Objective To assess the intraocular pressure (IOP) lowering effect of single and multiple glaucoma medications in a clinical effectiveness cohort of primary open angle glaucoma (POAG) patients from the CyPass microstent randomized controlled trial (COMPASS).
Methods This is a Multi-center interventional consecutive series. A total of 128 consecutive subjects with confirmed POAG were included in the cases series. Subjects on topical glaucoma treatment underwent standardized IOP medication wash-out up to 30 days. Three consecutive masked IOP measurements were taken both at baseline and after wash-out. Subjects also underwent diurnal IOP measurement after wash-out. At entry, there were 63, 31 and 19 subjects on 1,2 and 3 medications, in addition to 15 untreated subjects. IOP lowering effect of topical medications was assessed by observing IOP elevation post standardized wash-out.
Results Mean medicated entry IOP for the 1,2 and 3 medication groups was similar at 17.4, 17.9 and 17.3 mmHg respectively. Subjects on 1 medication had a 34% mean increase in IOP after medication removal, while subjects on 2 and 3 medications had 43% and 46% IOP increase respectively, demonstrating diminishing effect of dual and triple medication therapy. Between 15-30% of medicated subjects had less than 20% IOP medication effect post wash-out. Even when on 3 medications, more than 10% of subjects showed almost no treatment effect with less than 10% change in IOP post wash-out.
Conclusion Clinical effectiveness of IOP lowering medications for the treatment of POAG has diminishing effect when multiple topical agents are used together and minimal effect from the addition of a third topical medication.