Myopia has long been linked to spending too much time inside, but new research suggests that just simulating the outdoors in classrooms could help ward off the condition in children.
Short-sightedness, or myopia, generally emerges as the eye changes shape during normal development in early life, and the distance between the cornea at the front of the eye and the retina at the back becomes too long. This results in blurry vision of distant objects because light coming from them is being focused in front of the retina, rather than on it.
Myopia is becoming more common, especially among children. We aren’t sure why this is, but spending can cut the risk. The main hypothesis is that this enables exposure to , but is that the outside world offers more visual stimulation with scenes containing “high spatial frequencies”. This means that there are sudden changes in visual stimuli, such as edges as opposed to mainly smooth, monotonous features, and the thinking is this stimulation may protect against myopia.
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To investigate this idea, at Central South University in China and his colleagues created an indoor environment with many high spatial frequencies by decorating a classroom to look like a woodland. This involved covering walls and even desks with images of trees and bushes and making the ceiling resemble the sky.
Lighting was slightly adjusted in the classrooms to make it consistent between the two groups. “As the walls are less reflective when covered with tree images etc., lights were adjusted so that illuminance on the desks was the same in the two classrooms,” says team member at Children’s Health Ireland at Temple Street Hospital, Dublin.
For one year, Lan’s team had about 250 children, aged around 9, from 10 classes at a school in Lijiang in Yunnan province take their lessons in a classroom decorated like a woodland, while another group of around 250 children learned in a traditional-looking classroom, painted white.
Before and after the study, the children were assessed for signs of myopia, according to the curvature of their eye lenses. This is measured in dioptres, with the generally defined as -0.50 dioptres.
After one year, the eyes of long-sighted children in the outdoor-mimicking classroom, those who struggle to focus on things very close to them, had moved towards myopia 0.22 dioptres less than those in the traditional classroom. For children with 20/20 vision, their eye curvature changed 0.18 dioptres less.
“I think it’s clinically significant,” says at the University of Georgia in the US. “If you can’t prevent kids from getting myopia, at least you can reduce the degree of myopia.”
However, if the students already had myopia, the woodland classrooms made no difference. They probably couldn’t see the high spatial frequencies as well as the other children, so it would have had little effect for them, says Hammond.
The findings seem to support the idea that spatial frequencies are important to myopia risk. The eye grows according to the stimuli it sees, says Hammond. Environments with artificial light that lack high spatial frequencies may result in limited eye development, he says, whereas the outdoors provides a huge range of patterns and changes of colour, distance and brightness, encouraging a workout for the eyes.
Outdoor scenes could be implemented cost-effectively in classrooms and other indoor environments, says Lan. “According to the students, the design did not distract their attention; instead, they felt it enhanced their study efficiency.”
“The study is a nice first indication,” says at Johns Hopkins University in Maryland. “But I’d want a lot more information before anyone makes a recommendation that everybody should try painting outdoor scenes on the walls of classrooms.” Spending more time outdoors is probably preferable to reduce a child’s myopia risk, and for the other benefits it brings, says Frick.
Hammond echoes this point. “Painting the walls with murals is not even close to the experience of going outside, but it’s probably better than nothing,” he says.
medRxiv
