Nearsightedness, also called myopia, common name for impaired vision in which a person sees near objects clearly while distant objects appear blurred.
In normal vision, light rays from an object enter the eye and are focused by the lens (transparent tissue that changes shape to focus incoming light) onto the retina (the membrane at the back of the eye that transmits images of external objects to the optic nerve). In people with nearsightedness, the distance between the lens and the retina is too long. As a result, light rays from distant objects focus before they strike the retina. Near objects appear clearly because light rays from them focus correctly on the retina.
Nearsightedness is present at birth and tends to be inherited. Unless the condition is severe, it usually goes undetected until early grade school. Nearsightedness is progressive and may advance rapidly during the teenage years. It usually stabilizes in the early 20s, with little subsequent change in vision until after the age of 40. In severe cases, the condition does not moderate and seriously impairs vision.
Nearsightedness can be corrected with eyeglasses or contact lenses that extend the point at which light rays focus. Another option for some nearsighted people is laser surgery. Doctors who specialize in disorders of the eye, called ophthalmologists, use one of two forms of laser surgery to reshape the eye in order to reduce or correct nearsightedness. In photorefractive keratectomy (PRK), an ophthalmologist uses a laser beam to flatten the center and round the edges of the cornea, a transparent membrane adjacent to the lens. With laser in situ keratomileusis (LASIK), the ophthalmologist uses a laser beam and a tiny blade to similarly adjust the shape of the cornea.