'Bionic eye', also called a Bio Electronic eye, is the electronic device that replaces functionality of a part or whole of the eye. It is still at a very early stage in its development, but if successful, it could restore vision to people who have lost sight during their lifetime. The principle of a bionic eye is very similar to that of the bionic ear. Bionic eyes and ears both work by stimulating nerves, which are activated by electrical impulses. In both cases the patient has a small device implanted into the body that can receive radio signals and transmit those signals to nerves.
The healthy human eye has many millions of biological solar cells in the retina, called rods and cones that convert light into electrical signals, which are then sent along the optic nerve to the brain where images are formed. In cases where the retina fails, the nerves behind the retina, which carry electrical impulses, still function. Many people are blind because of malfunctioning rods and cones. Retinitis pigmentosa and macular degeneration are examples of two such disorders. Retinitis pigmentosa tends to be hereditary and may strike at an early age, while macular degeneration mostly affects the elderly.
Currently researchers around the world are exploring ways of restoring sight to people with retinal degeneration in two methods. One method uses a small video camera-equipped device to capture images, encode them and send them into the eye implant (a silicon chip inserted into the eyeball) via a laser beam that also powers the chip's solar cell. Photo sensors convert the light and images into electrical impulses, which charge a plate that stimulates the nerves and transmits visual information to the brain. The laser and camera can easily be mounted on eyeglasses without having to wear bulky headgear.
In another method, microchips replace the eye's malfunctioning natural sensor with an artificial sensor (silicon retina), manufactured on a piece of silicon. When the chip is implanted into the back of the eye and light strikes those solar cells, the light is converted into electrical signals that travel via the optic nerve to the brain and are interpreted as an image.
Development continues to gauge the compatibility of silicon with living tissue as silicon is toxic to the human body and reacts unfavourably with fluids in the eye, and to make the microchips as non-invasive to the eye as possible. Preliminary tests are on going on the ceramic detectors for biocompatibility, and they appear to be totally stable.
Source : The Hindu