It is often said that what the mind can conceive and believe it can achieve and mankind has certainly conceived of many things that have been highlighted,  especially in Hollywood.   From the silver screens, biotechnology has developed a bionic arm that allows amputees to control movements of their prosthetic limbs with their thoughts and a training system called BrainPort is allowing people with visual and balance disorders to bypass their damaged sensory organs and instead transmit information to their brain through the tongue.  Well, scientists have now also developed a 'bionic eye' that may hold the key to returning sight to people left blind by hereditary disease, namely, retinitis pigmentosa.

The artificial eye, called the Argus II Retinal Prosthesis System, was developed by US firm, Second Sight and a team of doctors at London's Moorfields Eye Hospital have used the technology to treat patients in the UK as part of a clinical study into the therapy.

It said the technology may be able to restore a basic level of vision by allowing patients to see large objects, but experts have said the research is still in its infancy.

The Argus II Retinal Prosthesis System takes the place of  photoreceptors (the cells at the back of the retina that perceive light patterns and pass them on to the brain in the form of nerve impulses) that have been damaged from the effects of retinitis pigmentosa and other inhereted eye diseases. 

The system consists of five main parts:

• A digital camera that's built into a pair of glasses. It captures images in real time and sends images to a microchip.
• A video-processing microchip that's built into a handheld unit. It processes images into electrical pulses representing patterns of light and dark and sends the pulses to a radio transmitter in the glasses.
• A radio transmitter that wirelessly transmits pulses to a receiver implanted above the ear or under the eye
• A radio receiver that sends pulses to the retinal implant by a hair-thin implanted wire
• A retinal implant with an array of 60 electrodes on a chip measuring 1 mm by 1 mm

The whole system is operated via a battery pack that's housed with the video processing unit. When the camera captures an image of a tree for example, the image is in the form of light and dark pixels. This image is sent to the video processor, which converts the tree-shaped pattern of pixels into a series of electrical pulses that represent "light" and "dark." The processor sends these pulses to a radio transmitter on the glasses, which then transmits the pulses in radio form to a receiver implanted underneath the patient's skin. The receiver is directly connected via a wire to the electrode array implanted at the back of the eye, and it sends the pulses down the wire.

When the pulses reach the retinal implant, they excite the electrode array. The array acts as the artificial equivalent of the retina's photoreceptors. The electrodes are stimulated in accordance with the encoded pattern of light and dark that represents the tree, as the retina's photoreceptors would be if they were working (except that the pattern wouldn't be digitally encoded). The electrical signals generated by the stimulated electrodes then travel as neural signals to the visual center of the brain by way of the normal pathways used by healthy eyes -- the optic nerves. In macular degeneration and retinitis pigmentosa, the optical neural pathways aren't damaged. The brain, in turn, interprets these signals as a tree and tells the subject, "You're seeing a tree."

It takes some training for patients to actually see a tree. They initially see mostly light and dark spots. But after some time, they learn to interpret what the brain is showing them, and they eventually perceive that pattern of light and dark as a tree.

It is expected that this system will be comercially available by 2010 if upcoming clinical trials are successful.  It is estimated to cost US$30,000.00.