A "bionic eye" may one day help blind people see again, according to US
Researchers who have successfully tested the system in rats. The eye implant - a 3-millimetre-wide chip that would fit behind the retina - could be a dramatic step above currently available technology.

About 1.5 million people worldwide have a disease called retinitis pigmentosa, and 700,000 people in the western world are diagnosed with age-related macular degeneration each year. In both degenerative diseases, retinal cells at the back of the eye that process light gradually die.

For the device to work, the microchip would have to be implanted behind the retina of the blind person. The patient would wear goggles mounted with a small video camera. Light enters the camera, which then sends the image to a wireless wallet-sized computer for processing. The computer transmits this information to an infrared LED screen on the goggles. The goggles reflect an infrared image into the eye and on to the retinal chip, stimulating photodiodes on the chip. The photodiodes mimic the retinal cells by converting light into electrical signals, which are then transmitted by cells in the inner retina via nerve pulses to

the brain. These are then sent back to the glasses and wirelessly on to a receiver just under the surface of the front of the eye. Working on the bionic eye, these implants have very low resolution.

OVERVIEW OF BIONIC EYE