Our eyes are window to the world and is one of the most important of the five sensory organs namely sight, smell, taste, touch, and hearing. But we have among ourselves many less fortunate people who have physical inability to see the world around them. The inability rendered them helpless, and dependent on others. Most visually impaired people have inability to see either from the birth, or due to old age or due to any disease or accident. For all such people there is a hope in Bionic Eye – An artificial retina that can restore vision for people suffering from partial or total blindness. The device consists of glasses fitted with visual processing unit and camera able to send signals to the wireless receiver implanted in eye.

Retina in our eyes has light detecting cells called photoreceptors which convert light energy into electrical signal transmitted to the brain. In some blindness causes due to age related macular degeneration or retinitis pigmentosa light detecting cells die but other nerve cells remain undisturbed. These nerve cells cannot detect light but can respond to electrical signals. It makes the basis for Bionic Eyes.

The concept of bionic eye bypasses the natural visual display and makes use of camera pixels to the stimulating electrode array positioned on the eye. These electrodes stimulate nerve cells which can then receive input from dead photoreceptors via these arrays of electrodes. Thus nerve cells interpret the signals in the same way as they were doing for photoreceptors. This information is sent to the brain which relates the incoming electrical signals that replicates those experienced via the normally functioning eye.

The research challenge is to understand how the retina responds to electrical signals so researches are focused on how nerve cells and photoreceptors respond to light. The development of bionic eyes involves possessing of electrical properties of the retina. In fact, there are at least two silicon microchip devices that are being developed: ARGUS II and ASR. The concept for both devices is similar, with each being small enough to be implanted in the eye, supplied with a continuous source of power and biocompatible with the surrounding eye tissue

ARGUS II has a miniature camera mounted in eyeglasses that captures images and wirelessly sends the information to a microprocessor (worn on a belt) which converts the data into electronic signal and transmits it to a receiver on eye. The receiver sends the signals through a tiny, thin cable to the microelectrode array, stimulating it to emit pulses. The pulses travel to the optic nerve and, ultimately, to the brain, which perceives patterns of light and dark spots corresponding to the electrodes stimulated. Similarly the other device Artificial Silicon Retina (ASR) is an extremely tiny device with a diameter of just 2 mm (.078 inch) and is thinner than a human hair. The work is going on to have 1,000 electrodes on the retinal implant, which could allow for facial-recognition capabilities and to recognize color images.

Some applications of Bionic Eye are as follows:-

The prime application of the bionic eye is Virtual Cortex Simulation which means restoring vision for those who are partial or complete blind. Other application in the same field is Vision Ability Enhancement. There are some other applications of bionic eyes as well like for example viewing subatomic collisions.

By Aarti Bansal, Asociate Prof. ECE, Chitkara University, Punjab