Article
Article
Eyeglasses and contact lenses
Article By:
Drake, Michael V. Department of Ophthalmology, School of Medicine, University of California, San Francisco, California.
Last reviewed:July 2021
DOI:https://doi.org/10.1036/1097-8542.249800
Lenses worn to improve vision. Eyeglasses and contact lenses are eyewear devices used to correct or improve defective eyesight (see illustration). The primary function of the eye is to focus light energy on the retina. In the optics of a normal eye, parallel rays of light are refracted into sharply focused points of light on the retina. Refraction is necessary because all natural light rays are divergent. See also: Binocular vision disorders; Eye (vertebrate); Eye disorders; Lens (optics); Light; Refraction of waves; Vision; Visual impairment
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