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Microchip Implants May Help Cure Blindness
Creating a Bionic Eye

Copyright ©1998 ABC News

By Jack Smith
S 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.

“We can 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.

Anatomy of 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 device.

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 our implant.”

Tests Ongoing
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.

An artificial retina, which uses a microchip etched with thousands of solar cells to gather light, could eventually help blind people see again. (Marco Doelling/

See the Light—With a Little Help
Researchers 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 having 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.
—Jenn Griffee

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Date last modified December 6, 1998