Reading and writing may play more of a part than we thought in the onset of short-sightedness. How can you manage the risk?
Being short-sighted, or myopic, runs in families – so much so that genetics was thought to outweigh environmental factors. But last week German researchers put more weight on the latter, saying that the longer people stay in education, the higher the risk of short-sightedness. In the study in Ophthalmology of 4,658 people aged between 35 and 74 years of age, half of those who were university graduates were myopic, compared with 34% of non-graduates. Short-sightedness usually starts in childhood and teenage years and is increasing worldwide. In some parts of Asia, up to 80-90% of school leavers need glasses. The increase has been so rapid that genetic changes can't be solely to blame.
A study in Birmingham in 2011 found that 9.4% of children between the ages of six and seven and nearly 30% of those between 12 and 14 years of age were short-sighted. While glasses may be cooler these days, short-sightedness still isn't desirable. It carries risks in later years of conditions that can cause blindness. So can you reduce the likelihood of your child becoming short-sighted – other than by discouraging them from university?
Short-sightedness may be caused by the eyeball developing a slightly longer shape than usual. Light is then focused in front of the retina instead of precisely on to it, making distant objects look blurry. Children who are short-sighted often complain of headaches, and may squint and blink and hold books right up to their eyes.
Visual stress is thought to contribute to short-sightedness – hence the link between educational level and what researchers call "near work" (reading and writing). Studies over the past 10 years consistently show one thing might help: getting your child to spend more time outside. An Australian review found that children who spent time outdoors had a clearly reduced risk of short-sightedness.
This protective effect reduced the influence of lots of near work or having short-sighted parents – so it wasn't just that children spent less time on near work. Ultraviolet light may encourage the pupils in the eyes to constrict and increase the depth of focus and reduce blurring, or it may increase dopamine release, which may reduce lengthening of the eyeball. It does not seem to matter what children do outdoors – a picnic may be as good as a game of football. The amount of time is also unclear, although a review from the University of Cambridge found that an increase of an hour a week outdoors was associated with a 2% reduction in the odds of developing short-sightedness. Their review found that children with myopia spent 3.7 fewer hours per week outside compared with those not affected. Meanwhile, a study in Taiwan found benefits to spending 80 minutes a day outdoors. So, encouraging your children to be outdoors has something else to recommend it.
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