Bionic Eye-Helping the blind see again

Bionics is the application or adoption of methods and systems found in nature to modern technology. In other words, it can be considered as a form of biomimicry. The best example of a bionic device is the artificial cardiac pacemaker, which mimics the natural cardiac pacemaker by generating electrical impulses.

In the retina, which is the light sensitive layer of the eye, there are millions of light sensitive rods and cones (photoreceptors). These help in converting light into electrical impulses, which travel through the optic nerve to a specific area in the brain where images are formed. Any degeneration of these cells or disease of the optic nerve and brain can result in the loss of vision.

Retnitis Pigmentosa is a group of hereditary disorders, characterised by progressive loss of photoreceptors with the onset in childhood or middle age. Typically, the patient has night blindness, and some cases progress to total blindness. Age Related Macular Degeneration (AMD) has its onset generally in those over 60 years, and is characterised by degeneration mainly involving the macular area of the retina, which is the most sensitive for vision. Severe cases lead to blindness.

Exciting research is being carried out in many parts of the world in the development of the "Bionic Eye" which may enable blind people, especially with disorders like Retinitis Pigmentosa and Age Related Macular Degeneration (AMD) to see again.

The earliest experiment in eyes used silicone-based photodetectors, but since silicone is toxic to the body and reacts unfavourably, its use was abandoned.

Earlier this year, successful retinal implants were performed in some blind people. The device consisted of spectacles with miniature video cameras, which transmitted signals to a retinal implant. The transmitted visual signals received by the video camera travels to the retinal implant, which contains electrodes. The signal stimulates any remaining healthy retinal cells, which in turn conveys the information via nerve pulses to the brain through the optic nerve. However, the microchip does not restore perfect vision. Most cases make out only light or an image, describing the motion of an object and counting discrete objects, while some cases are able to make out shapes and recognize faces.

In general, the image would lack clarity and contrast. The ability to recognize faces or read large print is thought to be possible only with 1,000 or more electrodes.

On January 17 2008, Researchers at the University of Washington created a new contact lens embedded with electronic circuits that create tiny personal displays.

According to a Times Online report, the Argus II artificial retina has been cleared for trials, and by the year 2009, the device, costing around £15,000, may be available in the market.