bifocal

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bifocal

 [bi´fo-kal]
of a lens, having two areas with different refractive powers.
bifocal glasses eyeglasses in which each lens is made up of two segments of different refractive powers, or strength. Generally, the upper part of the lens is used for ordinary or distant vision, and the smaller, lower section for near vision, for close work such as reading or sewing. Bifocal eyeglasses may be prescribed for presbyopia, which often occurs with aging.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

bi·fo·cal

(bī-fō'kăl),
Having two foci.
Farlex Partner Medical Dictionary © Farlex 2012

bifocal

(bī-fō′kəl, bī′fō′-)
adj.
1. Having two focal lengths.
2. Having one section that corrects for distant vision and another that corrects for near vision, as an eyeglass lens.
3. Having two distinct goals or objects of attention: a bifocal approach to the problem.
pl.n. bifocals (bī′fō′kəlz, bī-fō′-)
Eyeglasses with bifocal lenses.

bi·fo′cal·ism n.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

bi·fo·cal

(bī-fō'kăl)
Having two foci.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

bifocal

Having two different foci. In bifocal spectacles each lens has a lower segment of greater power for convenience in reading.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005