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Two groups of researchers have found no association between nighttime light exposure during sleep in the first two years of life and the subsequent development of nearsightedness, or myopia. These findings appear in the March 9, 2000 issue of Nature.
The researchers, working independently and with separate data, found no link between nighttime nursery lighting and the development of myopia. Both Dr. Jane Gwiazda, director of the Children's Vision Laboratory at the New England College of Optometry, and Dr. Karla Zadnik, Glenn A. Fry Professor of Optometry and Physiological Optics at the Ohio State University, reported similar percentages of myopia in children who had slept with and without nighttime lighting before age two.
A previous study, reported in the May 13, 1999 issue of Nature, other researchers reported an association between nighttime ambient light exposure during sleep in the first two years of life and the subsequent development of nearsightedness. Using data collected by questionnaire, Dr. Richard Stone of the University of Pennsylvania Medical Center and Dr. Graham Quinn of the Children's Hospital of Philadelphia reported the strongest association with use of ambient room lighting and a somewhat weaker association with use of a night light. The findings built on earlier work by Dr. Stone and others suggesting that increased light exposure in animals early in life may play a role in the development of myopia-like conditions.
Drs. Gwiazda and Zadnik noted that myopic parents were more likely to use night lighting in their children's rooms than non-myopic parents, and suggested that failure to take this into account may have affected the results of the earlier study.
The three observational studies and their findings have been briefly summarized in letters to the editor. A full evaluation of the studies and their conclusions must await publication of more detailed reports. Differences in the results from the studies point out the importance of replicating the findings from observational studies before reaching conclusions about causal associations.
"Identifying the causes of myopia is a high research priority of the National Eye Institute because myopia affects up to 25 percent of the US adult population," said Carl Kupfer, MD, director of the National Eye Institute (NEI), one of the Federal government's National Institutes of Health and the agency that funded the later two studies. "Drs. Stone, Quinn, and colleagues have generated a hypothesis about a possible risk factor for myopia. However, in independent studies, Drs. Gwiazda and Zadnik have found no evidence that room lighting during sleep in infancy affects the development of myopia. Additional data in support of the hypothesis are needed before we can conclude that the use of nighttime lighting during infancy affects the development of myopia."