Myopia, or nearsightedness, is extraordinarily common -- affecting as much as 50% of the population of the United States. Given the large number of people who need glasses or contact lenses to correct this refractive error, one might wonder how nearsighted people managed in the hundreds of thousands of years before spectacles were invented. From what is now known about myopia, most people's vision may have been considerably better in ancient times. The basis for this assertion is the surprising finding that the growth of the eyeball is strongly influenced by focused light falling on the retina. This phenomenon was first described in 1977 by Torsten Wiesel and Elio Raviola, who studied monkeys reared with their eyelids sutured closed. This procedure, obviously enough, deprives the eye of focused retinal images. Animals growing to maturity under these conditions show a remarkable elongation of the eyeball. The effect of this deprivation is a local one, since the abnormal growth of the eye occurs in experimental animals even if the optic nerve is cut. In fact, if only a portion of the retinal surface is deprived of focused light, then only that region of the eyeball grows abnormally.

Although the mechanism of light-mediated control of eye growth is not fully understood, many believe that some aspect of modern civilization -- perhaps reading and writing -- interferes with the normal feedback control of vision on eye development, leading to abnormal elongation of the eyeball. A corollary of this hypothesis is that if children wanted to improve their vision, they might be able to do so by practicing far vision to counterbalance the near work "overload". Practically, though, most people would probably choose wearing glasses or contacts rather than the onerous daily practice that would be required. Not everyone agrees that such a remedy would be effective, however, and some investigators and drug companies are exploring the possibility of pharmacological intervention during the period of childhood when abnormal eye growth is presumed to occur.

Neuroscience, Sinaur Associates (QP355.2.N487 1997)