People whose professions entail much reading during either training or performance of the occupation have higher degrees of myopia

Professor Douglas Frederick, University of California San Francisco

He said in aboriginal peoples the rates of myopia were rising from virtually nothing to similar levels to those found in Western populations, as they are exposed to Western education systems.

Professor Frederick looked at a wide body of research already carried out into short-sightedness for his paper.

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He said the patterns of short-sightedness were not just linked to childhood habits.

"People whose professions entail much reading during either training or performance of the occupation have higher degrees of myopia, and the myopia may progress not just in people's teenage years, but throughout their 20s and 30s."

He said there was not a direct link between high intelligence and short-sightedness as had been presumed.

The link is more likely to be that people have studied hard and therefore achieved academic success - and possibly myopia.

Short-sightedness can run in families, so Professor Frederick suggests habits such as reading with a book to close to the face could go unchecked, worsening the condition.

In people who are short-sighted, the eyeball is too long or the lens too curved to focus an image on a retina.

It usually first becomes apparent in older children and teenagers.