Scientists have been working since 1978 to develop and improve the software
that enables Jerry to use the device as a primitive visual system. Jerry’s “eye”
consists of a tiny television camera and an ultrasonic distance sensor mounted
on a pair of eyeglasses. Both devices communicate with a small computer,
carried on his hip, which highlights the edges between light and dark areas in the
camera image. It then tells an adjacent computer to send appropriate signals to
an array of 68 small platinum electrodes on the surface of Jerry's brain, through
wires entering his skull behind his right ear. The electrodes stimulate certain
brain cells, making Jerry perceive dots of light, which are known as phosphenes.
Jerry gets white phosphenes on a black background. With small numbers of
phosphenes you have (the equivalent of) a time and temperature sign at a bank.
As you get larger and larger numbers of phosphenes, you go up to having a
sports stadium scoreboard.
If he is walking down a hall, the doorway appears as a white frame on a dark
background. Jerry demonstrated by walking across a room to pull a woolly hat off
a wall where it had been taped, took a few steps to a mannequin and correctly
put the hat on its head. A reproduction of what Jerry sees showed crosses on a
video screen that changed from black to white when the edge of an object
passed behind them on the screen. Jerry can read two-inch tall letters at a
distance of five feet. And he can use a computer, thanks to some input from his
8-year-old son, Marty. "When an object passes by the television camera ... I see
dots of light. Or when I pass by it," Jerry says. The system works by detecting the
edges of objects or letters. Jerry, currently the only user of the latest system,
must move his head slightly to scan what he is looking at. He has the equivalent
of 20/400 vision - about the same as a severely nearsighted person - in a narrow
field. Although the relatively small electrode array produces tunnel vision, the
patient is also able to navigate in unfamiliar environments including the New York
City subway system.