Electric current
Daniel Palanker and his group at Stanford University have developed a photovoltaic retinal prosthesis that includes a subretinal photodiode array and an infrared image projection system mounted on video goggles. Images captured by video camera are processed in a pocket PC and displayed on video goggles using pulsed near-infrared (IR, 880–915 nm) light. These images are projected onto the retina via natural eye optics, and photodiodes in the subretinal implant convert light into pulsed bi-phasic electric current in each pixel. Electric current flowing through the tissue between the active and return electrode in each pixel stimulates the nearby inner retinal neurons, primarily the bipolar cells, which transmit excitatory responses to the retinal ganglion cells.