nearsightedness or myopia, defect of vision in which far objects appear blurred but near objects are seen clearly. Because the eyeball is too long or the refractive power of the eye's lens is too strong, the image is focused in front of the retina rather than upon it. Corrective eyeglasses with concave lenses compensate for the refractive error and help to focus the image on the retina. Hard corneal contact lenses or soft hydrophilic contact lenses are another option, usually offering better acuity and peripheral vision than do eyeglasses. (Contact lenses may be troublesome for people who tend to get eye infections or have hand tremors, however.) Nearsightedness can also be corrected by using laser cornea surgery and a device called a microkeratome to flatten the eye, or by surgically implanting a corrective lens behind the iris.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.