Saturday, March 03, 2012

How Does Nearsightedness Develop in Children?

This article obviously is about simple myopia. It does not mention degenerative myopia, also known as malignant, pathological, or progressive myopia. This is caused by the abnormal growth of the eyeball. True that the lens does not adapt to it, but the overly long eyeball causes problems such as retinal detachment and macular degeneration.

http://www.sciencedaily.com/releases/2012/03/120301113258.htm

ScienceDaily (Mar. 1, 2012) — Myopia (nearsightedness) develops in children when the lens stops compensating for continued growth of the eye, according to a study in the March issue of Optometry and Vision Science, official journal of the American Academy of Optometry.

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Myopia or nearsightedness -- difficulty seeing objects at a distance -- develops in about 34% of American children as they grow. Vision professionals and scientists typically think of myopia as a problem occurring when the eyeball becomes too long (front to back) for the optical power of the cornea and lens.

[...]

They found that, in children without myopia, the lens grew thinner and flatter to maintain normal vision as the eye grew. This adaptation maintained a normal balance between the optical power of the lens and the increasing length of the eyeball. From age nine months to nine years, eyeball length increased by an average of three millimeters.

However, in children who developed myopia, the lens stopped changing in response to eye growth. Nearsightedness developed not just because of increases in the length of the eyeball, but rather because the optical power of the lens no longer changed as the eye grew.

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