But as he showed a reporter last week, that's enough to let him find a mannequin in a room, walk to a black stocking cap hanging on a white wall, and then return to the mannequin to plop the cap on its head.
He can also recognize a 2-inch-tall letter from five feet away, said researcher William Dobelle.
The man's performance is the first demonstration that an artificial eye can provide useful vision, said Dobelle, who's developing the device.
"He can do remarkably well" with the limited visual signal, Dobelle said.
Dobelle is chairman of the Dobelle Institute, a medical device company in New York. He described the device and its performance in this month's issue of the ASAIO Journal, a publication of the American Society of Artificial Internal Organs.
Richard Normann, who studies artificial vision at the University of Utah, said he's encouraged by how much the blind man can do. The new report suggests that someday, even limited signals to the brain will let blind people do relatively complicated visual tasks, he said.
It's the first demonstration of useful artificial vision, he said, but he stressed the device is still "a very limited navigational aid, and it's a far cry from the visual experience that normal people enjoy."
Dr. Bill Heetderks, who directs a National Institutes of Health program to develop electronic implants that work with the brain, said an implant that helps blind people navigate would be a major step forward.
"When Dr. Dobelle provides additional details on his methodology that establishes this result, we may be there," Heetderks said after reading Dobelle's report.
While Dobelle's device uses a brain implant, some other scientists are studying implants in the retina. The retina strategy made news recently when blind entertainer Stevie Wonder expressed interest.
Dobelle's patient, who asked to be identified only as Jerry, has been blind since age 36. Now 62, he volunteered for the study and got the brain implant in 1978; scientists have been working since then to improve the software.
To use the device, Jerry wears sunglasses with the tiny pinhole camera mounted on one lens and an ultrasonic range finder on the other. 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 small 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 the specks of light. The shifting patterns as Jerry scans across a scene tells him where light areas meet dark ones, letting him fin the black cap on the white lab wall, for example.
The device provides a sort of tunnel vision. At any one time, it can cover an area about the size of a card 2 inches wide and 8 inches tall, held at arm's length.
Jerry uses the device only two or three days a week at Dobelle's lab, as researchers tinker with it. One question is how best to provide depth perception, using signals from the range finder. Jerry had to walk cautiously as he approached the mannequin and the wall during the lab demonstration, with an arm out to prevent collisions.
Dobelle said an improved version of the device should go on sale overseas in limited quantities this year. It's not clear when it might become available in the United States, he said.
Written By Malcolm Ritter