What Does Progressive Wear Mean With Regard to Glasses?

Progressive addition lenses (PALs), often referred to simply as progressive lenses, are eyeglass lenses that offer three visual correction powers --- distance, intermediate and near --- in each lens.

Presbyopia

• As the eye's natural lens ages, it loses its ability to focus on objects at arm's length or closer. Most people, even those without prior vision problems, begin to experience this condition around the age of forty when they have difficulty focusing on fine print within reading or close distance. At first, this condition can be corrected by holding reading material further away. As presbyopia progresses, however, correction for close and intermediate distances may be required. The condition worsens in most people for several years but begins to stabilize at around sixty years of age.

Treatment

• Several options exist for correcting presbyopia. Reading glasses may be purchased either by prescription or over-the-counter. These work well for close distances only, leaving everything else out of focus. Multifocal lenses are another option for correcting presbyopia and are especially well-suited to prescription eyeglass wearers. As the name suggests, multifocal lenses -- including bifocals, trifocals and progressives -- contain multiple vision correction powers in each lens. Bifocals allow one to focus on both distant and close objects; a visible line on the eyeglass lens separates both powers. Over time, presbyopia may worsen to the point where one has trouble focusing on objects of intermediate distance, such as a computer monitor. Trifocal lenses address this problem by correcting for far, intermediate and close visual distances. While bifocals and trifocals work well for many people, others find the visible lines to be aesthetically unpleasant. Additionally, the quick change in power may take some getting used to. Progressive lenses address both of these problems; they correct all three visual distances without lines and offer gradual transitions from one power to the next.

Progressive Lenses

• Progressive lenses are an advanced type of trifocal lenses. They allow one to focus on objects at near, intermediate and far distances. Unlike trifocals, the lines separating the three powers are invisible. Also, the transition from one power to the next in progressive lenses is gradual, eliminating a common problem in bifocals and trifocals known as "image jump". One disadvantage of progressive lenses is the loss of peripheral vision. Because of the way the lenses are manufactured, the area to the bottom-left and bottom-right of each lens is blurred, typically leading to a longer adjustment period for those new to progressive lenses vs. those new to bifocals or trifocals.