There is an epidemic occurring in children that is twice as common as childhood obesity. It can affect your child’s vision for a lifetime. There may be some things you can do to reduce your child’s risk. [1-3]
The epidemic is myopia, more commonly known as nearsightedness. If your child has myopia, he or she will need glasses or contact lenses for distance vision. Twenty-five percent of young adults in the United States were nearsighted in 1971. Today that number is over 40 percent, and growing at an alarming rate. 
Myopia runs in families, and genes play a role, but they do not explain the epidemic. Genes don’t change that fast. Research suggests the causes include not spending enough time outdoors and spending too much time doing close eye focusing, like staring a computer or smartphone. [1-3]
How Children Get Myopia
As a child grows from infancy to preschool years, the shape of the eyeball changes. It becomes more elongated, like an egg. Myopia is caused by the eye becoming too long. This causes images that pass through the lens of the eye to be focused just in front of the retina at the back of the eye, where images are sent to the brain. A myopic eye is great for near vision but fails at distance vision. [1-3]
Myopic changes can occur as early as age 6. Researchers believe that there are three possible causes for this epidemic. One is that lack of exposure to natural sunlight. Sunlight may be an important trigger for proper eye growth. Another is not using distance vision enough at a young age. These two causes explain why spending time outdoors is important. Finally, too much close-focused vision favors elongation of the eye at a young age. [1-3]
Here are some research findings that support these causes:
- Children with normal vision spend an average of 4 hours more per week outdoors than children with myopia. 
- Progression of myopia in children occurs 3 to 4 times faster during the winter in the northeast, when children spend more time inside. 
- In Australia, where school children average about 4 hours of outdoor play per day, the myopia rate is less than 10 percent. In Singapore, where children only average about 30 minutes of outdoor play, the myopia rate is close to 60 percent. 
- Children who spend the most time reading, writing, and playing computer games have higher rates of myopia. In rural parts of the world where there is less access to education, reading materials, and computers, myopia rates are only at 2 to 5 percent. 
- In South Korea and some other areas of Southeast Asia, where emphasis on education and time in school is highest, 80 to 90 percent of young adults have now become myopic. [1,3]
What Can You Do to Protect Your Child?
When I go out to a restaurant with my children and grandchildren, who range in age from 3 to 8, my children will often give a smartphone to their kids to keep them occupied and quiet while we eat and talk. I have asked them to stop.
If your child is home on a nice day playing computer games, send your child outside to play. Encourage your child to be outdoors in natural light, playing and developing distance vision for a few hours each day. According to the research we have now, this is the best way to reduce the risk of myopia. [1-3]
You might think myopia is just an optical inconvenience, but it is much more than that. People with myopia are at higher risk for macular degeneration, glaucoma, and cataracts later in life. They have a ten times higher risk of retinal detachment. Wearing gasses at an early age can be traumatic for young children and the expense of glasses or contacts over a lifetime is very significant. Just try pricing a pair of prescription glasses. [1-3]
Although glasses or contact lenses can stop the progression of myopia in a child, they can not reverse it, so early intervention is key.  The American Academy of Ophthalmology guidelines say that every child should have a vision exam by a doctor or vision specialist (optometrist) at between ages 3 and 4.
Let your child’s doctor know if you notice your child squinting, or straining for distance vision, moving closer to the TV, or complaining of headaches. These could be warning signs of myopia. 
- EyeNet Magazine, Myopia Research: From the Margins to the Mainstream.
- UC Berkeley School of Optometry, Myopia: Coming Epidemic.
- National Eye Institute, Facts About Myopia, https://nei.nih.gov/health/errors/myopia
- American Academy of Ophthalmology, Eye Screening for children.