Implants May Help Cure Blindness
a Bionic Eye
artificial retina, which uses a microchip etched with thousands of solar
cells to gather light, could eventually help blind people see again.
T A N F O R D, Calif., Nov. 5 —
When most people think of microchips, they think of computers. But scientists
are experimenting with putting silicon chips into the human eye in place
of damaged tissue. It’s a breakthrough that may cure certain types of blindness.
restore vision by creating an electrical induced prosthesis to place into
the eye,” says pediatric ophthalmologist and inventor Dr. Alan Chow, whose
company is working on a “bionic eye.”
These implants are targeted
toward people with retinal diseases such as macular degeneration and retinitis
pigmentosa, which cause blindness and vision impairment in 10 million Americans.
More than 1 million of these people are legally blind.
a Bionic Eye
In cases where the retina fails, the nerves behind the
retina, which carry electrical impulses, still function. The damaged light
receptors of the retina interrupt the connection between the eye and brain
and cause blindness. The trick is to work around the damaged retina to
stimulate those nerves.
Chow and his brother Vincent,
an electrical engineer, decided to combine their specialties in the early
1990’s to create a microchip that could control that stimulation. Their
company, called Optobionics, is working to perfect and manufacture the
The development of “silicon
retinas” has been driven by miniaturization. Researchers have created microchips
just three millimeters across that house 4,000 to 5,000 microscopic solar
cells. When the chip is implanted into the back of the eye and light strikes
those solar cells, the light is converted into electrical signals that
travel through the optic nerve to the brain and are interpreted as an image.
In effect, these microchips
replace the eye’s malfunctioning natural sensor with an artificial sensor,
manufactured on a piece of silicon.
“With this process,” Vincent
Chow says, “the brain, when it receives a signal, should not be able to
tell the difference whether it came from a natural, healthy retina or from
The Chows have tested their chip in blind animals and
successfully produced visual sensations. To date, the chip will work in
the eye for only a limited period of time, but development continues and
tests in human eyes are anticipated within two years.
Currently their device displays
only black and white images and works best in well-lit rooms. But as researchers
are able to cram more solar cells onto each chip, sight will improve further.
And these bionic eyes may eventually
give people their sight back.
the Light—With a Little Help
around the world are exploring ways of restoring sight to people with retinal
degeneration. Some are using a source of external input that feeds into
the microchip, which could produce more sophisticated images.
One prototype, developed by scientists at several universities including
North Carolina State University and the Massachusetts Institute of Technology,
uses a small video camera-equipped device to capture images, encode them
and send them into the eye implant via a laser beam that also powers the
chip's solar cell. Photosensors convert the light and images into electrical
impulses, which charge a plate that stimulates the nerves and transmits
visual information to the brain.
The laser and camera can easily be mounted on eyeglasses without
to wear bulky headgear. Germany's Retina Implant Association is working
on a related system using a digital signal processor in place of the video
camera, along with an adaptive module to receive perception feedback from
the person and adjust the light stimulus accordingly.
As for implanted microchips, "it's too early to tell if the chip could
actually work in a human eye," says North Carolina State University professor
Dr. Wentai Liu.
Development continues to gauge the compatibility of silicon with living
tissue, and to make the microchips as noninvasive to the eye as possible.