Blindness risk as myopia heads towards epidemic levels
An epidemic is sweeping many Asian countries and touching on Australia’s shores – but it is not being spread by infectious means or borne by a vector such as a mosquito. Rather, the myopia, or short-sightedness, that is now affecting nine out of 10 teenagers in some Asian cities is largely the result of cultural and behavioural factors.
The most striking increases in the condition are seen in cultures where parents place a strong emphasis on education and academic achievement and where, as a result, children spend long hours studying at the expense of playing outside.
In urban areas of Singapore, China, Taiwan, Hong Kong, Japan and South Korea, about 80 to 90 per cent of school leavers now have myopia, meaning their distance vision is blurred without glasses, according to the non-profit research organisation Brien Holden Vision Institute.
In South Korea’s capital, Seoul, an incredible 96.5 per cent of 19-year-old males are myopic.
In the United States, the rate has also increased from 25 per cent of adults in the early 1970s to 42 per cent in 2004. And Australia is not immune to the problem: the institute estimates myopia levels here have doubled in the past 15 years to 31 per cent of the population.
Half the world’s population – nearly five billion people – will be myopic by 2050 if behavioural interventions and optical treatments are not developed and implemented, according to the institute’s modelling.
Most concerning is its warning that up to one-fifth of those – one billion people – will be in the high myopia category that puts them at a significantly increased risk of blindness.
The institute recently issued a plea to the world – including governments, health agencies, civil society, parents and schools – to take steps to meet this “major public health challenge of our time”.
“Firstly, the public must be made aware that this threat exists,” says Professor Kovin Naidoo, the acting CEO at the Sydney-based institute. “Secondly, we need researcher and public health practitioners to develop effective solutions. Thirdly, eye-care professionals need to be better equipped to manage patients at risk.”
Two of Australia’s leading researchers in the field are convinced that the most effective solution is as simple as stepping outside.
Spending more time outside in sunlight can protect children against developing myopia, according to Professor Ian Morgan, a retired biological scientist and visiting fellow at Australian National University, Canberra, and Professor Kathryn Rose, head of orthoptics at the University of Technology Sydney.
Myopia occurs when the eyeball becomes slightly elongated, usually during the growth period in childhood, so that the lens focuses light from far-away objects slightly in front of the retina, rather than directly on it. As a result, objects that are far away appear blurry.
While glasses and contact lenses can correct the vision, they don’t fix the underlying defect. In cases of severe or high myopia (classified as a measure of -5 or -6 dioptres or greater), the inner part of the eye becomes stretched and thin, increasing the risk of complications such as retinal detachment, cataracts, glaucoma and blindness.
For many years, myopia was thought to be genetic, says Rose, but the dramatic increase in the prevalence of the condition over the past few decades can’t be explained by genetics alone.
Previous research also points to too much near-work – such as studying or needlework – and higher levels of education as culprits for developing myopia.
While questions have been raised about the impact of children spending long periods staring at the screens of electronic devices, it is not thought to pose any greater risk than other near-work, as the epidemic of myopia began appearing well ahead of the computer age.
Rose says near-work is a risk factor, but a growing body of research shows that even intensive close-up work can be countered by sufficient time outdoors.
“One of the things that became more and more clear from our work and that of others is that time outdoors can mitigate the effect of near-work,” she says. “If you have somebody who does a high level of near-work and a high level of outdoor activity, they won’t become myopic. It is having that balance that is important.”
Rose was chief investigator on the Sydney Myopia Study into the eye health of 4000 children, who were then rechecked five years later to see what changes had occurred. Those who became myopic spent less time outdoors compared with those who weren’t myopic, according to the findings in the journal Ophthalmology. The study also found that children of East Asian ethnicity had a higher incidence of myopia and spent less time outdoors compared with children of European Caucasian ethnicity.
Rose says the high value that some East and South Asian cultures place on their children’s academic achievement is thought to be behind the difference.
Australia is generally faring better than its Asian neighbours because of the attractive climate and the value our society places on children taking part in sports and outdoor activities, she says.
Ian Morgan says animal research suggests bright light might stimulate the release of the neurotransmitter dopamine from the retina in the eye. That might block the elongation of the eye, and thus prevent myopia.
While the biology behind myopia remains debated, he too is convinced the best approach to preventing it is to ensure children spend more time outdoors during their school day.
A recent study he co-authored showed that adding 40 minutes extra time outdoors to each school day among Chinese primary school students resulted in a 23 per cent reduction in new cases of myopia over the next three years. Another school-based trial in Taiwan in which children were locked out of their classrooms during school recesses, possibly delivering as much as 80 minutes spent outdoors per day on a school day, reported a roughly 50 per cent reduction in myopia incidence.
Morgan says some countries such as Singapore have adopted myopia prevention strategies that focus on urging parents to ensure children spend time outdoors, but uptake is slow.
“Results from a recent Chinese study showed that kids who spend time outdoors actually have higher performance academically. But it is taking a long time for that message to get through.”
He adds: “The conclusion we draw is that it [time outdoors] has to be mandatory and applied in the school day, and everyone has to do it. That is the transition that needs to be made.”
Morgan, who holds a position with Sun Yat-sen University in the Chinese city of Guangzhou, is now involved in a trial of a “glass classroom” in which Chinese children will spend time each day exposed to outdoor light. “Things like the bright classroom may be important – they will deliver not just 40 minutes of sunlight a day but perhaps a couple of hours. We are also playing with the idea of having desk lamps that would deliver outside light-type intensity off the page.”
Associate professor Padmaja Sankaridurg, program leader, myopia, at the Brien Holden Vision Institute, says the myopia epidemic is now being viewed internationally as a public health emergency.
“It is definitely on the agenda of governments and health bodies because they are starting to realise that 20 or 30 years ago cataracts were the number one cause of blindness. Now, we are seeing that myopia is the leading cause of blindness in some countries,” she says.
“We need to implement programs to try to control new myopia and the way myopia progresses.”
The institute hosted a World Health Organisation meeting in Sydney earlier this year at which key international scientists, researchers and clinical experts discussed the rapidly increasing prevalence of myopia. The resulting report is due to be released soon.
In the meantime, the institute is urging parents and teachers to act now to stem the epidemic by encouraging children to spend at least two hours each day outdoors, ensuring they don’t spend too much time on activities requiring close-up focus and ensuring they are screened for vision problems regularly.
This article was first published in the print edition of The Saturday Paper on Nov 7, 2015 as "Focus on an epidemic". Subscribe here.