The latest studies on the causes of myopia – or short-sightedness – reveal what many mums and dads have suspected for generations – sunshine really is good for our kids.
Myopia in children
Short-sightedness (myopia) is a refractive error of the eye, where distance objects are not focused clearly. Close work (e.g. reading) is not usually a problem, but glasses or contact lenses are required for clear distance vision. This is because light entering the eye is focussed in front of the retina, as the eye continues to grow.
Myopia is increasing at an alarming rate, especially in East Asia, where over 90% of school leavers need glasses for distance. Researchers have been looking into the underlying causes of short-sightedness for decades now and a picture is starting to emerge of what those causes really are.
The elusive causes of myopia
Over the years, studies have shown a link between education and myopia and researchers have drawn the conclusion that reading causes myopia. But that hasn’t stood up to scrutiny. When they looked at specific behaviour, such as hours spent on digital screens or books read per week, the link to increased myopia just wasn’t there.
But when they looked at time spent outdoors, a strong association emerged.
Latest myopia study results
In one ground-breaking study, 500 children who started out with heathy vision were tracked over 5 years. After 5 years, 20% had developed myopia and the only environmental factor that was linked to this was time spent outdoors.1
A year later, Australian researchers found much the same result. In a study of 4,000 at Sydney schools over 3 years, they found that kids who spent more time indoors were more likely to become short-sighted.2
And the reason for this? Researchers propose that brighter visible light causes dopamine release from the retina, and this slows down the growth of the eye (which leads to myopia). UVB rays also create vitamin D, which may benefit the eyes, but this theory is still being tested.
The theory stacks up when applied to the highly myopic children of East Asian schools who have intensive schooling and spend less than 1 hour outside each day. Recent controlled trials have introduced a mandated two-hour period outdoors per day for these kids and that has halved the rate of new myopia cases.
Outdoor glass classrooms allow kids to be out in all weathers, and it doesn’t have to be sunny. The light levels of even the most overcast days are still well above the range for eye health, whereas even the brightest indoor lighting cannot even approach healthy levels.
Can bookworms avoid myopia?
These studies reveal what parents have long suspected – that hours spent outdoors are good for kids. This is good news for bookworms, who had been previously considered sitting ducks for the onset of myopia. The latest studies that reading books – even for hours per day – is not the culprit, and that insufficient time outdoors is.
Genetics also plays a significant role in the development of myopia, but even kids who were genetically predisposed to myopia could cut their risk by getting outdoors.
Results showed that they were three times less likely to need glasses if they spent at least 14 hours per week outdoors (compared to kids who spent less than 5 hours per week in the open air).
3 Tips for getting your kids their sunlight quota
- Walk to school: If you live within a kilometre or two of school, ditch the car and walk. This can add 30-40 minutes per day (return trip) to your kids’ sunshine time, or about 3 hours per week.
- Get up earlier: Early to bed and early to rise… etc. Especially in winter, add a morning tennis lesson or cross country run rather than doing things in the fading evening light.
- Read outdoors: You don’t have to actually run around to get the benefit of increased daylight. Studies show that even having a picnic or reading a book outdoors has the same effect on lowering the risk of myopia as engaging active pursuits.
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Time Outdoors, Visual Activity, and Myopia Progression in Juvenile-Onset Myopes.
Jones-Jordan LA, Sinnott LT et al. Invest. Ophthalmol. Vis. Sci. 48, 3524–3532 (2007).
Outdoor activity reduces the prevalence of myopia in children.
Rose KA, Morgan IG et al. Ophthalmology. 2008 Aug;115(8):1279-85. doi: 10.1016/j.ophtha.2007.