Artificial Retina Implant in Phase II
March 26, 2008
Clinical trials have begun on a
second-generation artificial retina implant.
California -- The FDA has recently approved new
clinical trials to test the latest artificial retina
implant model -- the Argus II.
Researchers at the Doheny Eye Institute at the
University of Southern California Medical Center
have begun enrolling study patients with
retinitis pigmentosa (RP) -- a blinding retinal
disease. The Argus I artificial retina model has
already undergone human implant tests that indicated
the safety and long-term reliability of the
implants. During the Argus I's testing phase, six
RP patients received the retina prosthesis.
Each of these previously blind patients have been
able to distinguish and identify objects and motion.
The new, smaller Argus II is believed to be safer
and more effective.
How it works
Vision begins when light enters the eye through
the
cornea, moves through the
lens and
vitreous and
strikes the
retina, the inner-most lining of the
eyeball. The retina, a light-sensitive layer of tissue,
sends visual messages through the
optic nerve to the
brain, where the visual impulses are interpreted as
an image. Retinal diseases like,
age-related macular degeneration and
retinitis pigmentosa decrease vision by
destroying the light-sensitive photoreceptor cells
in the retina.
With the artificial retina device, a miniature
camera mounted in eyeglasses captures images and
wirelessly sends the information to a microprocessor
(worn on a belt) that converts the data to an
electronic signal and transmits it to a receiver on
the eye. The receiver sends the signals through a
tiny cable to the microelectrode array,
stimulating it to emit pulses.
The artificial retina device thus bypasses
defunct photoreceptor cells and transmits electrical
signals directly to the retina’s remaining viable
cells. The pulses travel to the optic nerve and,
ultimately, to the brain, which perceives patterns
of light and dark spots corresponding to the
electrodes stimulated. Patients learn to interpret
these visual patterns.
Clinical trials on a third model are projected to
begin in 2011.
It is important to note that, as of the March
'08, all artificial retina devices are still
experimental and are not yet commercially available.
*Dr. Deupree and The Macula Center do not
perform artificial retina implants.
M.E.
Some information provided by U.S. Dept. of Energy:
ArtificialRetina.energy.gov
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