Regarding Progressive Glasses, also called progressive addition lenses (PAL), progressive power lenses, graduated lenses, no-line bifocals, and varifocal lenses, are used in to correct and other disorders of. They are characterized by a gradient of increasing, added to the wearer's correction for the other. The gradient starts at a minimum, or no addition power, at the top of and reaches a maximum addition power, at the bottom of the lens. The length of the progressive power gradient on the lens surface is usually between 15 and 20 mm with a final addition power between +1.00 to +2.50 for most wearers. The addition value prescribed depends on the level of of the patient and is closely related to age.
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