Epi-retinal prosthesis

Abstract

Retinitis pigmentosa (RP) and age-related macula degeneration (AMD) lead to the degeneration of photoreceptors, resulting in a significant visual deficit for the afflicted individual [1]. Research is proceeding to investigate the feasibility of replacing the function of the photoreceptors with an electronic device [2, 3]. The photoreceptors initiate a neural signal in response to light. The experiments to be discussed investigate the possibility of using electrical signals (generated by a retinal prosthesis) to initiate a neural response in the remaining cells of the retina. Results from both animal and human research conducted over the past decade have established the following: Intraocular stimulating electrodes can evoke focal responses that correlate with the stimulus position and timing [4–6], the inner retina in RP and AMD is relatively unharmed even when the outer retina is severely degenerated [7–9], and a device can be implanted on the surface of the retina without causing significant damage to the retina [10, 11]. Based on these preliminary trials, an FDA approved clinical trial was intiated to assess safety of implantation of an epiretinal device in humans blind from retinitis pigmentosa. 2 human volunteers have used permanently implanted devices to detect ambient light and sense motion. Based on these encouraging results, the current focus is being shifted from feasibility studies to the development of an implantable, electronic device, which will be capable of stimulating the retina at hundreds of individual points.