Why don't traditional corrective lenses slow myopia's progression much? Earl Smith, dean of the college of optometry at the University of Houston, has developed a theory. Glasses and contact lenses affect the image in the center of the eye. They do not address vision at the periphery. And, he said, "the peripheral retina — because there's so much more of it — can actually dominate the way that the eye grows."
Smith believes a process called "visual feedback" is contributing to the worsening of myopia in individuals who develop nearsightedness. When a person's eye is improperly focused in the peripheral region, the eye sends signals that tell it to grow. These signals contribute to the abnormal elongation of the eye. (Not all researchers completely agree: Christine Wildsoet, an expert in nearsightedness at UC Berkeley, said it's too simplistic to blame myopia only on focusing problems in the periphery.)
Based on Smith's concept, a handful of researchers and vision companies around the world are developing glasses and contact lenses that aim to eliminate signals in the periphery that may cause the eyeball to grow, and to provide visual cues that are thought to slow or stop growth.
In clinical trials, these spectacle glasses and contact lenses have been shown to slow the rate of myopic progression by 30% to 35% in children of nearsighted parents. Though prototypes of these eyeglasses have been released in Asia, Australia and New Zealand, Food and Drug Administration approval and introduction in the United States is still several years away.
"What I hope and expect is that new optical designs that improve peripheral focus will dramatically slow myopic progression," said Thomas Aller, an optometrist based in San Bruno. The earlier these treatments are started, he added, the better the results will be.
Amanda Leigh Mascarelli