Nearsightedness is most often caused by a natural change in the shape of the eyeball that makes the eyeball too long, so that it is egg-shaped instead of round. This causes light entering the eye to focus in front of the retina instead of directly on the retina, causing blurry vision.

In a person with nearsightedness (myopia), close objects can be seen more clearly than objects that are farther away. Nearsighted people may squint or frown to see things at a distance. They often hold books or other objects close to the face, sit at the front of a classroom or movie theatre, and sit close to the television or computer.

Eyeglasses or contact lenses can help correct nearsightedness. Some people with nearsightedness may also choose to have surgery to change the shape of the cornea, which can reduce nearsightedness.