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Night-light may lead to nearsightedness

baby's room
Keeping the lights on at bedtime might help baby to sleep but might lead to nearsightedness  
Night-Light nearsightedness
CNN's Pat Etheridge talks with an opthamologist
Windows Media 28K 80K
 Exposure to light before age 2  Percent nearsighted between age 2 and 16
Slept in darkness 10 percent
Night-light in bedroom 34 percent
Room light in bedroom 55 percent
eye exam
In a study, the odds for nearsightedness increased 30 percent for children who slept with a night-light on  

May 13, 1999
Web posted at: 11:38 a.m. EDT (1538 GMT)

(CNN) -- Young children who sleep with a light on may have a substantially higher risk of developing nearsightedness as they get older, says a new study in the journal Nature.

The collaborative study of 479 children by researchers at the University of Pennsylvania Medical Center and The Children's Hospital of Philadelphia found 55 percent of children who slept with a room light on before age 2 had myopia, or nearsightedness, between ages 2 and 16.

Of the children who slept with a night-light before age 2, 34 percent were myopic, while just 10 percent of children who slept in darkness were nearsighted.

The survey was a clinical extension of results from basic laboratory research in chicks demonstrating that the relative proportions of light and dark during the 24-hour day greatly affected eye growth and refractive development.

Even low levels of light can penetrate the eyelids during sleep, keeping the eyes working when they should be at rest. Taking precautions during infancy, when eyes are developing at a rapid pace, may ward off vision trouble later in life.

"The study does not establish that nighttime lighting during early childhood is a direct cause of myopia, and there are undoubtedly other risk factors," the study's senior author, Dr. Richard Stone, said in a statement. "Still, it would seem advisable for infants and young children to sleep at night without artificial lighting in the bedroom until further research can evaluate all the implications of our results."

Besides its immediate implications, the study offers a novel explanation for the increasing prevalence of myopia over the past two centuries, as populations shifted from agricultural to urban environments. The current findings suggest that the greater ambient nighttime light levels associated with industrialization may be a factor in the high incidence of myopia in developed nations.

In the United States, at least 25 percent of the population is nearsighted.

Severe nearsightedness can increase the risk of glaucoma, retinal detachment and macular degeneration in old age.

Several eye specialists dismissed the study as premature and incomplete. They said controlled experiments would be more reliable than a retrospective questionnaire, and the study should have accounted for heredity and for outside light sources such as streetlights.

Parenting Correspondent Pat Etheridge contributed to this report.

University of Pennsylvania Health System
Children's Hospital of Philadelphia
Mayo Clinic: Is sitting close to the TV bad for a child's eyes?
National Eye Institute
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