title: Randomized trial of effect of bifocal and prismatic bifocal spectacles on myopic progression: two-year results.
abstract: 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 > or =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).
  
  
  METHODS
  Myopic progression measured by an automated refractor under cycloplegia and increase in axial length (secondary) measured by ultrasonography 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 0.41 mm (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 single-vision 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.
authors.affiliation: School of Optometry, Faculty of Health and Vision Improvement Domain, Queensland University ofTechnology, Brisbane, Australia. . descheng@hotmail.com
authors.forename: Desmond
authors.initials: D
authors.lastname: Cheng
authors.forename: Katrina L
authors.initials: KL
authors.lastname: Schmid
authors.forename: George C
authors.initials: GC
authors.lastname: Woo
authors.forename: Bjorn
authors.initials: B
authors.lastname: Drobe
mesh_terms: D000293:Adolescent; D044466:Asian People / Q000208:ethnology; D002170:Canada / Q000453:epidemiology; D002648:Child; D018450:Disease Progression; D005139:Eyeglasses; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D009216:Myopia / Q000208:ethnology / Q000503:physiopathology* / Q000628:therapy*; D011379:Prognosis; D012029:Refraction, Ocular; D014792:Visual Acuity / Q000502:physiology