Bifocals worked better than single-vision glasses to slow nearsightedness in children whose sight was deteriorating most rapidly, according to a study in the Archives of Ophthalmology. Researchers randomly assigned 153 of these children, ages 8 to 13, to wear either single-vision glasses, standard bifocals or so-called prismatic bifocals for two years. Though the eyesight of children in each group worsened throughout the study, children who wore standard bifocals required one-third less subsequent correction than children who wore single-vision glasses. Children who wore the prismatic bifocals, which permit the wearer to adjust the focus of the near-viewing lens, fared even better, requiring about one-half as much subsequent correction as children who wore single-vision lenses. Though the precise reason why bifocals slow the progress of myopia is unclear, they may work by reducing eyestrain, which contributes to nearsightedness.
Caveat: Because of the study’s time frame, it is not known whether bifocals slow nearsightedness permanently or merely during childhood. Previous studies have reported mixed results regarding the effects of bifocals on nearsightedness, in part because they have focused on children with milder myopia, the researchers suggested. (“Randomized Trial of Effect of Bifocal and Prismatic Bifocal Spectacles on Myopic Progression,” 1/11/2010)