Nearsightedness, or myopia, is a vision defect that occurs when the eyes are unable to focus light from distant objects correctly on the retina. A person with myopia can see objects that are near clearly, but objects that are far away are blurred.
Nearsightedness usually first appears in elementary school children, although it can develop in adults as well. Research indicates that it is an inherited trait: children whose parents are nearsighted are more likely to be too. Although the inclination to acquire myopia is probably inherited, the development of the condition can be affected by the way one uses the eyes. For example, a person who spends a lot of time reading or who does a lot of computer or other near-sighted work may be at higher risk of developing nearsightedness.
Myopia has become increasingly common over the past 50 years, and it is estimated that it now affects around 1.6 billion people worldwide, with the number expected to rise to 2.5 billion by 2020, according to the Institute of Eye Research. In the United States, nearsightedness affects nearly 30 percent of the population.
A team of Australian researchers believes the rise in nearsightedness is due to more children growing up in environments where they don’t see faraway objects and their eyes aren’t adapted to focus on distant objects as they develop. Cases of global myopia are more prevalent in societies where children watch TV and play computer games rather than play outside, they say. In cities like Hong Kong and Tokyo, 30 to 50 percent of 12-year-olds are myopic; in the United States, it is about 20 percent for this age group.
A report published in the January issue of Optometry and Vision Science found that children with myopia spent an average of 8.3 hours a week outdoors, and children without myopia spent an average of 12.6 hours outdoors. The study also found that, on average, children with nearsightedness watched several additional hours of television per week.
The researchers, from the New England College of Optometry, said sunlight could expand the range in which objects are clearly visible. The effect appeared to be similar with both active and passive outdoor activity.
Symptoms and correction of myopia
Common symptoms of nearsightedness in children include squinting to see distant objects, difficulty reading the blackboard at school, sitting close to the television, and disinterest in playing outside.
Nearsightedness doubles the risk of glaucoma and retinal detachment, both of which can lead to vision loss later in life.
A basic vision test will determine if a person is nearsighted. Nearsightedness is relatively easy to correct with contact lenses or glasses. The lens bends the images entering the eye and focuses the image correctly. Depending on the severity of myopia, wearers may only need to wear their lenses for certain activities. Adults may also consider laser surgery, which can only be done after the eyeball is fully developed.
Another option to treat nearsightedness is called orthokeratology or corneal refractive therapy. With this treatment, myopic patients wear specially designed rigid contact lenses that gradually reshape the cornea.
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