One of the most common stereotypes about the young person who is nearsighted is that he or she is reading under the covers at night, but a study conducted by optometrists at four sites across the U.S. questions whether reading is the real problem.
The research, funded by the National Eye Institute and conducted over the past 23 years suggests that children can’t read themselves into becoming nearsighted, nor does reading worsen myopia so that they need a stronger prescription.
The real reason children become nearsighted seems to be because one or both parents are nearsighted. However, it appears that, despite genetics, spending time outdoors could help prevent myopia in children.
National Eye Institute Research
Avoiding reading, the computer or other near work is not the way to maintain good eyesight or to slow the progression of myopia.
The study followed nearly 5,000 children over time to see what factors were different between those who became nearsighted and those whose eyesight stayed the same, needing no vision correction.
Investigators reported that myopic children do, in fact, fit the stereotype of engaging in more near work than others. The surprising finding was that reading and other near work didn’t cause the myopia and, once myopic, children’s near work had no effect on the rate of progression of the nearsightedness.
Genetics vs. Environmental
The study has shown that a child who spends more time outdoors lowers the probability that he or she will develop myopia and has the potential to lower the risk by quite a lot. Normal vision children with two myopic parents have the greatest genetic risk of becoming nearsighted themselves. Those who spent the least amount of time outside (5 hours or less per week) had about a 60 percent chance of becoming myopic.
However, normal vision children with two myopic parents who spent 14 hours a week or more outside reduced the probability of becoming myopic by 20 percent. Children with one or no myopic parents also benefitted from spending more time outdoors. Time spend outdoors lowers the risk of the onset of myopia but doesn’t seem to affect its progression.
Vitamin D a Factor
One effect of spending more time outdoors is greater production of vitamin D from exposure to UV light. Nearsighted children spend less time outdoors, but even adjusted for this factor, they had 20 percent lower levels of vitamin D in their blood than children with normal vision.
Increased vitamin D levels might have a favourable effect on the ocular ciliary muscle. A more flexible ciliary ring might preserve the stretch on the crystalline lens during growth and may prevent or delay the start of myopia. Vitamin D would not affect the growth of the eye directly, perhaps explaining why more time outdoors doesn’t affect the rate of development once myopia has occurred.
Sending children outside to play can have a beneficial effect, not only for the eye, but also on other risk factors in children, such as preventing obesity and diabetes.
