National Geographic : 1992 Nov
THEEYEFUNCTIONS like a camera to focus light rays on the retina. The rays are bent first by the cornea, the thin transparent tissue cov ering the iris, the diaphragm that gives the eye its distinctive blue, brown, or other color. The iris expands or contracts to regulate the amount of light transmitted through the round aperture at its center, the pupil. Then the rays are bent further by a protein rich crystalline lens behind the iris; this com pletes the focusing task. Unfortunately for a hundred million Ameri cans-who have to wear glasses or contact lenses-nature gets it wrong a significant amount of the time. If the light rays are not bent enough to focus on the retina, you are farsighted. If the rays are bent too much, you are nearsighted, or myopic, a much more com mon condition. A focal point even a millimeter in front of the retina results in significant myo pia, the plight of at least a quarter of the human race, including 70 million Americans. Though scientists have long known that myopia is often associated with persons of high income, education, IQ, and status, they do not know its cause. A five-year study, sponsored by the National Eye Institute, employs sophis ticated measuring devices to track eye devel opment among schoolchildren in Orinda, California, and may yield clues, says Anthony J. Adams, dean of the School of Optometry at the University of California at Berkeley. "This is the first study to measure every opti cal component of the eye and track it over a period of time," he explains. Though conclusions about the cause of myo pia are years away, surgical deliverance is at hand, according to Russia's Svyatoslav Fyo dorov, perhaps the world's leading exponent of an operation to correct myopia called radial keratotomy. In this procedure a surgeon makes tiny spokelike incisions deep in the cornea, which flattens a bit and focuses light rays more cor rectly on the retina. "I guarantee beautiful sight," Fyodorov told me at the Eye Microsurgery Institute, his clinic on the northern edge of Moscow. "Four to 12 incisions. After 48 hours, some tears, then beautiful. For 99 percent of patients, I can guarantee 20/20." But his crusade, joined by many U. S. prac titioners, has produced skeptics as well as believers. In 1980 the National Advisory Eye Council declared radial keratotomy an "ex perimental" procedure and expressed "grave concern" until careful research validates its safety and effectiveness. The National Eye Institute commissioned a study that (Continued on page 23) Meeting Manhattan head on, Sher man puts his Seeing Eye training to the test as he guides his partner, 35-year-old Jeff Wiegers. "When I'm with Sherman, I don't feel like I'm blind," says Jeff, diagnosed with retinitis pigmentosa as a child.