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Back To Vidyya The Eyes Have It

New Implant May Help Many Regain Sight

The first artificial "eye" device to tap directly into the optic nerve is due to be implanted into a blind woman sometime within the next four months. If the device works as hypothesized, it could one day restore at least a modicum of vision to many blind people, including those with damaged or destroyed retinas.

The "eye", developed at the Catholic University of Louvain in Belgium, provokes visual sensations in the brain by stimulating different parts of the optic nerve. Other experimental implants stimulate the ganglia cells on the retina or the visual cortex of the brain itself. But the Louvain team says these techniques require large numbers of electrodes to create recognisable imagery, making them difficult to build.

The new Belgian "eye" has a coil that wraps around the optic nerve, with only four points of electrical contact. By shifting the phase and varying the strength of the signals, the coil can stimulate different parts of the optic nerve, much in the same way the electron guns in TVs are aimed at different parts of the screen. The video signals come from an external camera and are transmitted to the implant via a radio antenna and microchip beneath the skin just behind the ear.

The Belgian researchers have spent the past two years experimenting with a volunteer who has the electrode implanted, with wires leading out of her body to the signal processor. By asking her to point in response to various stimuli, researchers have been able to map camera pixels onto the corresponding parts of her visual field. This was possible, says Veraart, because the subject was once sighted and knows what it means to "look at" something.

The researchers hope the device will at least allow blind people to avoid obstacles, though more tests are necessary before the device is implanted. Most critical is the time it takes to realise that an object is looming large. It it takes the patient more than a few seconds to react to an object, then the device will be of little use to anyone. If the test patient is able to learn to react quickly then three more patients will be implanted, starting in August.

Scientists at the Royal National Institute for the Blind in London are wary of raising people's hopes prematurely. It should be noted that it is four months to the first testing phase, not four months to public availability.

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Editor: Susan K. Boyer, RN
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