Increasing the amount of time school children spend outdoors and the amount of natural light they are exposed to may be the key to tackling the growing global surge in myopia.
The condition is now a significant problem in many East Asian countries, affecting more than half of the Chinese population and as much as 70% of graduates in Singapore. At the current rate of growth, it is estimated that as many as 2.5 billion people, a third of the global population, could be affected by short-sightedness by 2020.
In a feature published in the journal Nature earlier this month, Professor Ian Morgan, from the Australian National University in Canberra, said that children may need to spend three hours each day in a brightly lit environment of 10,000 lux, whereas a typical well lit office or classroom may only receive 300–500 lux.
Highlighting the current ‘myopia boom’ experienced around the world, the article reports on results from Professor Morgan’s research. In a three-year trial in China of six and seven-year-old school children, Professor Morgan’s team was able to reduce the prevalence of myopia simply by adding on 40 minutes of extra outdoor time at the end of each school day. In Taiwan, the effect was increased further, when children received 80 minutes outside.
The researcher told Nature: “We've got proof of principle that increasing the amount of time children spend outside actually works...The question then, is how do we make this work in practice at a level that would have a significant impact?”
While the exact mechanism remains unclear, findings from other groups researching chicks are pointing to the potential role of the neurotransmitter dopamine.
During the day, levels of the neurotransmitter are boosted, providing a chemical signal for the eye to switch from rod cells to cones. The dim lighting of the classroom environment may interfere with this system, throwing the diurnal rhythm out of sync and leading to extension in axial length.
The long-term effects associated with high myopia (-6.00D) include increased risk of cataract and glaucoma. Potentially of greater concern is the potential for retinal detachment.
In an interview for the Nature podcast, Professor Morgan said: “When you get to high levels of myopia the eye becomes so enlarged that people become at risk of blindness. You could possibly see an increase [up to] four-fold in the amount of blindness in the elderly, and that would be an enormous social cost.”
Potential solutions include light boxes, which can recreate the higher intensity lighting conditions of outdoors in countries experiencing reduced daylight (such as during winter in the upper northern and southern hemisphere). As well as atropine eyedrops, spectacles and multifocal and ortho-K contact lenses.
But reorganisation of the education system may be required, as a poster campaign in Singapore advising children demonstrates: “Keep myopia away, go outside and play.”
Earlier this month researchers from the Brien Holden Vision Institute (BHVI) met with the World Health Organization as part of a joint global scientific meeting on myopia.
Professor Brien Holden, of the BHVI, said: “It is clear that environmental factors play a role in the induction of myopia and that increasing time spent outdoors may reduce or delay the onset of myopia. We recognise, however, that this is just one of the factors and it is best interests of a potentially myopic child that myopia management takes a holistic approach; using myopia control spectacles and contact lenses, good visual hygiene, limit excessive use of tablet-based near work and make sure the potentially myopic child spends` time in a relaxed 'distance' environment.”
The researcher told OT: “Our data, and data compiled from a number of studies, show that the younger the child, the faster the progression of myopia. Children who develop myopia at the age of seven are more likely to have a higher magnitude of myopia than children who develop it later, for example, 14 years old. Clinicians should target such young children and their parents for special myopia control interventions.”