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Related to bifocal glasses: trifocal glasses
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.
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.
trifocal glasses glasses with trifocal lenses.