The Alpha IMS developed by researchers at the university of Tubingen, Germany, detects light coming into eyes via electrodes placed within the patients retina. This is fed into a microchip that sends signals to the brain. The brain then processes these signals, as it would from a healthy eye and the person can see a black and white image. A dial is fitted just behind the ear to adjust the brightness. Alpha IMS is powered by a wireless pocket battery.
In clinical trials so far 9 patients were fitted with Alpha IMS of which in 8 patients it was successful. There is another device Argus II that relies on an external camera to transmit data to the implant in the retina. Due to this the Argus II wearers have to turn head to look from side to side, where as the Alpha IMS wearers can look by moving their eyes. As per patients from close up, they can detect smiles, whether someone is wearing glasses or not, details such as signs on doors. At Far distances, patients can make out houses, trees. They could also detect cars identified by moving bright headlights.
In normal eyes the outer layer of the retina convert light into an electrical signals that is send to the brain. The normal function of retina can be lost due to various eye related diseases which turn the person blind. This can be corrected by these devices.
source : newrisingmedia