title: Evaluation of masking study participants to intravitreal injections in a randomized clinical trial.
abstract: OBJECTIVE
  To evaluate the success of masking study participants to treatment allocation using sham intravitreal injections.
  
  
  METHODS
  Eyes were randomized to receive sham injections plus prompt laser, intravitreal ranibizumab injections plus prompt laser, intravitreal ranibizumab injections plus deferred laser, or intravitreal triamcinolone acetonide injections plus prompt laser up to every 16 weeks with sham injections intermittently. All eyes could receive treatment or sham as often as every 4 weeks. Participants with 2 study eyes had 1 eye randomized to sham plus prompt laser and 1 eye randomized to a real injection group. Sham injections were performed by pressing the syringe hub against the conjunctiva to mimic a real injection. Laser treatment was not masked. At the 1-year visit, participants were asked if they believed that the injections received during the study were real, sham, or sometimes real and sometimes sham.
  
  
  RESULTS
  Among 423 participants with 1 study eye, the correct assignment was stated by 9.9% of the sham plus prompt laser group, 88.0% of the ranibizumab plus prompt laser group, 89.6% of the unmasked ranibizumab plus deferred laser group, and 44.0% of the triamcinolone plus prompt laser group. Among 112 participants with 2 study eyes, the correct assignment was stated for 24.1% of the sham plus prompt laser eyes.
  
  
  CONCLUSIONS
  Successful masking of an intravitreal injection can be accomplished when a sham injection procedure carefully mimics a real injection procedure. Masking seems less successful when one eye is receiving a real injection and the other eye is receiving a sham injection or when an individual eye receives both real and sham injections.
authors.affiliation: Jaeb Center for Health Research, Tampa, FL 33647, USA. drcrstat2@jaeb.org
authors.forename: Adam R
authors.initials: AR
authors.lastname: Glassman
authors.forename: Cynthia R
authors.initials: CR
authors.lastname: Stockdale
authors.forename: Roy W
authors.initials: RW
authors.lastname: Beck
authors.forename: Carl
authors.initials: C
authors.lastname: Baker
authors.forename: Neil M
authors.initials: NM
authors.lastname: Bressler
mesh_terms: D000368:Aged; D020533:Angiogenesis Inhibitors / Q000008:administration & dosage*; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage*; D015982:Bias; D003131:Combined Modality Therapy; D003930:Diabetic Retinopathy / Q000188:drug therapy* / Q000503:physiopathology; D004311:Double-Blind Method; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage*; D006801:Humans; D058449:Intravitreal Injections; D017075:Laser Coagulation; D008297:Male; D008875:Middle Aged; D010361:Patients / Q000523:psychology; D000069579:Ranibizumab; D014222:Triamcinolone Acetonide / Q000008:administration & dosage*; D014792:Visual Acuity / Q000502:physiology
chemical_list: D020533:Angiogenesis Inhibitors; D061067:Antibodies, Monoclonal, Humanized; D005938:Glucocorticoids; D014222:Triamcinolone Acetonide; D000069579:Ranibizumab