Myopia and night lighting. Investigations on children with negative family history.

Purpose: The aim of our study was to investigate if ambient lighting at night before the age of 2 years is associated with the occurrence of myopia in a large population of Polish children. To eliminate the influence of genetic factors, only children with a negative family history of myopia were included.

Material And Methods: A total of 3905 students, all of whom had a negative family history of myopia were examined (1800 boys and 2105 girls, aged 6-18 years, mean age 12.2, S.D. 3.3 years). The examination included retinoscopy under cycloplegia with 1% tropicamide. Myopia in the subjects was defined as a spherical equivalent of at least -0.50 dioptres. The parents of all students examined completed a questionnaire on the child's family history of myopia as well as the child's exposure to light emitted by incandescent or fluorescent lamps before the age of two years. Data analysis was performed using chi-squared Pearson test; p-values of <0.05 were considered statistically significant.

Results: Sleeping until the age of two with a room light is not associated with the presence of myopia during school years (p>0.05). No differences in the use of light emitted by incandescent or fluorescent lamps on the prevalence of myopia was found (p>0.05).

Conclusions: Myopia is not associated with night light use before age of 2 years in a population of Polish children with a negative family history of myopia. Because both, the restricted population and results differ from our previous positive associations, perhaps early light exposure and family history/genetics interact in influcencing the occurance of myopia.