 30 f/s.