A retinal implant is a biomedical technology which is currently under development by a wide number of private companies and medical research institutions throughout the world. The aim of the implant is to partially restore some useful vision to those who have lost their sight due to degenerative eye conditions such as macular degeneration and retinitis pigmentosa.
Whilst other forms of blindness result from cataracts and diseases of the optic nerve or brain, retina diseases like macular degeneration only involve the rods and cones in the eye, leaving the cells connecting the brain to the eye intact.
In many ways the implant system mirrors the use of a cochlear implant to restore hearing to deaf patients. The implant currently being designed will rest on the inside surface of the retina, opposite to the damaged rods and cones. In this position the implant is in contact with the relay cells to the brain. Current designs for the implant contain two silicone chips located within a silicone capsule.
The top chip receives light entering the eye from a very small laser attached to a pair of glasses. The glasses will also contain a small CCD (charge-coupled device) camera which will convert the visual scene into a series of laser pulses that will carry power and visual signals into the eye.
The second chip will then decode the visual information from the laser in a similar way to how a TV decodes an airwave signal. This visual signal will then be sent to an electrode relay which in turn transmits electric pulses into the nerve cells of the eye.
One of the main issues facing designers is the problem of powering the implant. Unless the implant is able to power itself then surgery to replace batteries or a permanently attached wire would be necessary. It’s thought that this will be solved by using a very small solar panel which can provide more than enough power to run the implant independently.