bifocal lens

bifocal lens
a lens with two principal focal lengths: the upper part of the lens gives a sharp image of distant objects and the lower part gives a sharp image of near objects, as when reading. Examples are bifocal spectacles, bifocal contact lenses, and bifocal intraocular lenses. See also trifocal lenses, multifocal lenses.

* * *

a lens that has two segments with different refractive powers, ordinarily with the upper for distant and the lower for near vision; used in bifocal glasses.

Medical dictionary. 2011.

Look at other dictionaries:

  • bifocal lens — a lens with two principal focal lengths: the upper part of the lens gives a sharp image of distant objects and the lower part gives a sharp image of near objects, as when reading. Examples are bifocal spectacles, bifocal contact lenses, and… …   The new mediacal dictionary

  • Bifocal — Bi fo cal, n. [Pref. bi + focal.] a bifocal lens. [PJC] …   The Collaborative International Dictionary of English

  • Lens — The transparent structure inside the eye that focuses light rays onto the retina (the nerve layer that lines the back of the eye, senses light and creates impulses that go through the optic nerve to the brain). The lens was named after the lentil …   Medical dictionary

  • lens — n. 1) (in anatomy) the transparent crystalline structure situated behind the pupil of the eye and enclosed in a thin transparent capsule. It helps to refract incoming light and focus it onto the retina. See also: accommodation 2) (in optics) a… …   The new mediacal dictionary

  • bifocal — ► ADJECTIVE ▪ denoting a lens having two parts each with a different focal length, one for distant and one for near vision. ► NOUN (bifocals) ▪ a pair of glasses with bifocal lenses …   English terms dictionary

  • bifocal — ☆ bifocal [bī fō′kəl, bī′fō΄kəl ] adj. adjusted to two different focal lengths n. a lens, esp. for eyeglasses, with one part ground for close focus, as for reading, and the other ground for distance …   English World dictionary

  • bifocal — Having two foci. * * * bi·fo·cal ( )bī fō kəl adj 1) having two focal lengths 2) having one part that corrects for near vision and one for distant vision <a bifocal eyeglass lens> bifocal n 1) a bifocal glass or lens 2) bifocals pl… …   Medical dictionary

  • bifocal — I. adjective Etymology: International Scientific Vocabulary Date: 1888 1. having two focal lengths 2. having one part that corrects for near vision and one for distant vision < a bifocal eyeglass lens > II. noun Date: 1899 1 …   New Collegiate Dictionary

  • bifocal — /buy foh keuhl, buy foh /, adj. 1. Chiefly Optics. having two foci. 2. (of an eyeglass or contact lens) having two portions, one for near and one for far vision. n. 3. bifocals, bifocal eyeglasses or contact lenses. [1885 90, Amer.; BI 1 + FOCAL] …   Universalium

  • bifocal — adjective denoting a lens having two parts each with a different focal length, one for distant and one for near vision. noun (bifocals) a pair of glasses with bifocal lenses …   English new terms dictionary

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