Progressive spectacle lenses, also called progressive addition lenses (PAL), progressive power lenses, graduated prescription lenses, and varifocal or multifocal lenses, are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation.

Eyeglasses that focus continuously from distance to near are known as progressive addition lenses (they are not bifocals).

Progressive addition lenses are similar to bifocals but they are made to have a gradual or blended transition between the two prescriptions.

Instead, prescription glasses, contact lenses, reading glasses, progressive addition lenses, or bifocals can help correct the effects of presbyopia.

Progressive addition lenses avoid the discontinuities (image-jumps) in the visual field created by the majority of bifocal and trifocal lenses and are more cosmetically attractive.

"Correlation analysis of the optics of progressive addition lenses" Sheedy JE Optom Vis Sci.

The progressive addition lens (PAL, also commonly called a progressive or varifocal lens) eliminates the line in bi/tri-focals and is very complex in its profile.

"Progressive Addition Lenses: History, Design, Wearer Satisfaction and Trends" Pope, D R OSA TOPS Vol.

Progressive spectacle lenses, also called progressive addition lenses (PAL), progressive power lenses, graduated prescription lenses, and varifocal or multifocal lenses, are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation.

"Progressive powered lenses: the Minkwitz theorem" Sheedy JE, Campbell C, Optom Vis Sci.

Progressive spectacle lenses, also called progressive addition lenses (PAL), progressive power lenses, graduated prescription lenses, and varifocal or multifocal lenses, are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation.