More Time Outdoors Is Good For The Eyes
All of the technology around us today may make kids faster at configuring a new smartphone or coding a robot, but is all of that screen time affecting their eyes?
While we all know that kids should do less up-close viewing and sit farther from the television etc., recent studies have found that another factor may be at play: outdoor light (or the lack thereof).
According to one study, more time spent outdoors had a protective effect and reduced the chances that a child would go on to need myopic refractive correction in the future.
What causes nearsightedness?
Myopia, or nearsightedness, is a condition in which you can’t see far away but can see up close. It usually starts during the early primary school years. Because kids don’t know how other kids see, they often think their blurry vision is normal, so regular eye examinations are important during childhood. Really important - I didn't discover I was shortsighted until I was 9 and my parents wondered why the soccer ball kept hitting me in the face.
With myopia, the eye is growing, but growing too long for distant rays of light to focus accurately on the back of the eye. A blurry image results.
For children, eyeglasses or contact lenses move the focus back to the retina, and a clear image is formed. The too-long eye measured from front to back cannot be “shrunk,” so refractive correction is then a lifelong necessity. In adulthood, surgery is an option.
Myopia is on the rise.
A worldwide epidemic of nearsightedness has been reported. Besides creating the need to wear eyeglasses or contact lenses or to seek a surgical remedy, myopia can also result in blinding eye diseases late in life, like retinal detachment or degeneration.
Risk factors include having myopic parents but the debate about the influence of reading and other close work has flourished for more than a century.
In fact, close work such as reading, sewing, television and now computers and smartphones was always assumed to be the culprit for the increase in nearsighted kids. And it makes sense - the eye in childhood is naturally growing longer, even in normally sighted children so in a child developing myopia, the eye grows to focus on the frequently observed, near-viewing field.
However, the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study, funded by the National Eye Institute has studied this question for over 20 years in 4,979 children in order to put near-work, computer use and watching television in their proper place – essential for study and recreation but not an important factor in whether a child will need glasses.
Impressive differences for prevention.
The study found that if a child has two nearsighted parents, the hereditary genetic effects increase the child’s chances of needing glasses to about 60 percent.
If time spent outdoors is low.
But, the study also found that more time outdoors (about 14 hours per week), can nearly neutralise that genetic risk, lowering the chances of needing glasses to about 20 percent, the same chance as a child with no nearsighted parents claims.
A recent survey of papers from around the world, including Australia, England and Singapore, in the last decade aligned almost perfectly with these results.
So what’s so good about being outdoors for a child without glasses? There are several theories.
One is that children may exercise more when they are out of doors and that exercise is somehow protective. Another is that more ultraviolet B radiation from the sun makes for more circulating vitamin D, which somehow prevents abnormal childhood eye growth and myopia onset. Yet another is that light itself slows abnormal myopic eye growth and that outdoors, light is simply brighter.
The dominant theory however, is that the brighter light outside stimulates a release of dopamine from specialised cells in the retina. Dopamine then initiates a molecular signalling cascade that ends with slower, normal growth of the eye, which means no myopia.
There’s clearly much more to learn, but before you send your children out to run around the block, remind them to put on sunscreen and to wear sunglasses. Even as time outdoors might prevent the development of nearsightedness, parents will want to ensure they aren’t creating other skin and eye problems from ultraviolet light exposure.