How does a Bionic Eye work?

For millions of Indians who suffer from loss of vision due to retina damage and age-related macular degeneration, there is now hope. A bionic eye which would help them see is going to be developed indigenously. The visual device would use eyeglasses fitted with digital cameras and a retinal implant and has been successfully tried on patients abroad. The co-inventor of the global project, Dr Rajat N Agrawal, says he wants to make the implant affordable here and will work to bring down the cost of the implant to Rs 5 lakh from its present cost of Rs 45 lakh (approx). (Times of India)

What is a Bionic Eye?

Bionic Eye, technically known as “visual prosthesis” is an experimental visual device to restore vision in those suffering from partial or total blindness. It has been successfully tried on 37 patients in Europe. The Indian scientist involved in the global project is now collaborating with experts from various IITs to produce a cheaper version in India 1 Digital cameras built into a pair of glasses convert images into electrical impulses. Images are processed through video-processing microchip and sent to a radio transmitter in the glasses 2 Radio transmitter sends pulses to receiver implanted under the eye 3 Information passed to retina implant (electrode array) that sends image to brain through optical nerve 4 Each electrode gives a perception of a spot of light. When multiple electrodes are stimulated, subject is able to sense shape and size too.

There are several projects going on for development of a Bionic eye , which is not only successfully bring the vision back but also is cost effective. One of the earliest projects is the Argus Retinal Prosthesis System, whose recent version Argus II Retinal Prosthesis System can provide sight — the detection of light — to people who have gone blind from degenerative eye diseases like macular degeneration and retinitis pigmentosa. Retinitis pigmentosa is an inherited disease that affects about 1.5 million people around the globe. Both diseases damage the eyes’ 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, where the impulse patterns are then interpreted as images. The Argus II system takes the place of these photoreceptors.

This retinal prosthesis contains 5 parts as follows:

  • 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 entire system runs on a battery. When the camera captures an image (such as a tree), the image is in the form of light and dark pixels. It sends this image 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 subject’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.”(with inputs from Times of India and