Teenagers who are exposed to increased amounts of sunlight are less likely to develop myopia or nearsightedness in adulthood.
According to the study, higher exposure to ultraviolet B (UVB) between ages 14 and 29 years may have reduced odds of myopia or nearsightedness -- a condition in which close objects appear clearly, but far ones do not -- in adulthood.
For the study, the research team from the London School of Hygiene and Tropical Medicine in Britain, examined the association of myopia with UVB radiation, serum vitamin D concentrations, and vitamin D pathway genetic variants, adjusting for years in education in 371 participants with myopia and 2,797 without.
No independent associations between myopia and serum vitamin D3 concentrations or variants in genes associated with vitamin D metabolism were found, the researchers said.
In contrast, those who had the highest blood levels of lutein -- a nutrient found in leafy vegetables -- had nearly half the risk of myopia compared with those with the lowest levels.
"The association between UVB, education, and myopia remained even after respective adjustment. This suggests that the high rate of myopia associated with educational attainment is not solely mediated by lack of time outdoors," said Astrid E. Fletcher from the London School of Hygiene and Tropical Medicine.
"As the protective effect of time spent outdoors is increasingly used in clinical interventions, a greater understanding of the mechanisms and life stages at which benefit is conferred is warranted," Fletcher added.
The study is published in the journal JAMA Ophthalmology.