bifocal

bifocal /bi·fo·cal/ (bi-fo´-) (bi´fo-k'l)

1. having two foci.

2. containing one part for near vision and another part for distant vision, as in a bifocal lens.

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bi·fo·cal (b-fkl, bf-)

adj.

1. Having two focal lengths.

2. Having one section that corrects for distant vision and another that corrects for near vision.

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bifocal

[bīfō′kəl]

Etymology: L, bis + focus, hearth

1 pertaining to the characteristic of having two foci.

2 (of a lens) having two areas of different focal lengths.

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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.