The more years of schooling you have, the higher your risk for nearsightedness.
Observational studies have suggested a link between education and myopia. But a new study used a genetic technique called Mendelian randomization to minimize the effect of several variables and provide stronger evidence of cause and effect.
Using eye examinations and questionnaires on education level, researchers used publicly available genetic data on 67,798 men and women in England, Scotland and Wales. They examined the many specific genetic variants linked to myopia and to the genetic predisposition to time spent in school, including higher I.Q. and other factors.
The researchers found that although genetic predisposition was a more powerful predictor of nearsightedness, years of education were strongly and causally linked to the condition. They acknowledge that the people in their database were generally healthier than the general population, which could lead to bias. The report is in BMJ.
The lead author, Dr. Denize Atan, a consultant senior lecturer in ophthalmology at the University of Bristol, said the mechanism is unknown but may have something to do with reduced exposure to natural daylight.
“Clues from other studies suggest that children who spend more time outside are protected from the onset and progression of myopia,” she said. “One recent study found that just 11 hours a week of daylight exposure seemed to be enough to slow onset and progression.”