Dr. Mark Humayun of the University of Southern California, spoke at a Director's Colloquium Tuesday in the Physics Building Auditorium at Technical Area 3. Behind him is an image of eyeball that has electrodes inserted into it. According to Humayun, the electrodes prove that a patient, even though blind, is capable of seeing flashes of light. Photo by LeRoy N. Sanchez, Public Affairs

Researchers give blind patients hope for sight

After 15 years, Dr. Mark Humayun of the University of Southern California has accomplished something thought possible only in the sci-fi genre. He and his colleague, Eugene de Juan, have implanted the first microelectronic devices into eyes of blind human patients.

The retinal implant prosthesis, which takes the place of damaged retinal cells, may eventually restore vision to people suffering from diseases that cause blindness, said Humayun.

Humayun, who spoke at a Director's Colloquium Tuesday in the Physics Building Auditorium at Technical Area 3, showed illustrations of what a prosthetic device looks like. His model is a pair of sunglasses with a tiny camera hidden behind one of the lenses. The unit contains a 9-volt battery and uses modified cochlear implant technology. The sunglasses, he said, hide the fact that the patient is using a prosthesis. "People want to blend in," he said.

Cochlear implants are used to restore hearing to the deaf by stimulating neurons inside the ear. Humayun's prosthesis stimulates neurons inside the eye. A retina inside an eyeball is a composite of millions of neurons. More than 100 million light-sensing cells (photoreceptors) are present in a healthy eye.

Humayun said one of the advantages of their approach is to be able to use the ability of the human brain to adapt to a rather crude image. In other words, even with as few as thousands of electrodes, a blind person might be able to read large print. Similar adaptation of the brain allows deaf patients to understand speech without lip reading with as few as six electrodes, whereas normally there are 30,000 auditory nerve fibers.

Humayun said he and his staff, in conjunction with Department of Energy national laboratories and private company Second Sight LLC are developing future higher resolution implants. Eventually, later versions of the device may help a patient see color and spatial distribution. He showed footage of a subject learning to see with the device. The subject could see light and recognize some objects such as letters, he explained.

Two hundred thousand people go blind every year because of macular degeneration, he said.

The next scheduled Director's Colloquium is 1:10 p.m., June 24 by Eugene Johnson, professor of neurology and molecular biology and pharmacology at Washington University Medical School in St. Louis.

-- Michael Carlson

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