Purpose: The Convergence Insufficiency Treatment Trial (CITT) Investigator Group conducted a preliminary study assessing the effectiveness of home-based push-up therapy and office-based vision therapy/orthoptics for the treatment of convergence insufficiency (CI). The CITT group developed a placebo therapy program that was designed to simulate real vision therapy/orthoptics. The purpose of this paper is to evaluate the effectiveness of this placebo therapy program in maintaining masking of subjects randomized to the office-based treatment arms (real or placebo).
Methods: Subjects (ages 9 to 30 years) were enrolled, stratified into two groups by age, and then randomly assigned to one of three treatment groups: pencil push-up therapy, office-based vision therapy/orthoptics, or office-based placebo vision therapy/orthoptics. At the end of treatment, subjects in the two office-based therapy groups (placebo and real) were asked: (1) which treatment do you think you received? and (2) how sure are you about your answer?
Results: Ninety-five percent of subjects assigned to real therapy and 83% assigned to placebo therapy thought they were in the real therapy group. Of the subjects who thought they received real therapy, 90% assigned to real therapy and 89% assigned to placebo therapy were "somewhat sure," "pretty sure," or "very sure" of their answer. Those assigned to real therapy had more responses in the "very sure" category.
Conclusion: The CITT placebo therapy program was effective in maintaining subject masking in this multicenter clinical trial.