眼睛大的人更容易近视？_BEC初级作文

眼睛大的人更容易近视？

Our eyes usually reach their full size by our 20s. The ideal is that they stop growing at the right size and will have perfect vision, but if they grow too big they'll be short-sighted and if they don't grow enough they're long-sighted, and won't be able to see things close up. Some children can have eyes that are too large by the age of five, says Dr Luff.

A review published by the University of Cambridge in 2011 found that for each additional hour spent outside each week, the risk of short-sightedness was reduced by 2 per cent. The review of studies involving 10,000 children and adolescents found that short-sighted children spent on average 3.7 fewer hours per week outdoors than those with normal vision or long-sightedness.

But how could exposure to light change the shape of the eyeball? Dr Saunders suggests that natural light in the eyeball flicks a type of biological switch that prevents it from growing too large. However, artificial light is not strong enough to flick this switch.

People with small eyes tend to be long-sighted and will have difficulty seeing close objects clearly because light rays are focused behind the retina.

But this tends to be largely genetic. 'Too much outdoor light will not make your eye long-sighted,' says Mr Luff. He adds that short-sighted people seem to suffer more complications than those who are long-sighted.

'We see far more associated eye health problems in the short-sighted than the long-sighted, so it's worth doing everything you can to try and prevent it,' he explains.