A new Canadian study shows that children who spend less time outdoors are more likely to suffer from myopia.

With children becoming more and more glued to their tablets, televisions and cell phones, their eyesight is becoming worse.

A new Canadian study shows that an increase in nearsightedness in children is largely due to the fact that kids are spending less time playing outdoors and more time looking at a screen.

According to a Science News for Students, one in three people in the United States has nearsightedness—or myopia.

According to the new study led by Mike Yang of Canada’s Centre for Contact Lens Research in Waterloo, Ontario, the risk a child will develop myopia decreases by approximately 14 percent with just one additional hour of outdoor time per week.

Yang worked with researchers at the Canadian National Institute for the Blind in Toronto in examining the eyes of 166 students from first to eighth grade in Waterloo during the 2014-2015 school year.

According to the results, just 6 percent of first graders suffered from myopia. However, by age 13, the percentage with myopia rose to 29 percent.

After examining the students, the researchers then surveyed the parents about their child’s activities, including how much time the child spends outside, which was a big predicative factor on whether or not the child became nearsighted.

The study also found that almost one in every three children with myopia was undiagnosed and never prescribed glasses to correct the condition.

According to Yang, the untreated condition could impact how a student learns in school as they often cannot see the blackboard, which can slow their learning.

However, Jeremy Guggenheim, an optometrist who has studied myopia in Great Britain and Hong Kong, said children who wear glasses avoid outdoor sports out of fear of damaging or losing their glasses.

Previous research has suggested that myopia may stem from children spending too much time focusing on close-up objects including books, phones and video screens. Another study has linked the rising rates of myopia to a decrease in time children spend outdoors. Previous research also concludes that children are becoming myopic at much younger ages.