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Study results cast doubt on need for placebo controls when visual acuity is primary interest
Arch Ophthalmol. 2009;127(6):725-731.
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A study has challenged the necessity of placebo controls in randomized clinical trials in which visual acuity is the main outcome measure.
"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," the study authors said. "However, findings from the partially matched pairs do not fully support this conclusion."
In the retrospective study, investigators matched sham controls from two randomized clinical trials to no-treatment controls (no sham or placebo) from three trials. Full matches were obtained in trials with eight baseline criteria; partial matches were obtained in trials with four to seven criteria.
Investigators compared outcomes by using data from patients who had 2-year visual acuity measurements and the last observation carried forward method to attribute missing 2-year measurements.
Results showed a full match to a no-treatment control for 72 of 321 sham controls (22%). Data showed a partial match for 93 sham controls (29%).
"Among the fully matched pairs, no important difference in 2-year visual acuity outcomes was observed," the authors said. "However, 2-year outcomes differed somewhat between sham and no-treatment controls within the partially matched pairs."