To what extent can retinal prostheses restore vision?

After a general consideration of the various approaches to electrical stimulation of the retina, a thorough in vitro investigation of retinal responses to voltage-controlled stimuli is discussed within the context of the Alpha IMS subretinal implant (Retina Implant AG, Reutlingen, Germany). This is supplemented by a clinical trial interim report describing results obtained in 29 patients blind from retinitis pigmentosa who have received the Alpha IMS implant. It is concluded that the surgical procedure is safe and blind patients can benefit in visual tasks of daily life with this device that has meanwhile received approval for commercial use in Europe.