Scientists are helping blind people see again, one pixel at a time. If all goes well, an artificial retina could be commercially available within three years. Artificial retinas have been successfully implanted in six patients, allowing them to see light and detect motion, researchers announced at the 2005 annual meeting of the Association for Research in Vision and Ophthalmology in Fort Lauderdale, Florida. Developed by researchers from the University of Southern California and the Doheny Eye Institute, the artificial retina pairs a tiny electronic eye implant with a video camera mounted on a pair of sunglasses. The implant, a four-by-four grid of electrodes, connects to damaged photoreceptors -- rods and cones -- on the patient's retina. The electrodes stimulate the photoreceptors, which transmit signals to the brain through the optic nerve. Signals from the sunglasses-mounted videocam take a rather circuitous route to the electrodes. The camera translates the field of view into electrical impulses that are transmitted wirelessly to a microchip located behind the ear. In turn, the microchip is connected to the retinal implant by wires under the skin. The system -- known as the Argus, after the mythological Greek god who had 100 eyes -- works only with patients with degenerated rods and cones, a condition often caused by disease. It will not help people with damaged optic nerves or other types of blindness. "These patients are blind because they don't have the photodetectors," said lead researcher Dr. Mark Humayun, a professor of ophthalmology and biomedical engineering at the University of Southern California. "The implant jump-starts the remaining cells. You're effectively coupling a blind person with a wearable camera." According to Humayun, all the six test patients, who had been totally blind, are now able to detect light and sense motion.