Effect of 3 years of treatment with a dorzolamide/timolol (1%/0.5%) combination on intraocular pressure

PURPOSE We aimed to evaluate the effect on the intraocular pressure (IOP) of a dorzolamide/timolol (1%/0.5%) fixed combination (DTFC) ophthalmic agent for 3 years. PARTICIPANTS A total of 19 consecutive patients who had previously been treated with mono-therapy or any combination of a beta-blocker, carbonic anhydrase inhibitor, or prostaglandin analog, for primary open-angle glaucoma (POAG) (n=5) or normal tension glaucoma (N=14) were enrolled. METHODS Patients were switched to DTFC from their prior glaucoma therapy. The IOP was measured at intervals of 4-6 weeks for 3 years. Treatment failure was defined as an increase of IOP by ≥10% from baseline after switching to DTFC. RESULTS The average IOP decreased significantly from 14.1±2.9 mmHg at baseline to 12.2±2.2, 11.8±2.4, 12.1±2.5, 11.6±1.8, and 12.1±2.7 mmHg at 3, 6, 12, 24, and 36 months, respectively, after switching therapy (all P<0.05). The mean percent decrease of IOP was 12.0%±13.0%, 14.5%±14.2%, 12.2%±18.7%, 16.0%±12.8%, and 12.8%±15.2% at 3, 6, 12, 24, and 36 months, respectively, after switching. Univariate or multivariate analysis revealed the percent decrease of IOP was associated with the type of glaucoma (POAG) at 3 and 12 months, and with the baseline IOP at 3, 12, 24, and 36 months. Kaplan-Meier analysis demonstrated that the percentage of patients who remained on treatment with DTFC was 94.7%, 94.7%, 84.2%, 78.9%, and 78.9% at 3, 6, 12, 24, and 36 months, respectively. Cox proportional hazards analysis showed that the type of glaucoma (POAG) was associated with an increased risk of failure to control the IOP. CONCLUSION The IOP-lowering effect of DTFC was demonstrated for 3 years in this study. The baseline IOP had an important influence on the reduction of IOP achieved by DTFC.