|
Ophthalmology => Farsightedness
Farsightedness
Farsightedness, also called hyperopia, common name for a defect in vision in which a person sees near objects with blurred vision, while distant objects appear in sharp focus.
In normal vision, light rays from an object entering the eye are focused by the lens (transparent tissue that changes shape to help focus incoming light) on the retina (the membrane at the back of the eye that transmits images of external objects to the optic nerve). In people with farsightedness, the distance between the lens and the retina is too short. As a result, light rays from near objects strike the retina before they are in focus, which causes blurred vision. Distant objects appear clearly because light rays from them focus correctly on the retina.
Farsightedness is present at birth and tends to run in families. The condition usually is not severe in young children, and mild cases sometimes correct naturally-as these children grow, eye muscles adjust the distortion of the lens until light rays from near objects focus correctly on the retina, resulting in sharp vision. With age, this natural ability to accommodate the condition is lost.
Persons with farsightedness frequently suffer from eyestrain and headaches in addition to defective vision. Farsightedness usually can be corrected with eyeglasses or contact lenses. The age at which a person requires eyeglasses for this condition depends on its degree of severity. However, almost everyone requires at least reading glasses by the time they are in their 60s to help them see objects that are small but near.
In 1998 the Food and Drug Administration approved the use of laser surgery to correct or diminish farsightedness. Doctors who specialize in disorders of the eye, called ophthalmologists, use one of two forms of laser surgery to reshape the eye, thereby reducing or eliminating the need for corrective lenses. In photorefractive keratectomy (PRK), an ophthalmologist uses a laser beam to sculpt the edges of the cornea, a thin membrane adjacent to the lens. With laser in situ keratomileusis (LASIK), the ophthalmologist uses a laser beam and a tiny blade to make similar corrections to the cornea.
Back
|
