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An epidemic of myopia, or short-sightedness, is coming to New Zealand and steps should be taken now to cope, an action group has warned.
Myopia rates in some Asian countries are estimated to be approaching 90 per cent in 20-year-olds and prevalence in some Western countries is sharply increasing as well.
A 2013 study of 17-year-olds in Sydney, for example, found myopia had reached 30 per cent, double the rate seen a little more than 10 years earlier.
There’s a surprising lack of data on New Zealand rates of near-sightedness – 4.2 per cent of Dunedin 11-year-olds in a 1984 study but little else, according to Alex Petty, a therapeutic optometrist in private practice in Tauranga, and a founding member of the New Zealand Myopia Action Group.
But there’s every reason to believe increased myopia is already hitting this country and will increase, Petty said.
‘‘In New Zealand, myopia’s risks are largely underappreciated . . . Even many health professionals are not familiar with myopia, its [consequences] or its prevention,’’ he wrote in an editorial in the December issue of New Zealand Medical Journal.
Scientific understandings of myopia have morphed over the decades. The condition clearly runs in families and, for many years, it was thought genetics were the driving factor.
But the marked increases in Asia – from about 15 per cent in the mid-1950s in Taiwan to about 85 per cent in the late 2000s, for example – cannot be explained by genetics. The human genome doesn’t move that quickly.
Thinking turned towards environmental factors, and research in the past 15 years has found time spent outdoors seems to be an important factor in preventing myopia. The opposite – time spent indoors – is associated with increased myopia.
The mechanisms are not entirely understood, said Petty.
One theory is that natural light helps by preventing elongation of the eye. In simple terms, elongation causes myopia.
Another idea is that higher dopamine levels brought about by exposure to the sun are good for the eye, Petty said.
There is also a clear association between more education, higher IQs and more myopia but, again, the mechanisms are not clear.
Some have suggested that ‘‘near work’’ – close reading of books and the like can be the cause.
Recently researchers have pushed ‘‘near work’’ to include computers and devices with screens. But it’s likely screens themselves don’t cause the problem, Petty said. It’s probably that kids and teens use their screens much more indoors than out.
Myopia is inconvenient for most people, Petty said, as they have to wear glasses or contact lenses. But the costs fall most heavily on the poor, and cost over lifetimes can be substantial.
The risk is that myopia leads to high myopia, a more severe form that can lead to retinal detachments, macular degeneration, glaucoma, cataracts, and blindness.
There are preventions – get outside, kids – but no cures for either type of myopia.
Myopia interventions include special soft contact lenses, as well as contact lenses worn at night (orthokeratology). But neither is fully funded by the Government.
There is a drug available in New Zealand called Atropine, an eye drop. It is not funded and must be physically mixed by pharmacists, increasing cost and lowering supply.
The recently founded Myopia Action Group wants to address funding problems, raise awareness and incorporate myopia into all Year 7 vision checks undertaken at schools, among other initiatives.
There’s every reason to believe increased myopia is already hitting this country and will increase.