This report explores a relationship between nocturnal light exposure at ages 0 to 2 years and the later development of myopia. In a retrospective study at a University of Pennsylvania pediatric ophthalmology clinic, the authors reviewed the records of 479 children, ages 2–16 years, seen as outpatients whose parents completed a study questionnaire in 1998 (selection criteria not specified). The study group consisted of 55% males, of whom 70% were Caucasian, and 30% African-American. Children with significant ophthalmologic disorders or a history of prematurity were excluded.
The main focus of the questionnaire was the report by parents that a night light or regular room illumination was used or not used regularly at night while the child was sleeping during the first 2 years of life. The refraction of these children was measured during a clinic visit. The prevalence of myopia was strongly associated with ambient light exposure during sleep at night in the first 2 years after birth. The relation between light exposure and myopia development was deemed dose-dependent, since “a greater proportion of children” who slept with regular room lighting became myopic when compared to children who slept with only a night light or in darkness (no additional statistics presented). There was no relationship between nighttime lighting and myopia after age 2, suggesting a possible critical period for refractive development. On the basis of these findings, the authors recommend that children below the age of 2 sleep without artificial lighting at night.
A great deal of radio, newspaper and magazine attention has been paid to this study, which was published in Nature’s “Scientific correspondence” section. Unfortunately, this report reveals that it is possibly fatally flawed.
While any recommendation must await the performance of controlled, more detailed prospective studies, concerned parents might consider substituting subdued night lights for full room illumination.