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A randomized trial of the effect of single-vision vs. bifocal lenses on myopia progression in children with esophoria
G W Fulk1, L A Cyert, D E Parker
1College of Optometry, Northeastern State University, Tahlequah, Oklahoma 74464-7017, USA. fulk@cherokee.nsuok.edu
Background:
Bifocals have long been thought to reduce progression of childhood myopia. However, this hypothesis has not been definitively evaluated.
Methods:
We conducted a randomized clinical trial to test the hypothesis that bifocals slow myopia progression in children with near-point esophoria. Eighty-two myopic children were randomized to single-vision glasses (n = 40) or to bifocals with a +1.50 D add (n = 42) and were followed for 30 months. Refraction was measured by an automated refractor after cycloplegia. The primary outcome was myopia progression defined as the difference between the spherical equivalent at baseline and at the 30-month examination, averaged over both eyes.
Results:
Follow-up was incomplete for six children in the bifocal group and one child in the single-vision group. Among the children completing the 30 months of follow up, myopia progression (mean spherical equivalent of the two eyes) averaged 0.99 D for bifocals and 1.24 D for single vision (unadjusted, p = 0.106; adjusted for age, p = 0.046). Treatment groups differed in their cumulative distributions (Kolmogorov-Smirnov procedure, p = 0.031). Evidence for a treatment effect on growth in vitreous chamber depth was similar (p = 0.046 by K.S.).
Conclusion:
Use of bifocals, instead of single-vision glasses, by children with near-point esophoria seemed to slow myopia progression to a slight degree.