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Shortsightedness, or myopia, is a very common vision problem that can usually be corrected with glasses or contact lenses. Myopic individuals see things up close clearly but objects farther away are out of focus or blurry. Although the condition does not significantly affect an individual’s quality of life (provided glasses are used), what’s worrisome is the high incidence of shortsightedness among people today.

The most important factor for shortsightedness is genetics, but a new study has identified more environmental factors that might explain the steep rise in myopia around the developed world.

Playing outside seems to be the most important thing a child can do to avoid myopia later in life

According to the most recent estimates, around 90% of teenagers and young adults in China have shortsightedness. According to a recent study, shortsightedness among Chinese schoolchildren rose by more than 50 percent between grade one and seven.

Genes play a major role in whether or not a person will develop the condition. However, the astonishing rate with which myopia is affecting school children around the world is much too steep to be explained by heredity alone — genes just don’t change that fast.

It follows that environmental factors are at play, and a new study published in the British Journal of Ophthalmology has both confirmed some established factors and also uncovered new ones.

The researchers at King’s College London used data from the UK-based Twins Early Development Study, which involved 1,991 twins recruited at birth between the years 1994 and 1996. Each individual’s development, behavior, education, and genetics were tracked, allowing the researchers to trace associations between myopia and the participants’ environment. 

According to the results, every extra hour a child spent on computer games each week increased the chance of them having myopia by 3%. This can be explained by the close proximity to screens and time spent indoors as sunlight exposure is critical to good eyesight development. For instance, a study published earlier by a research team at Australia’s Brien Holden Vision Institute found that myopia progression in Chinese children is up to 40% slower in summer, when they are exposed to more sunlight, than in winter.

Speaking of which, the King’s College study found that children born in the summer had almost twice the risk of developing shortsightedness later in life. The authors explain that this may be due to the fact that these children start school earlier in life.

What was surprising to learn was that  children born by fertility treatment had a 37% reduced risk of myopia by the time they were in their mid-teens. Another interesting new factor identified by the researchers was that for every higher level of education the mother had, the risk of her child having myopia rose by 33%. This latter factor may be pinned to the link between myopia and intelligence or to the fact that educated mother may encourage their children to study harder indoors.

“Given the rise in myopia prevalence, likely due to changing environmental pressures in childhood, further studies of this and other cohorts are warranted, in conjunction with genetic data, to continue efforts to produce predictive models that can ascertain who should be targeted for treatments to reduce the future burden of this condition,” the authors concluded.