Implants in brain let blindman 'see'

Scientists have enabled a totally blind man to "see" with the aid of computers and a tiny video camera attached to a set of electrodes in his brain.

Scientists have enabled a totally blind man to "see" with the aid of computers and a tiny video camera attached to a set of electrodes in his brain.

The 62-year-old man was able to see well enough to find his way around a city's underground system, read two-inch tall letters and even watch television and surf the Internet.

Although he cannot see in the conventional sense, the blind man can determine the outline of nearby objects using a visual system said to be similar to seeing stars in the sky.

"If he is walking down a hall, the doorway appears as a white frame on a dark background," said William Dobelle, who led the research team from the Dobelle Institute and the Columbia-Presbyterian Medical Centre in New York.

The blind man, called Jerry, lost his sight after a blow to his head when he was 36. He has taken part in Dr Dobelle's research programme ever since he had 68 platinum electrodes implanted in his brain in 1978.

"Each electrode on the surface of the brain produces dots of light, when stimulated, that resemble stars in the sky," Dr Dobelle said. The dots - known as phosphenes - are generated by signals from a miniature camera and a range-finder mounted onto a pair of spectacles worn by Jerry.

The signals are processed by a computer on Jerry's belt which is programmed to remove background "noise" and detect the outlines of objects.

Jerry, whose surname was not given, has demonstrated his skills at navigation by walking across a room, pulling a hat off a wall and putting it correctly on the head of a tailor's dummy. "When an object passes by the television camera ... I see dots of light," Jerry said.

Dr Dobelle, who published the research in the journal of the American Society of Artificial Internal Organs, said that Jerry's sight is limited to a narrow field of view equivalent to 20/400 vision, that of a person who is very near-sighted.

"Although the relatively small electrode array produces tunnel vision, the patient is able to navigate unfamiliar environments, including the New York City subway system," Dr Dobelle said. "By replacing the sub-miniature television camera with an electronic interface, the patient learns to 'watch' television, use a computer, and access the Internet," he said.

One of the more remarkable achievements of the research has been to introduce the wires from the electrodes through the skin of the patient without causing discomfort or infection in more than 20 years that they have been used.

The electrical impulses sent from the device's computer stimulate the visual cortex region of the brain which creates the sensation of dots of light.

A second patient who underwent an electrode transplant at the same time as Jerry was unable to see anything, perhaps because the 60-year-old went blind at the age of five and has "forgotten" how to use his visual cortex, Dr Dobelle said.

Other scientists warned that the development does not amount to a blindness cure. Richard Norman, who studies artificial vision at the University of Utah, said the system is "a very limited navigational aid, a far cry from the visual experience that normal people enjoy".

Dr Dobelle said the next stage of the research is to integrate the signals from the range finder and video camera more precisely, to give blind people some depth of vision to judge distances better.