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New Device May Help People Blinded by Certain Conditions

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By Elizabeth Tracey , MS
WebMD Health News

March 6, 2000 (Baltimore) -- In November 1999, Stevie Wonder told the congregation at a Detroit church that an implantable computer chip might help him to see for the first time in his life. Intense media attention was then focused on Johns Hopkins researchers, who are developing and testing a device called a retinal chip. "We think we will have an implant for use in humans in about five years," says Gislin Dagnelie, PhD, assistant professor of ophthalmology at Hopkins and one of the researchers on the project.

Unfortunately for Mr. Wonder, the retinal chip is limited to use in people who are blinded due to diseases such as retinitis pigmentosa, in which a patient's visual field gets progressively smaller, and macular degeneration.

Dagnelie tells WebMD, "This technology is really only appropriate for persons who have had sight at some time, because it depends upon correct interpretation of the visual signal by the brain." He says it also requires that the portion of the brain that processes visual information be functioning." Wonder lost his vision shortly after birth.

The retinal chip is a very small array of electrodes that would be implanted in a person's eye. The chip converts visual information coming in through the pupil to signals that are then transmitted to other cells in the eye, and from there to the brain. The result would be a pattern in shades of white, black, and gray. Initial tests using a version of this chip have demonstrated that patients can recognize simple patterns or follow a light.

"The electrodes we want to use now are actually a bit different," says Dagnelie. "They are under development by a California company, which is filing the investigational device approval with the FDA. Once they are approved, we will use them in a strain of Irish setter dogs, which develop a condition quite similar to retinitis pigmentosa but with a much quicker time course. It's gratifying to think that the work we do with these animals will actually improve their lives."

In separate research, the National Institutes of Health (NIH) is working to use a different part of the brain to enable patients to have enough vision to get around more easily. William Heetderks, MD, NIH program director for neural prostheses at NIH, says, "Visual prostheses have the potential to be quite practical and to vastly improve life for a large number of people."

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