Could more outdoor activity reduce the risk of shortsightedness? Katie Williams says that it could.
Myopia, or short-sightedness, is the commonest eye condition worldwide and results in blurred distance vision. This can be corrected with glasses or laser refractive surgery, but the individual continues to be at a higher risk of sight-threatening complications such as retinal detachment.
There has been a sharp increase in the prevalence of myopia over recent years, most dramatically in Southeast Asia. In parts of Taiwan and Singapore 80-90 per cent of young adults are myopic. The prevalence in the UK is not as high, around 30 per cent, but there is recent evidence of rising prevalence here also. This raises concerns for the future.
Myopia typically develops in late childhood and adolescence with progression in early adulthood. A number of strong risk factors for myopia have been identified including urbanised environments, education, reading and intelligence. These factors are most influential in childhood.
Encouragingly children who spend more time outdoors are less likely to develop myopia. A meta-analysis of seven child and adolescent studies concluded a two per cent reduced odds of myopia for every additional hour spent outdoors a week. Interestingly this finding has been replicated in very variable climates including Europe, the US, Singapore and Australia.
It is not entirely clear what element of time spent outdoors is protective. Initial studies helped to clarify that time outdoors is beneficial independent of taking part in outdoor sports or the degree of physical exertion. It appears that light intensity, ultraviolet radiation, distant focus and vitamin D, produced in the skin after light exposure, may all play a role.
Suggesting children spend more time outside is a very attractive therapeutic option. It is cheap, safe and has other health benefits such as the potential to reduce childhood obesity. Interventional studies to test the efficacy of spending more time outdoors as a means to reduce the future number of children developing myopia are currently underway in parts of Southeast Asia. These include enforcing break periods outside, structured weekend outdoor activities and pedometers to encourage increased walking.
- Dr Katie Williams is Clinical Research Fellow at the Department of Ophthalmology, King’s College London (firstname.lastname@example.org)
- Rose KA et al. Outdoor activity reduces the prevalence of myopia in children. Ophthalmology 2008;115(8):1279-85.
- Sherwin JC et al. The association between time spent outdoors and myopia in children and adolescents Ophthalmology 2012;119(10):2141-51.
- Guggenheim JA et al. Time outdoors and physical activity as predictors of incident myopia in childhood. Invest Ophthalmol Vis Sci 2012;53(6):2856-65.
AuthorDr Katie Williams Clinical Research Fellow at the Department of Ophthalmology, King’s College London
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