Journal of Rehabilitation Research and
Development Vol. 36 No. 4, October 1999
Abstract - Subretinal implantation of semiconductor-based photodiodes: Progress and challenges
Neal S. Peachey, PhD; Alan Y. Chow, MD
Edward Hines Jr. VA Hospital, Hines, IL 60141; Loyola University Chicago, Maywood, IL 60153; Optobionics Corporation, Wheaton, IL 60187; LSU Eye Center, New Orleans, LA 70112
Retinal diseases that result in photoreceptor degeneration may spare the inner retinal layers. This review concerns a prosthetic approach to restoring visual function through the use of a semiconductor-based microphotodiode array implant, designed to be placed under the neural retina in the subretinal space. The fundamental idea is that current generated by the device in response to light stimulation will alter the membrane potential of overlying neurons and thereby activate the visual system. Initial acute studies indicated that the implant will function in the subretinal space in the absence of an external power supply. More recent and ongoing studies involve chronic subretinal implantations in normal animals. Post-operative studies have demonstrated that implant function will persist for many months. These chronic studies have also assessed the biocompatibility of the implant. Photoreceptors are lost directly overlying the implant, due to the blockade of choroidal circulation to the outer retina by the solid disk device. In comparison, the inner retina maintains its characteristic lamellar structure. Away from the implant site, the retina retains normal anatomy and function. Future studies are needed to determine whether the implant can establish a functional connection to the inner retina and to determine the quality of this connection.
Key words: age-related macular degeneration, blindness, microphotodiode, retina prosthesis, retinitis pigmentosa, semiconductor.