Dutch children have an increased risk of becoming short-sighted because they spend more time on computer screens and less time playing outdoors, ophthalmic professor Caroline Klaver says in Wednesday’s NRC.

Half of the people in Europe in their 20s wear glasses or have contact lenses, Klaver says. And people who have glasses of -6 or more at a young age have a one in three risk of developing serious sight problems or even going blind, she told the paper.

Myopia develops when the eyeball grows too long, relative to the focusing power of the cornea and lens of the eye.

Klaver says short-sightedness is the biggest cause of blindness and that spending long times indoors reading or behind a screen increases the risk.

‘We have to ensure that far fewer children develop short-sightedness by making sure they are outside for two hours a day,’ she said. ‘That exposes them to a substance [dopamine] which brakes the growth.’ Schools in particular should ensure children have an hour outdoors.

Research by the Erasmus medical centre in Rotterdam shows that 2.4% of six-year-olds are short sighted. They were also more likely to have a shortage of vitamin D, to be overweight and not to play outside.