What are Bionic Eyes?

An artificial eye provokes visual sensations in the brain by directly stimulating different parts of the optic nerve. There are also other experimental implants that can stimulate the ganglia cells on the retina or the visual cortex of the brain itself. There is more concentration given to the production of artificial retinas.

Here is the description of a Bionic Eye:

Many types of artificial eyes have been designed and research is still going on. There is no standard model in this case. Researchers are working out different types of concepts.

Here are a few examples:

The prototype devices are 2 millimeters across and contain some 3,500 micro photodiodes. Placed behind the retina, this collection of miniature solar cells is designed to convert natural light to electrical signals, which are then transmitted to the brain by the remaining healthy parts of the retina.

A Belgian device has a coil that wraps around the optic nerve, with only four points of electrical contact. By shifting the phase and varying the strength of the signals, the coil can stimulate different parts of the optic nerve, rather like the way the electron guns in TVs are aimed at different parts of the screen. The video signals come from an external camera and are transmitted to the implant via a radio antenna and microchip beneath the skin just behind the ear.

Implants of a microchip, smaller than the head of a pin and about half the thickness of a sheet of paper were used to remove blindness.

Engineering details of the Bionic Eye:

First, for visually impaired people to derive the greatest benefit from an enhanced-vision system, the image must be adapted to their particular blind areas and areas of poor acuity or contrast sensitivity. Then the information arriving instantaneously at the eye must be shifted around those areas. The thrust of all prosthetic vision devices is to use an electrode array to give the user perceptions of points of light (phosphenes) that are correlated with the outside world. Thus, to achieve the expected shift of the image across the stimulating electrode array, the camera capturing the image must follow the wearer's eye or pupil movements by monitoring the front of the eye under infrared (IR) illumination. The eye-position monitor controls the image camera's orientation. If the main image-acquisition camera is not mounted on the head, compensation for head movement will be needed, as well.

Finally, if a retinal prosthesis is to receive power and signal input from outside the eye via an IR beam entering the pupil, the transmitter must be aligned with the intraocular chip. The beam has two roles: it sends power, and it is pulse-or amplitude-modulated to transmit image data. Under the control of eye movement, the main imaging camera for each eye can swivel in any direction. Each of these cameras--located just outside the users' field of view to avoid blocking whatever peripheral vision they might have--captures the image of the outside world and transmits the information through an optical fiber to a signal-processing computer worn on the body.

Some facts about Bionic Eyes

Scientists at the Space Vaccum Epitaxy Centre (SVEC) based at the University of Houston, Texas, are using a new material, comprising tiny ceramic photocells that could detect incoming light and repair malfunctioning human eyes. Scientists at SVEC are conducting preliminary tests on the biocompatibility of this ceramic detector.

The artificial retinas constructed at SVEC consist of 100,000 tiny ceramic detectors, each 1/20th the size of a human hair. The assemblage is so small that surgeons can’t safely handle it. So, the arrays are attached to a polymer film one millimeter in size. After insertion into an eyeball, the polymer film will simply dissolve leaving only the array behind after a couple of weeks.