Turns out, there's truth to the stereotype of the "four-eyed bookworm."
A new study in the journal Ophthalmology suggests reading and schoolwork may have a greater influence on nearsightedness (also called myopia) than genetics.
The findings are based on 4,685 people who underwent eye exams and genetic tests and answered lifestyle surveys. Researchers from the University Medical Centre Mainz in Germany found that among people who had graduated from school after 13 years (which is how long it would take to complete the most rigorous levels of German primary and secondary school), 60.3 percent were near-sighted.
Meanwhile, 41.6 percent of people who graduated after 10 years of school and 27.2 percent of people who graduated after nine years of school were near-sighted. And among those who never graduated from secondary school, 26.9 percent were near-sighted.
There were also stark differences in nearsightedness rates depending on the degree. More than half of university graduates included in the study -- 53 percent -- were near-sighted, while only 34.7 percent of high school grads had the condition. And those without any professional training at all had only a 23.9 percent rate of near-sightedness.
Researchers also looked at 45 genetic markers associated with nearsightedness, but found that education levels were a much stronger predictor of myopia.
"In the past, nearsightedness had been believed to be almost completely predetermined by genetic factors," study researcher Dr. Alireza Mirshahi wrote in an email to HuffPost. "Our study clearly shows that the relevance of genetic predetermination for developing myopia is much lower than that of environmental factors."
The people included in the study were between ages 35 and 74; Mirshahi hypothesized that another study of even younger people might yield even more dramatic results because of the relatively recent rise of screen use. "Nearwork" during the developing years is associated with higher rates and severities of near-sightedness, Mirshahi noted, so "one can speculate that the younger Internet, smartphone and tablet generations will be even more myopic [near-sighted] than the cohort we analyzed."
While nearsightedness can be easily treated with eyeglasses, contact lenses or surgery, it can also raise future risk of more serious health problems like glaucoma or retinal tears and detachment. One way to guard against myopia, or near-sightedness? Go outside, Mirshahi recommended. Switching your gaze between close and far objects can also give your eyeballs a more varied workout, instead of exercising the same muscles over and over again.
"Current studies from East Asia -- where nearsightedness is a serious health problem -- have shown that outdoor activity might be preventive for the development of myopia in children and adolescents," Mirshahi said. "Since students with a higher educational performance appear to be at a higher risk of nearsightedness, it makes sense to encourage them to spend more time outdoors as a precaution."