Electrical Stimulation of the Human Retina

Abstract

The visual prosthesis being developed will provide useful vision to people blind because of photoreceptor loss due to retinal degenerative diseases such as age related macular degeneration (AMD) and retinitis pigmentosa (RP). A retinal prosthesis will replace photoreceptor function with an electronic device. In a healthy retina the pho- toreceptors initiate a neural signal in response to light. Photoreceptors are almost com- pletely absent in the retina of end-stage RP patients and in the macular region of AMD patients. However, cells to which photoreceptors normally synapse, (i.e. bipolar cells) survive at high rates. In blind volunteers, we have shown that controlled electrical signals applied with a microelectrode positioned near the retina elicit the perception of a spot of light that correlates both spatially and temporally to the applied stimulus.^1,2 When multiple electrodes are activated in a two dimensional electrode array, a number of small spots of light are perceived by the patient(s) which when viewed together form an image representative of the pattern of active electrodes. Thus similar to how an image is formed by a dot-matrix printer, when controlled pattern electrical stimulation of the remaining retinal neurons is coupled with an extraocular image acquisition and transmission system, it could allow blind patients to regain form vision.