Effectiveness of placebo therapy for maintaining masking in a clinical trial of vergence/accommodative therapy

PURPOSE. To evaluate the effectiveness of the Convergence Insufficiency Treatment Trial (CITT) placebo therapy program in maintaining masking of patients randomized to the officebased treatment arms, determine whether demographic variables affect masking, and determine whether perception of assigned treatment group was associated with treatment outcome or adherence to treatment.METHODS. Patients (n=221, ages, 9-17 years) were randomized to one of four treatment groups, two of which were office-based and masked to treatment (n=114). The placebo therapy program was designed to appear to be real vergence/ accommodative therapy, without stimulating vergence, accommodation, or fine saccades (beyond levels of daily visual activities).After treatment, patients in the office-based groups were asked whether they thought they had received real or placebo therapy and how confident they were in their answers. RESULTS. Ninety-three percent of patients assigned to real therapy and 85% assigned to placebo therapy thought they were in the real therapy group (P=0.17). No significant differences were found between the two groups in adherence to the therapy (P≥0.22 for all comparisons). The percentage of patients who thought they were assigned to real therapy did not differ by age, sex, race, or ethnicity (P>0.30 for all comparisons). No association was found between patients' perception of group assignment and symptoms or signs at outcome (P≥0.38 for all comparisons).CONCLUSIONS. The CITT placebo therapy program was effective in maintaining patient masking in this study and therefore may have potential for use in future clinical trials using vergence/ accommodative therapy. Masking was not affected by demographic variables. Perception of group assignment was not related to symptoms or signs at outcome (ClinicalTrials.gov number, NCT00338611).