Nearsightedness occurs if your eyeball is too long or the cornea has too much curvature, so the light entering your eye is not focused correctly. Nearsightedness is a very common vision condition that affects nearly 30 percent of the U.S. population.
Some evidence supports the theory that nearsightedness is hereditary.
There is also growing evidence that nearsightedness may be caused by the stress of too much close vision work. It normally first occurs in school age children. Since the eye continues to grow during childhood, nearsightedness generally develops before age 20. A sign of nearsightedness is difficulty seeing distant objects like a movie or TV screen or chalkboard. A comprehensive optometric examination will include testing for nearsightedness.