Tackle Myopia By Getting Children Out-Of-Doors, Studies Say
Spending more time outdoors may help prevent or minimize nearsightedness in children, scientists say.
AsianScientist (May 6, 2013) - Spending more time outdoors may help prevent or minimize nearsightedness in children, according to two new studies published in the journal Ophthalmology.
One study found that Taiwanese schoolchildren required to play outdoors during recess had a reduced risk of nearsightedness, and a separate study carried out in Danish children is the first to report a direct correlation between seasonal fluctuations in daylight, eye growth, and nearsightedness progression.
Nearsightedness, also called myopia, has reached epidemic levels in Asia and other regions, particularly in developed countries. Preventing or postponing the onset of this eye disorder in children may have the greatest public health impact - evidence suggests that myopia progresses faster when it develops at a younger age, leading to high myopia and an increased risk of severe eye diseases in adulthood. Although myopia is often inherited, researchers are also interested in identifying environmental factors that may help to explain the rapid rise of the disorder in some countries.
In one of the new studies, led by Dr. Pei-Chang Wu of Kaohsiung Chang Gung Memorial Hospital in Taiwan, more than 300 students from a Taiwanese elementary school were required to spend recess outdoors for a year. Classroom lights were switched off, and students were encouraged to participate in outdoor activities. The children, many of whom had previously spent recess indoors, now spent 80 minutes outdoors every day. A similar school nearby which did not require outdoor recess served as the control group.
A year later, eye exams showed that significantly fewer children in the intervention school had become nearsighted or had shifted toward nearsightedness, compared with the control school. Increased outdoor time, however, did not slow down myopia progression in children who were already nearsighted.
The study authors recommend that elementary schools add frequent recess breaks and other outdoor activities to their daily schedules to safeguard children's eye development and vision.
"Because children spend a lot of time in school, a school-based intervention is a direct and practical way to tackle the increasing prevalence of myopia," said Dr. Wu. "As an added benefit, outdoor activities may also help target childhood obesity, another epidemic of the developed world.
A separate study, led by Dr. Dongmei Cui of Sun Yat-sen University in China, investigated the impact of daylight exposure on eye development in 235 Danish school children with myopia. The participants, who were enrolled as part of a 2005 clinical trial, were divided into seven groups according to the number of hours of daylight each had been exposed to in the previous six months.
Daylight hours fluctuate markedly with the seasons in Denmark, ranging from seven hours in winter to nearly 18 in summer, resulting in distinct access to daylight for each group.
As an indicator of myopia progression, the researchers measured axial eye length – the distance from the front to the back of the eye – at the beginning and end of the six month period.
Eye elongation, or increased axial length, indicates that a person’s myopia is worsening. In children with access to the fewest hours of daylight, eye growth averaged 0.19 mm, while in those with access to the most daylight, eye growth was just 0.12 mm.
The complete picture of how daylight exposure protects against myopia is still unclear. Brighter light may help by causing pupil constriction, which lessens visual blurring, or by stimulating the production of dopamine, an eye growth inhibitor that prevents elongation, from the retina.
"Our results indicate that exposure to daylight helps protect children from myopia," said Dr. Cui. "This means that parents and others who manage children's time should encourage them to spend time outdoors daily. When that's impractical due to weather or other factors, use of daylight-spectrum indoor lights should be considered as a way to minimize myopia."
The articles can be found at:
Wu et al. (2013) Outdoor activity during class recess reduces myopia onset and progression in school children.
Cui et al. (2013) Effect of day length on eye growth, myopia progression, and change of corneal power in myopic children.
Source: American Academy of Ophthalmology.
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