Objective: It is difficult to rank treatments according to their effect size when several treatments are available and not all treatments have been compared directly. The purpose of this study was to show a new statistical technique (network meta-analysis) to address this problem and to rank glaucoma drugs according to their intraocular pressure (IOP)-reducing effect.
Study design and setting: Network meta-analysis of randomized controlled trials was used to combine direct and indirect estimates of the effect of eight drugs and placebo from 28 randomized controlled trials in patients with primary open-angle glaucoma or ocular hypertension patients, 6,841 for the peak effect and 6,953 patients for the trough effect.
Results: All drugs differ from placebo in lowering IOP. At the peak, the rank order from high to low in terms of the mean IOP reduction reached is bimatoprost, travoprost and latanoprost, brimonidine, timolol, dorzolamide, betaxolol, brinzolamide. At the trough, this rank order is bimatoprost, latanoprost, travoprost, timolol, betaxolol, dorzolamide, brinzolamide, brimonidine. The results based on direct or indirect estimates were similar. This ranking differed from the ranking based on the mean IOP change from baseline of all arms including the study drug from all randomized controlled trials.
Conclusions: A network meta-analysis can be used to combine direct and indirect treatment effects in a formal way. Applied to glaucoma medications, it shows that there is a rank order in treatment effects on IOP.