Teenagers who spend little time in sunlight have twice the risk of being short-sighted and not able to see long distance clearly, researchers say.
They say it could explain a surge in myopia, or short-sightedness, in parts of South-East Asia with big student populations who spend a lot of time indoors. One theory is that exposure to sunlight helps the retina release the chemical dopamine, which stops the eyeball from growing elongated and distorting the focus of light entering the eye.
A study of 1400 West Australians aged 20 and 21 used a new camera system that takes ultraviolet photographs to assess sun damage. While the photos showed that more exposure to sunlight meant more damage to the surface of the eye, it also meant people were less likely to be short-sighted.
Dr Charlotte McKnight, clinical lecturer with the Lions Eyes Institute at the University of WA, said the findings suggested young people had to strike the right balance regarding sun exposure.
Dr McKnight said the study was unable to prove little outdoor activity caused myopia.
She was not suggesting people spend a lot more time outside, which could increase skin cancer risks and eye diseases such as pterygium.