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Are more people nearsighted or farsighted?

About 30 percent of Americans are nearsighted, to some degree, and about 60 percent are farsighted. Nearsighted people have trouble focusing on an image in the distance while farsighted people have trouble focusing on an image close up.

The brain receives a sharply focused picture when light rays entering the pupils of the eye converge (come together) at a single point on the retina. However, if the eyeball is at all misshapen, the light rays will converge at a point in front of the retina (nearsightedness), or behind the retina (farsightedness). Both situations result in blurry vision.

Convex lenses are prescribed to correct farsightedness and concave lenses are prescribed to correct nearsightedness.

Source: Prevention's Giant Book of Health Facts, p. 518.

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