Progressive lenses, also called progressive addition lenses (PAL), progressive power lenses, graduated lenses,and varifocal lenses, are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation. The wearer can adjust the additional lens power required for clear vision at different viewing distances by tilting his or her head to sight through the appropriate part of the vertical progression. The lens location of the correct addition power for the viewing distance usually only requires small adjustments to head position, since near vision tasks such as reading are usually low in the visual field and distant objects higher in the visual field. Progressive addition lenses avoid the discontinuities (image-jumps) in the visual field created by bifocal and trifocal lenses and are more cosmetically attractive. Since bifocal and related designs are associated with 'old age', proponents have suggested the lack of segments on the lens surface of a progressive lens appears more 'youthful' since lenses associated with younger wearers [single vision] lenses tend to be free of segments or lines on the surface.
These are the differences between Reading glasses, Bi-Focals & Progressive Lenses:
