The German company Retina Implant AG has developed an implantable microchip that's installed directly under the retina, which stimulates intact inner nerve cells to produce artificial vision. The chip measures 9 millimeters long and wide, and is only 0.1 millimeters thick. Around 1,500 light-sensitive photodiodes, amplifiers, and electrodes in the chip absorb light and convert it into the electricity that activates the nerve cells. A series of transmitter coils buried under the skin behind the ear power the chip. One of its main advantages is the lack of external components, such as the tiny video cameras and transmitters that are used in most epiretinal (over the retina) approaches.
The 11 patients who participated in Retina Implant's first clinical trial, which began in 2005, saw marked improvements in their abilities to read and recognize objects and outlines. Initially all that the chip-assisted eyes can detect are lines, but the brain quickly learns how to piece them together in order to recognize words and images. A more recent study from Retina Implant showed even greater promise, with videos showing one previously blind patient who could identify apples and bananas, and who could tell when his name had been misspelled.