From the New Scientist April 29.

THIS WEEK:                                                           29 Apr
00
#10  Hitting the nerve: Latest eye implant offers hope to people with
damaged
                retinas.
The first complete artificial 'eye' that taps directly into the optic nerve
is due to be implanted into a blind woman within the next four months. The
device could one day restore some vision to many blind people, including
those whose retinas have been damaged or destroyed.  Developed at the
Catholic University of Louvain in Belgium, the artificial eye provokes
visual sensations in the brain by directly 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 (New Scientist, 7
November 1998, p 23, and 22 January 2000, p 6). But Claude Veraart of the
Louvain team says these techniques require large numbers of electrodes to
create recognisable imagery, making them extremely complicated to build.
Instead, the Belgian device 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, rather like the 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 (see Diagram).  Veraart and his
colleagues 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,
Veraart and his colleague Charles Trullemans were 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. 'If it takes her 30 seconds to recognise an obstacle it will be of
little use,' says Veraart. If she reacts quickly, the team plan to implant
at least three more patients, starting in August.  Rebecca Griffith, health
promotion officer for the Royal National Institute for the Blind, in London,
welcomes the advance but is wary of raising people's hopes prematurely.
'It's four months to the testing phase, not four months to public
avail-ability,' she says.
New Scientist
Page_10; Photograph (omitted); Illustration (omitted)
Copyright © Reed Business Information Limited


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