The sharp increase in myopia

Myopia remains a mystery. We know how to correct the sight surgically, we know the "mechanics" of the eye, but we still know very little about the origins and causes.

A recent study from this point of view rather disturbing: American researchers come together to see that the rate of myopia raised in the U.S. from about 25% in the early 1970s to almost 42% in the early 2000s (Archives of Ophthalmology, December 2009).

To achieve this, the researchers used data collected from national health surveys. In 1971-1972 there were more than 5,000 people aged 12 to 54 years, in 1999-2004 nearly 10,000 people. Recent data is based on the same criteria as those used in the early 1970s for myopia.

There was 25% of myopic and thirty-three years later, they are 41.6%. Blacks (from 13% to 33.5%) as whites (from 26.3% to 43%) underwent the same evolution. Myopia is a defect of the eye. Images form not on the retina but in front of it. The eye can be compared to a camera: the cornea is the outer pane, the pupil, the iris, the lens is the zoom and the retinal is the receptor layer. A myopic eye can no longer form sharp images on the retina for distant objects.

U.S. researchers conclude their study with a call for research: Identifying the risk factors responsible for the increase of myopia could afford to build low-cost strategies of struggle. It is estimated that causes of myopia is multifactorial.

The two main factors, besides age, are heredity and environmental factors. It is well established that certain severe cases of myopia are related to genetics. Being born into a family without myopic decreases the risk. Otherwise, the risk is greatly increased. Some forms of eye predispose them to this abnormality. But we also know that nutrition, lifestyle, residence, cultural level, the number of years of education, frequent use of computer monitors or television for example, play a role in evolution of myopia.

The frequency of use of near vision may also be a contributing factor to myopia but there are many other competing theories such as light exposure in childhood.

No doubt that our modern lifestyle promotes myopia, and probably accelerates its appearance. Unfortunately it is still impossible to quantify what factor is the most important.

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