I want to put a night light in my four-year-old's bedroom, but I've heard that this may cause him to have myopia in the future. Is there any truth to this?

M.

In 1999, University of Pennsylvania researchers published a study that reported infants who sleep with night lights have a higher risk of developing nearsightedness (myopia). The study involved 479 eight-year-olds, and queried their parents about the lighting conditions in the children's bedrooms between birth and age two. Researchers found 34 percent of children who slept with a night light were myopic, compared with 10 percent of those who did not.

However, the study failed to take into consideration what is believed to be the strongest determining factor in myopia: heredity. It may be that parents who are nearsighted are more likely to use night lights to see clearly into their children's rooms than those with better vision. So, follow-up studies were performed in Boston and at Ohio State University. Both of these newer studies, published in the journal Nature, found no correlation between the use of night lights and the development of myopia. So, it is now the general consensus among doctors that it is okay for children to sleep with night lights on.