And now with two studies to the contrary, it's safe to say parents can leave the lights on. The two follow-up studies were done separately at the New England College of Optometry and Ohio State University. The original study was done by scientists at the University of Pennsylvania and the Children's Hospital of Philadelphia and was published in Nature last May. It raised the possibility that too much light during the first two years of life prompts the rapidly developing eyes to grow excessively and throws them out of focus. The follow-up studies found no difference between the rate of myopia for children who slept in the dark and those who slept with a night light.
Myopic parents are more likely to have myopic children.
And myopic parents may like to leave night lights on so they can see better at night. The Boston group studied 213 people ranging in age from 2 to 24, with a mean age of 11. It found that 20 percent of the children who slept with night lights developed myopia, exactly the same percentage as the youngsters who slept in the dark. The Ohio State study, which involved 1,220 children with a median age of 10, found the percentage of children who became nearsighted after sleeping with a night light as babies was about 17 percent. Statistically, that was the same as the 20 percent of the children who slept in the dark.