Exercise and Eyesight

Tell your kids to go outside and play...it is good for their bodies, and seems to be good for their eyes as well. A recent study conducted by the Avon Longitudinal Study of Parents and Children (ALSPAC) showed children 8-9 years of age who spent either no time or less than one hour per day outside were 40% more likely to become nearsighted by the age of 15 than children who spent three hours a day or more outdoors in the summer and more than one hour daily in the winter. Could this be nature’s way of promoting healthy development?

Nearsightedness (Myopia) 101

Nearsightedness, or myopia, is a vision problem that causes objects at a distance to be blurry. A nearsighted person can clearly see objects that are close to them, but has a hard time focusing on objects that are far away. People are usually nearsighted because either their cornea is too steep or their eyeball is longer than normal causing light to come to a point of focus before hitting the retina.

Environment and Nearsightedness

Research has shown that environment plays a role in the development of nearsightedness. Experiments in animals have shown that the deprivation of clear, sharp vision can cause the eye to grow longer and become nearsighted. Other studies have proposed that the amount of light you are exposed to during the day affects vision development.

A strong negative association exists that correlates to the amount of time children spend outdoors and the development of more nearsightedness or myopia. It seems children that spend more time outdoors develop less nearsightedness than children that spend less time outdoors. Researchers are still trying to establish whether it is simply being outdoors that may cause children to develop less myopia or the fact that children who spend more time indoors are completing more intense and prolonged near work or study.

Is it that simply being in a more open environment where the eye can gaze at long distances make children develop less nearsightedness? Working on near tasks or reading for prolonged periods of time have been considered as a potential contributor to nearsighted development although this has been extremely controversial with conflicting results from different studies.

Genetics and Nearsightedness

Scientists think that the genes you inherit may not necessarily cause you to become nearsighted but can cause you to become nearsighted if exposed to certain environmental conditions such as limited light exposure or constant near stimuli. Certain genes may predispose you to become nearsighted. However, studies of twins provide fairly concrete evidence that some nearsightedness is indeed inherited and eye doctors regularly see nearsightedness develop in children whose parents are both nearsighted.

ALSPAC Study Findings

The ALSPAC study was conducted in Great Britain and included over 7000 children. Results showed that children 8-9 years of age who spent lots of time outdoors were associated with a lower incidence of nearsightedness over the study period. The study also showed that children who spent time outdoors being physically active showed some decreased incidence of developing nearsightedness.

The study's investigators felt that a definite trend exists in children who became nearsighted who were not as physically active, but admitted there may be other factors involved that could influence that.

The authors of this study also pointed out that there seemed to be less incidence in the development of nearsightedness during the summertime than in the winter. Researchers looked at the amount of physical activity that each child performed while being outdoors as opposed to just being outdoors for a certain amount of time. It appeared that children who developed nearsightedness spent 10-20% less time in sports or outdoor physical activity in the four years before nearsightedness onset and continued to spend less amounts of time after they became nearsighted.

Alternative Factors

Researchers are still not sure why being outdoors is good for children’s visual development. They asked the following:

1. Is it just being exposed to sunlight as opposed to ambient room light?
2. Is it just the amount of time spent outdoors?
3. Is it the amount of physical activity that one may perform more because they are outside?

According to the study it seems that children who spent more time outdoors had less incidence of nearsightedness. They also concluded that there may be a different relationship between physical activity and nearsightedness. It may not necessarily be that less physical activity causes more nearsightedness but rather the development of nearsightedness may cause one to be less physically active. More studies will shed some light on these relationships. However, one thing we know is true. Because there are plenty of other health benefits of exercise and playing outdoors, encouraging children to spend more time outside is a positive thing.

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1. Guggenheim, Jeremy A. Time Outdoors and Physical Activity as Predictors of Incident Myopia in Childhood: A Prospective Cohort Study. Investigative Ophthalmology and Vision Science, 2012.
2. Young, Terry L. Dissecting the genetics of human high myopia; a molecular biologic approach. Trans Am Ophthalmology Soc. 2004, pp 423-446.