Objective: To estimate the intraocular pressure (IOP)-lowering effect of 2% dorzolamide or 0.005% latanoprost when added to 0.5% timolol.
Design: Meta-analysis of randomized clinical trials.
Participants: Seventeen articles reporting on 19 study arms with 5 possible treatment combinations and 4 study arms serving as controls.
Methods: Articles written in English, German, French, or Dutch and published up to December 2004 were identified in Medline, Embase, the Cochrane Controlled Trials Register, and references from relevant articles. For the article to be considered, over 85% of the patients had to have primary open-angle glaucoma or ocular hypertension. The pooled 1- to 3-month additional IOP-lowering effect after a run-in phase on timolol was calculated by performing meta-analysis using the random effects model.
Main outcome measures: Absolute and relative changes in IOP after run-in on timolol for peak moment, trough moment, or mean diurnal curve.
Results: The pooled change from baseline [mean (95% confidence interval)] for 0.5% timolol varied from -0.7 mmHg (-1.2 to -0.2, for the mean diurnal curve) to -2.0 mmHg (-1.3 to -2.7, at peak). Pooled changes for 2% dorzolamide in concomitant use with 0.5% timolol were -4.1 mmHg (-4.4 to -3.8) at trough and -4.9 mmHg (-5.3 to -4.5) at peak. The fixed 2% dorzolamide and 0.5% timolol combination resulted in a pooled change of -3.8 mmHg (-4.2 to -3.4) at trough and -4.9 mmHg (-5.3 to -4.5) at peak. The concomitant use of 0.005% latanoprost and 0.5% timolol gave a pooled change from baseline of -6.0 mmHg (-6.8 to -5.2) at the mean diurnal curve. The fixed combination of 0.005% latanoprost and 0.5% timolol resulted in a mean change of -3.0 mmHg (-3.8 to -2.2) at the mean diurnal curve.
Conclusion: In this meta-analysis of clinical trials, the addition of dorzolamide or latanoprost further lowers IOP in eyes on timolol. This result may not be generalizable because these trials may have included nonresponders to timolol.