title: Visual acuity outcomes among sham vs no-treatment controls from randomized trials.
abstract: OBJECTIVE
  To compare 2-year visual acuity outcomes between similar participants assigned to sham and no-treatment control arms in randomized clinical trials.
  
  
  METHODS
  We retrospectively matched sham controls from 2 randomized trials to no-treatment controls (no sham or placebo) from 3 trials on 8 baseline prognostic criteria (full matches) or on 4 to 7 criteria (partial matches). Outcomes were compared using data from those who had 2-year visual acuity measurements and also using the last observation carried forward method to impute missing 2-year measurements.
  
  
  RESULTS
  A full match to a no-treatment control was identified for 72 of 321 sham controls (22%); a partial match was identified for another 93 sham controls (29%). Among the fully matched pairs, no important difference in 2-year visual acuity outcomes was observed. However, 2-year outcomes differed somewhat between sham and no-treatment controls within the partially matched pairs.
  
  
  CONCLUSIONS
  Findings from fully matched pairs suggest that sham treatment to mask participants in clinical trials may be unnecessary when visual acuity is the outcome of interest. However, findings from the partially matched pairs do not fully support this conclusion. This analysis challenges the necessity for sham (placebo) controls in randomized clinical trials in ophthalmology when visual acuity is the primary outcome of interest.
authors.affiliation: Wilmer Eye Institute, School of Medicine, Johns Hopkins University, 550 N Broadway, Room 930, Baltimore, MD 21205-2010, USA. bhawkins@jhmi.edu
authors.forename: Barbara S
authors.initials: BS
authors.lastname: Hawkins
authors.forename: Neil M
authors.initials: NM
authors.lastname: Bressler
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Reynolds
mesh_terms: D020256:Choroidal Neovascularization / Q000188:drug therapy* / Q000503:physiopathology; D006801:Humans; D017075:Laser Coagulation; D008268:Macular Degeneration / Q000188:drug therapy* / Q000503:physiopathology; D016555:Matched-Pair Analysis; D008875:Middle Aged; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use; D010919:Placebos / Q000592:standards*; D011166:Porphyrins / Q000627:therapeutic use; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D012189:Retrospective Studies; D016896:Treatment Outcome; D000077362:Verteporfin; D014792:Visual Acuity / Q000502:physiology*
chemical_list: D017319:Photosensitizing Agents; D010919:Placebos; D011166:Porphyrins; D000077362:Verteporfin