Retinal prostheses have the potential to restore some level of visual function to blind individuals. While visual prosthetic devices for the optic nerve and visual cortex also have potential application, the retinal approach offers the advantage of relatively accessible retinal neurons in the back of the eye. Biological studies have demonstrated biocompatibility of implantation and stimulation and have investigated retinal response to stimulation. Recent clinical trials have shown that a prototype epiretinal implant, despite having few electrodes contacting the retina, still allows test subjects to perform simple visual tasks. Ongoing engineering research is focusing on the fabrication of a high-resolution implant