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Doctors Test Chips in Eyeballs to Restore Sight

July 20, 2001 02:03:00

CHICAGO - Illinois doctors plan to implant microscopic chips in the eyeballs of three people suffering from retinal damage, in the second phase of a study that may determine whether chips can restore human vision.

A year ago, three other people who had lost almost all of their vision to retinitis pigmentosa -- a hereditary condition in which the retina gradually degenerates -- were the first to receive implants of the microchip, smaller than the head of a pin and about half the thickness of a sheet of paper.

''We've had more than a year to follow these patients,'' ophthalmologist Alan Chow, the co-inventor of the device, told Reuters in an interview. ''Implanting three more people from the same patient group will give us a larger statistical base to evaluate these results.''

Chow said a woman and two men suffering from the degenerative condition will have the chip implanted within the next two weeks.

The 2-1/2-hour procedure will take place at Central DuPage Hospital in Winfield, Ill., where two of the patients underwent procedures last year, and at Chicago's Rush-Presbyterian St. Luke's Hospital.

Chow, citing U.S. Food and Drug Administration guidelines, declined to say whether the three original patients now enjoyed better vision.

The data must first be submitted to regulators, he said. If the FDA gives him the green light, he can talk soon about specific results.

In the present clinical trials to study the safety and feasibility of the chip, the FDA has authorized implants in up to 10 patients. The results will determine whether additional patients will be enrolled in the study.

The microsurgery starts with three incisions smaller 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.

Surgeons then make a pinpoint opening in the retina to inject fluid in order to lift a portion of the retina from the back of the eye, creating a pocket to accommodate the chip. The retina is resealed over the chip, and doctors inject air into the middle of the eye to force the retina back over the device and close the incisions.

The chip, called Artificial Silicon Retina (ASR), is manufactured by Wheaton, Ill.-based Optobionics Corp., a company founded by Chow and his brother Vincent Chow, an electrical engineer.

The chip is just 2 millimeters in diameter and 1/1000 of an inch in thickness. It requires no batteries or wires and is completely self-contained, since it is powered by the light that enters the eye.

The chip contains 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. Healthy cells convert light into electrical signals within the retina.

Loss of photoreceptor cells occurs in people with RP and other retinal diseases, including macular degeneration, a condition in which the central area of the retina degenerates.

Macular degeneration and RP are the two most common causes of untreatable blindness in developed countries, affecting at least 20 million people worldwide.

The chip cannot help people with blindness caused by severe glaucoma or diabetes.

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Date last modified August 1, 2001