Despite popular theories that bookworms were more likely to require glasses, a study has suggested that it is time spent indoors that has an impact on eyesight, rather than reading.
Academics at Bristol University discovered that those who regularly played outdoors when they were eight and nine were almost half as likely to be shortsighted by the age of 15 as those who did not.
The study is the first in the world to establish a direct link between poor eyesight and not spending enough time outside.
Dr Cathy Williams, colleagues at Bristol’s School of Social and Community Medicine, and Cardiff University, made their conclusions after following 14,000 youngsters who were part of the Avon Longitudinal Study of Parents and Children.
Parents of eight and nine-year-olds were asked how long their child spent outdoors on a typical day.
Children were classed as spending a “high” amount of time outdoors if they were outside for at least three hours a day in summer, or an hour or more in winter. Otherwise they were classed as spending a “low” amount of time outdoors.
They discovered that being outdoors was more important, as far as the development of myopia was concerned, than being physically active.
Sight experts are still unsure why simply being outdoors appears to protect against short-sightedness.
But Jeremy Guggenheim, a reader in optometry and vision science at Cardiff University, who contributed to the research, said there was growing evidence that daily exposure to bright light was necessary to develop and maintain good vision.
Studies indicated regular exposure to bright light stimulated levels of dopamine, a neurotransmitter, in the retina.
When chickens had higher levels dopamine in their retinas, due to being kept in brighter conditions, they were less likely to develop myopia, he said.
Between a quarter and half of young people in Britain suffer from short-sightedness.
Dr Guggenheim said that, if the bright light / dopamine theory was correct, it would suggest that myopia was to some extent a modern condition, exacerbated by our indoor lives.
He added that spending hours reading – for decades the number one culprit for myopia – did not seem to blame.
“There doesn’t seem to be much connection between the time spent on different indoor activities, such as reading, and myopia,” he said.
“The more people have tried to nail down reading as the cause, the less convincing the evidence has looked.”
Dr Williams, a consultant opthalmologist, said: “We’re still not sure why being outdoors is good for children’s eyes, but given the other health benefits that we know about we would encourage children to spend plenty of time outside, although of course parents will still need to follow advice regarding UV exposure.
“There is now a need to carry out further studies investigating how much time outside is needed to protect against short-sightedness, what age the protective effect of spending time outside is most marked and how the protective effect actually works, so that we can try and reduce the number of children who become short-sighted.”
Their study is published in the journal, Investigative Opthalmology and Visual Science.
Source: The Thelegrapf