Nearsightedness is a visual condition where a person is able to see things up close, but not far away.

What is going on in the body?

Nearsightedness occurs when light rays entering the front of the eye focus in front of the retina instead of on it. The retina is the membrane in the back of the eye that receives images and carries their signal through the optic nerve to the brain. In most nearsighted people, the light rays don't reach the retina because the eye is too long from front to back. Sometimes the length of the eye is normal but the cornea, the part of the eye that lets in light, is too steep, causing light rays to come together too quickly.

Myopia usually develops in children between the ages of 11 and 13, but can be seen in children much younger. Sometimes the condition does not start until adulthood. Nearsightedness that begins after a person reaches middle age may indicate the start of cataracts. Cataracts are a condition in which the lens, a clear membrane behind the pupil, becomes cloudy.

What are the causes and risks of the condition?

Myopia is caused by:

Myopia is probably genetic, although doing a lot of close-up work may contribute to the condition. The theory is that large amounts of close work fattens the lens, causing nearsightedness.