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
References in periodicals archive ?
Recall that the patient wants bifocal lenses, and it is worth noting at this point that vertical differential prismatic effects can be generally worked out by consideration of the distance portion; if the segment size, heights, and additions are the same in each eye, then the vertical prismatic effects due to the segment cancel each other out.
In my case I had them place the bifocal in the upper part of my right lens.
For example, insurers and their commercial policyholders need to apply bifocal vision to cyber risk.
While the results of a subgroup of studies showed that there was no significant gender-related difference in the eye's ability to focus clearly on objects at near distances, the overall analysis provided evidence that women have a need for higher power reading glasses or bifocals than men of an equivalent age.
Nobody is immune from this condition, and unchecked it inevitably means reading glasses, bifocals or varifocals.
My bifocals and I are making our way through this brave new invisible-line world where what you see depends on how you hold your eyes.
I am having a very difficult time adapting to my first pair of bifocals. Please keep in mind that many of your readers are over 40!
What do bifocals, paper money, and lightning rods have in common?
With its premium intraocular lenses (marketed under the name Crystalens), Eyeonics is working toward enabling patients to have cataract surgery and be able to leave their bifocals at the hospital.
After a great deal of frustration with my new bow, I came to the conclusion that with my eyesight and bifocals I simply could not use a peep sight.