Randomized trial of effect of bifocal and prismatic bifocal spectacles on myopic progression two-year results

Objective: To determine whether bifocal and prismatic bifocal spectacles could control myopia in children with high rates of myopic progression. Methods: This was a randomized controlled clinical trial. One hundred thirty-five (73 girls and 62 boys) myopic Chinese Canadian children (myopia of ≥1.00 diopters [D]) with myopic progression of at least 0.50 D in the preceding year were randomly assigned to 1 of 3 treatments: (1) single-vision lenses (n=41), (2)+ 1.50-D executive bifocals (n=48), or (3) + 1.50-D executive bifocals with a 3-prism diopters base-in prism in the near segment of each lens (n=46). Main Outcome Measures: Myopic progression measured by an automated refractor under cycloplegia and increase in axial length (secondary) measured by ultra-sonography at 6-month intervals for 24 months. Only the data of the right eye were used. Results: Of the 135 children (mean age, 10.29 years [SE, 0.15 years]; mean visual acuity, -3.08 D [SE, 0.10 D]), 131 (97%) completed the trial after 24 months. Myopic progression averaged -1.55 D (SE, 0.12 D) for those who wore single-vision lenses, -0.96 D (SE, 0.09 D) for those who wore bifocals, and -0.70 D (SE, 0.10 D) for those who wore prismatic bifocals. Axial length increased an average of 0.62 mm (SE, 0.04 mm), 0.41 mm (SE, 0.04 mm), and 0.41mm(SE, 0.05 mm), respectively. The treatment effect of bifocals (0.59 D) and prismatic bifocals (0.85 D) was significant (P<.001) and both bifocal groups had less axial elongation (0.21 mm) than the singlevision lens group (P<.001). Conclusions: Bifocal lenses can moderately slow myopic progression in children with high rates of progression after 24 months. Applications to Clinical Practice: Bifocal spectacles may be considered for slowing myopic progression in children with an annual progression rate of at least 0.50 D. Trial Registration: clinicaltrials.gov Identifier: NCT00787579