Playing outdoors can save children’s sight
NEW RESEARCH shows that kids need to spend about three hours outside each day to prevent the onset of myopia, or short-sightedness.
“We now know that getting less than 60 minutes outdoor light exposure per day is a risk factor for myopia,” Associate Professor Scott Read, from Queensland University of Technology, said. “Children need to spend more than an hour and preferably at least two hours a day outside to help prevent myopia from developing and progressing.”
Scott is now researching the characteristics of outdoor light that make it more beneficial to sight than indoor light. “The intensity of outdoor light is much brighter than indoors,” he said. “We measure light in terms of ‘lux’. Typical indoor lighting is 300–500 lux, but outside on a winter’s day it’s about 10,000 lux. On a bright summer’s day, it can be 100,000 lux or higher.”
Scott said the theory he and his fellow researchers are now working on is that it’s this brightness of outdoor light that can be beneficial to the human eye. Another factor the study is looking at is the spectrum of outdoor light – how the difference in wavelengths may also have an impact.
“We’re not 100 per cent sure yet whether light exposure is more effective in the morning, afternoon or the middle of the day, so understanding the spectrum will help guide us,” Scott said.
A cultural shift
Scott said a cultural shift to an indoor lifestyle has contributed to growing numbers of myopia in children. “It could partly be the rise in the use of devices, but the main impact is the amount of time kids are spending indoors,” he explained.
Studies into myopia in South East Asian countries – including Singapore and Hong Kong – have shown a huge prevalence of myopia, with up to 80 per cent of teenagers in the region suffering from the disorder. “When the level of outdoor activity between Australian and Singapore was compared, there was much more time spent outside by Australian children,” Scott said. “Now we need to find out how that light actually affects the eye growth and the vascular structure at the back of the eye.
“This vascular structure – called the choroid – changes as people become more short-sighted, and it can change fairly quickly. The tissue can expand or contract, and with short-sightedness it gets thinner as you become more short-sighted. Our preliminary findings also suggest that children who have greater light exposure each day tend to show less thinning of the choroid.”