Go Play Outside: It’s Good for Your Eyes!


Go Play Outside: It’s Good for Your Eyes!
Healthy Living - February 17, 2015
William Sturrock, MD

If you are really nearsighted, you probably didn’t need reading glasses to see the recent study this past month in the journal ‘Ophthalmology’ describing twice the rates of myopia (the correct scientific term for nearsightedness) among students in wealthier, urban areas of China compared with adjoining poorer and more rural areas. In fact in Shanghai, 86% of high school students now need corrective lenses for distance sight. Previous studies have shown the correlation of myopia and such factors as intelligence, school performance, income, and inheritance -- I guess like all stereotypes, there is a kernel of truth in the popular depiction of the nerdy bookworm having thick glasses. But researchers are now focusing on (pardon the pun!) finding the causal mechanisms behind these observed correlations.

A previous study from Australia in 2008 compared ethnic Chinese students living in Singapore with those in Sydney. What they found was a ten fold increase in myopia, from 3% of those living in Sydney going up to 30% of the same aged kids in Singapore, but it did not correlate with hours spent studying which had been the earlier hypothesis. Instead the real difference between the two groups were the hours spent outside, with the Sydney kids engaged in significantly more outdoor play than their Singapore counterparts. They speculated that the frequent change in the focal distances that outdoor activity requires was a good thing for the developing eye.

Now there is an even more exciting theory for these observed differences between children that get outdoors and those that live primarily indoors. Researchers have discovered that sunlight stimulates the release of dopamine from the retina, and speculate that this may have a protective effect on the eye, preventing the elongation of the lens-to-retina distance which characterizes the oval shaped myopic eyeball. In addition we already know that dopamine has positive effects on mood and enjoyment when released in the brain. Who knew that science could show that Mom was right when she said it was good for us to go outside and play in the sunshine!

Of course, we know that too much of a good thing can be a problem, and that sunlight on exposed skin can cause cancer. However, if we are careful with the use of sunblock and clothing such as hats and long sleeves when outside, then we have better odds of not developing severe myopia as well as avoiding seasonal depression! The American Academy of Pediatrics and the National Assn of Sports and Physical Education have incorporated some of this science into their guidelines for outdoor play, recommending at least an hour of unstructured physical playtime, ideally outdoors, if conditions permit, every day. Three states (Alaska, Delaware, and Massachusetts) require between 20 and 30 minutes of physical playtime for every 3 hours of childcare. In addition to encouraging fitness and preventing obesity, perhaps we can avoid the next generation all needing the same coke-bottle glasses that I wore in Junior High! 

Summary of current recommendations for outdoor play: 

1. All children will benefit from at least one hour of unstructured physical play every day 

2. Weather conditions permitting, try to get this outdoors with appropriate usage of sunblock or protective clothing to prevent excess exposure to the skin, particularly between the hours of 10 AM and 4 PM in the summer. 

3. Limit the use of screen-time (TV, computers, electronic games, etc) to no more than 60 minutes for children aged 2-5, and no more than two hours for school-aged kids. 

4. Encourage schools and other child-care facilities to maintain supervised recess, preferably outdoors, for at least 30 minutes for every 3 hours of structured time.