Why homework can harm your child’s eyesight
COUlD sending your child to a good school and making sure they do their homework be putting their eyesight in serious danger? That’s the concern raised by research that reveals alarmingly strong links between time spent studying hard and childhood short-sightedness — myopia — that can lead to serious eye diseases.
Myopia causes distant objects to appear blurred, while close ones can be seen clearly. It often develops in childhood, with the eyeball starting to elongate, becoming more egg- shaped t han spherical, or the lens becoming too curved, so the light entering the eye is not focused correctly.
It used to be thought that myopia was largely genetic, but a sharp increase in the number of children affected suggests there may be environmental factors at play, too.
Short- sightedness among British children has doubled over the past 50 years. Now a study published by the Population Health Research Institute at St George’s University of london has found that children at highly academic schools (which have a selection test) were more than two-and-a-half times more likely to develop myopia than those who went t o non- selective, l ess academic institutions.
The study, published in the journal Investigative Ophthalmology & Visual Science, involved 660 children aged 12 and 13 living in Northern Ireland.
‘ It looks as if schoolwork — which requires near-eyesight work — might be a strong risk factor for myopia in children,’ one of the researchers, Dr Christopher Owen, an epidemiologist, told Good Health.
‘Children who are being pushed academically may be at more risk of myopia than those who are not.’
HE SAYS the study findings echo results from other r esearch. For instance, in east Asia, where children are often academically hothoused from an early age, the rise in myopia is even greater.
Sixty years ago, 10 to 20 per cent of the Chinese population was short-sighted. Today, up to 90 per cent of teenagers have myopia, according to the journal Nature.
Scientists disagree about what is behind the link between the time spent in class and shortsightedness. Some suggest that lack of natural daylight is the primary cause (the theory is that light triggers the release of brain chemicals important for healthy eye growth).
But others believe that the main culprit is an excess of close-up eye work caused by study.
Perhaps the main problem, Dr Owen suggests, is that children’s developing eyes ‘get used’ to short-sightedness when they do a lot of screen and book work for s c hool , because t hey are constantly having to focus on something close to them.
‘Being myopic means always having your eyes on a near point of focus,’ says Dr Owen.
‘Myopia may develop because you get used to looking at things close up. Studies on chicks and mice have shown that when they are kept in an environment where they can only see things close up, they develop myopia.
‘This is all quite speculative and needs teasing out. It might also be that genes are somehow involved — for example, that there may be a susceptibility to myopia in some people’s genes that nearsight work might make worse.’
The problem with myopia isn’t just about needing glasses — being short-sighted may sentence millions of young people to serious eye conditions later in life.
This is the warning from Ian Flitcroft, a consultant paediatric ophthalmologist at the Children’s University Hospital in Dublin.
He s ays t hat while many opticians regard myopia as something that causes short-sightedness and no other consequences, a review of research he published in the journal Progress in Retinal and eye Research found that it significantly increases the risk of sight-threatening problems.
These include glaucoma — where fluid pressure builds up inside the eyeball, causing gradual loss of vision — and retinal detachment, where the retina ( the l i ghtsensitive patch at the back of the eye) peels away.
Without rapid treatment, the retina may detach, leading to vision loss and blindness.
It’s not fully understood why myopia increases t he risk of t hese conditions, but the risk is significant, according to Mr Flitcroft. He warns that the risk of glaucoma developing from childhood myopia is about the same as the risk of getting heart disease from smoking.
The key to protecting your child may be as simple as ensuring they play outside as much as possible in the school holidays and after school.
Research published in 2012 by Cambridge University ophthalmologist Justin Sherwin, which reviewed 23 studies on myopia in children and adolescents, concluded that spending time outdoors may help protect against myopia. A previous study, in 2008, suggested playing outside can make up for lots of time spent doing close-up academic work.
For two years, researchers at Sydney University followed up on more than 4,000 children aged six or 12 — children who did a lot of close-up academic work and spent most of their time indoors were more likely to become short-sighted.
Significantly, the study also found that children who were in the top third f or spending ti me on close - up academic work had no increase in myopia risk if they were also in the top third for spending time outdoors. It didn’t matter what the children were doing outdoors.
The recent study by St George’s University of pupils at academic schools showed similar results — the children who spent more than average time playing outside, about half their waking day, were significantly less likely to have myopia than those staying indoors.
Chinese school designers are busy building on these ideas in an attempt to tackle their country’s rising myopia rate. In Guangdong province, for example, they have constructed bright-light classrooms with walls and ceilings made of see-through plastic.
Two years ago, Taiwanese researchers got one school to l ock i ts students out of the classroom during break-time and lunch. As a result, students had 80 minutes more sunlight during the school day.
Fewer children became near-sighted compared with those from another school that didn’t follow the policy.
Yet Mr Flitcroft says sunlight itself might not be the only factor. Being out in open spaces may present developing eyes with large three- dimensional vistas that provide a variety of focusing experiences which teach their eyes to focus properly.
ARTIFICIAL 3D imagery is different, however, and using 3D glasses — for example, at the cinema — may undermine their sight.
The journal, Optometry Today, reported in 2011 that children need a clear, sharp and stable image in each eye in order for their vision to develop properly.
With 3D, two images of the same thing shown f rom a slightly dif f erent angle are vi ewed through special lenses; the brain then puts these images together to create 3D.
The thinking is that this may harm that development and cause problems with focusing in young eyes.
last year, the French government’s health watchdog, the Agency for Food, environmental and Occupational Health and Safety, re c ommended t hat children under six should not be allowed access to 3D content.
It added that children up to the age of 13 should only use the technology ‘moderately’.
One word of caution about sending your children out into the open summer sun, though. As well as suncream to protect their skin, they need proper sunglasses.
Young eyes are especially vulnerable to the sun’s rays because the developing l ens i s very clear, meaning more UV light filters into the eye.
The long-term risk is damage such as cataracts (where the lens becomes cloudy) and age-related macular degeneration (loss of vision i n the part of the eye responsible for central vision).
Sunglasses should carry a Ce mark (a european standard of UV protection). They also need to be a good, snug fit, so that light doesn’t simply come in through the sides and the top.
Whatever the exact physical causes of childhood myopia may be, the message for protecting against it is clear.
Get the children off the sofa, give them a cool pair of sunnies and let them play out in the open. Their eyes will thank you for it.