The Boston Retinal Implant

Abstract

The Boston Retinal Implant Project has developed a subretinal, hermetically-enclosed, chronically-implantable vision prosthesis to restore some useful vision to people with degenerative retinal diseases, especially retinitis pigmentosa and age-related macular degeneration. Our implant attaches to the outside of the eye, with only the electrode array entering the eye, carrying over 256 independently-configurable retinal stimulation channels. Our device receives wireless power and data from an inductive link, and inbound data includes image information in the form of stimulation commands containing current amplitudes and pulse widths. Outbound data includes status information on the implant and measurements of electrode voltages. A custom-designed integrated circuit chip is packaged in an 11 mm-diameter titanium case with a ceramic feedthrough, attached to the side of the eye. The chip decodes the stimulation data, creates biphasic, charged-balanced current pulses, and monitors the resulting voltages on the stimulating electrodes. The electrode array is a thin, flexible, microfabricated film carrying hundreds of wires to exposed electrodes in the eye. The electrodes are coated with sputtered iridium oxide film to allow much greater charge transfer per unit area by means of reversible faradaic reactions. The Boston Retinal Implant is being manufactured and tested in pre-clinical trials for safety, with plans to begin clinical trials soon.