In a healthy eye, the rods and cones on the retina convert light into tiny electrochemical impulses that are sent through the optic nerve and into the brain, where they’re decoded into images. If the
Retina no longer functions correctly—due to conditions such as Retinitis pigmentosa
(RP) or Age-related Macular degeneration (AMD)—the optic nerve can be given information from an artificial source bypassing the photoreceptor mechanism in the path. Capturing images and converting them into electrical signals is the easy part. The much trickier part is wiring the input into a person’s nervous system. Retinal implants currently being tested pick up radio signals from a camera mounted on a pair of glasses and then directly stimulate the nerve cells behind the malfunctioning rods and cones. The system would directly stimulate the layer underneath the dead photoreceptor, with resolution corresponding to 20/80 visual acuity. The eye of a fly forms a very fuzzy image of the world, and its brain is only the size of a grain of rice, yet flies must obviously have an exquisite sense of visual motion because they are able to see well enough to avoid being swatted and they are able to perform precise landing maneuvers.
Developing a motion-sensing chip for use as a bionic eye could also have application in other areas, for example, as powerful type of anti-collision sensor in motor vehicles, and as optical gyroscopes for miniature aircraft.
