Farsightedness, also called longsightedness, is a visual defect in which a person can see distant objects clearly, but near vision may be blurred. Doctors call this condition hyperopia. In most cases of farsightedness, the eyes are too short from front to back. As a result, light rays from an object reach the retina before they can be brought into focus.
The eye may be able to correct its own farsightedness through a process called accommodation. In accommodation, certain muscles in the eye contract, making the lens of the eye rounder and thicker. The lens then has a greater ability to focus. The lens of a normal eye accommodates only to bring nearby objects into focus. But the lens of a farsighted eye must also accommodate for sharp distance vision. Although a farsighted eye receives sharp images of distant objects, the excessive accommodation may cause eyestrain and headaches. In addition, the lens may not accommodate enough for sharp near vision.
Young people and mildly farsighted people can accommodate enough for sharp vision at both near and far distances. As a person grows older, however, the lens begins to lose its ability to accommodate. Many farsighted people first notice the condition at that time. Farsightedness is easily corrected with eyeglasses or contact lenses. As an alternative, doctors may use high-frequency radio waves to change the shape of the cornea in a technique called conductive keratoplasty. Laser surgery also may be used to reshape the cornea.
See also Eye (Farsightedness); Glasses (Prescription glasses); LASIK surgery.
