Might night-lights blight sight?

For now, shut off the lights in the nursery.

That's the advice of researchers who are puzzling over a study in which they find that babies exposed to light at night grew up to have much more myopia, or nearsightedness, than did babies who slept in the dark.

Of 172 children whose parents reported putting them to bed in the dark as infants, only 10 percent showed nearsightedness when examined between ages 2 and 16 at a Philadelphia clinic. Of 232 children who had slept with a night-light until they were at least 2 years old, the number jumped to 34 percent. Moreover, 55 percent of 75 babies who slept in full room light were nearsighted later.

Earlier studies in chicks also found a link between nightlights and extra growth of the eye, which causes myopia, says study coauthor Maureen G. Maguire, a biostatistician at the University of Pennsylvania School of Medicine in Philadelphia.

She notes that the new data, reported in the May 13 NATURE, suggest an association but not necessarily a causal relationship between lights and nearsightedness. Other studies have linked myopia to heredity and "near work," such as reading.

"There's definitely a genetic component, and there seems to be an environmental component," Maguire says. The researchers are again contacting parents of some of the children to look for hereditary factors that may have biased the study.