-
![]()
-
![]()
closer to reality.
Researchers have investigated the use of electricity to stimulate vision for
nearly half a century. In the 1960's, a *physiologist implanted 80 electrodes on
the surface of a blind person's *visual cortex, a region at the back of the brain.
Wireless stimulation of the electrodes made the patient see spots of light known
as *phosphenes. This is the first stop for visual signals coming from the eye.
(D)
By the 1980's, a crop of *ophthalmologists began considering a narrower
and seemingly easier-to-solve problem: making *prostheses for the eye. They
suggested that degrade *photoreceptor cells called *rods and cones, still leave
large portions of the retina intact even after a patient has become totally blind.
The way to stimulate the remaining functional cells was proved *feasible in the
mid-1990's.
A device consisting of a tiny video camera perched on the bridge of a pair of
glasses, a belt-worn video processing unit, and an electronic box, was developed
recently. The electronic box issues signals to an implant behind the patient's ear
that has wires running to a grid of 16 electrodes affixed to the output layer of the
retina. The video processor wirelessly transmits a simplified picture of what the
camera images to the box, and then the retinal implant stimulates cells in a
pattern roughly reflecting that information.
