WASHINGTON — Scientists are testing artificial retinas that they hope can restore partial sight to people who have lost their vision to the most common causes of blindness.
Retinitis pigmentosa, which ruins peripheral vision, and macular degeneration, which causes a blurred or blind spot in central vision, affect millions of people, especially the elderly.
Both diseases irreparably damage the retina, the light-sensitive patch at the back of the eye that converts images into signals and relays them to the brain.
Government-sponsored tests of a relatively crude artificial retina began on six patients in 2002. With the aid of these devices, people who had been totally blind were able to read foot-high letters, tell a plate from a cup, find doors and windows, and navigate around large objects, according to Brian Mech, vice president of Second Sight Medical Products.
This first-generation eye implant consisted of a tiny camera on a pair of dark glasses and a hip-mounted microprocessor. The bionic gadget relayed images to a silicon chip containing an array of 16 electrodes — conductors of electrical signals — that was surgically attached to the front of the retina. The electrodes created a 4-by-4 pattern of light and dark in the visual processing center at the back of the brain.
At first, patients saw only scattered bits of light. With weeks or months of retraining, however, they learned to make out straight lines, distinguish light areas from dark ones and detect motion. The training was necessary because the brain loses ability to interpret sight after disuse.
Artificial retinas are still experimental and won’t be available for commercial use for years. The devices will cost at least $30,000, Mech said. Still, scientists are optimistic about the future of artificial retinas.
