bifocal glasses

glasses /glass·es/ (glas´iz) spectacles; lenses arranged in a frame holding them in the proper position before the eyes, as an aid to vision.

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bifocal glasses  those with bifocal lenses.

trifocal glasses  those with trifocal lenses.

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bifocal glasses

Etymology: L, bis, twice, focus, hearth; AS, glaes

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.

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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.

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glasses [glas´ez]

lenses arranged in a frame holding them in the proper position in front of the eyes, as an aid to vision. Called also eyeglasses and spectacles.

bifocal glasses glasses with bifocal lenses; see also bifocal glasses.

trifocal glasses glasses with trifocal lenses.