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- CHICAGO (Reuters) - Illinois
scientists on Friday said they have successfully implanted silicon microchips
beneath human retinas for the first time, a procedure that holds promise
for millions of people with failing eyesight.
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- Earlier this week, three patients who lost almost all
of their vision from retinitis pigmentosa -- a hereditary condition in
which the retina gradually degenerates -- became the first people to have
an Artificial Silicon Retina implanted.
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- Doctors said they will not know for weeks whether the
chip has restored vision because the incisions made to implant the device
must first heal.
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- The patients are wearing shields over their eyes to protect
from light and debris.
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- The 2-1/2-hour operations, performed at the University
of Illinois at Chicago Medical Center and at Central DuPage Hospital in
Winfield, Illinois, were part of a Food and Drug Administration-approved
study to determine whether the chip can be tolerated.
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- Doctors said initial signs suggest the chip -- smaller
than the head of a pin and about half the thickness of a piece of paper
-- had not been rejected.
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- Cautious Optimism
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- ``We'll have to wait three or four weeks to see how it's
functioning,'' Dr. Alan Chow, the ophthalmologist who invented the device
with his brother, Vincent Chow, an electrical engineer. ``We're cautiously
optimistic.''
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- The chip contains about 3,500 microscopic solar cells
that convert light into electrical impulses. It works by replacing damaged
photoreceptors, the so-called light-sensing cells of the eye. Those cells
normally convert light into electrical signals within the retina.
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- Loss of photoreceptors cells occurs in people with retinitis
pigmentosa and other retinal diseases including macular degeneration, a
condition in which the central area of the retina degenerates.
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- Macular degeneration and retinitis pigmentosa, the two
most common causes of untreatable blindness in developed countries, affect
at least 30 million people in the world.
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- The chip will not help people with blindness caused by
severe glaucoma or diabetes.
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- The implants require no batteries or wires. They are
completely self-contained since they are powered by light that enters the
eye.
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- Doctors hope the implants will stimulate the retina so
patients develop some vision.
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- ``We still don't know how much vision can be restored.
It's still very early,'' said Alan Chow, president and chief executive
of Wheaton, Ill.-based Optobionics Corp., which developed the chip.
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- He said he ``tossed and turned'' for six hours the night
before the first surgery worrying about what might go wrong.
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- ``The thing that surprised us most was how smoothly it
went,'' he said.
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- Surgery Detailed
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- The microsurgery starts with three tiny incisions no
larger than the diameter of a needle in the white part of the eye. Through
the incisions, surgeons introduce a vacuuming device that removes the gel
in the middle of the eye and replaces it with saline solution.
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- Surgeons then make a pinpoint opening in the retina to
inject fluid in order to lift up a portion of the retina from the back
of the eye, creating a pocket to accommodate the chip.
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- The retina is resealed over the chip. Doctors then inject
air into the middle of the eye to force the retina back over the device
and close the incisions. The air bubble is reabsorbed and replaced by fluids
created within the eye within a day or two.
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