The effects of dorzolamide 2% and dorzolamide/timolol fixed combination on retinal and optic nerve head blood flow in primary open-angle glaucoma patients

Abstract

Purpose: To compare the effect of dorzolamide hydrochloride 2%, timolol maleate 0.5%, and their fixed combination on intraocular pressure (IOP) and retinal and optic nerve head haemodynamics in primary open-angle glaucoma patients. Methods: Twenty-eight patients with early-moderate glaucomatous damage treated with β-blockers (>6 months) with IOP values ranging from 18 to 22 mmHg at trough participated in this trial. After a 4-week washout period, patients were randomized in two groups: group I started with dorzolamide 2% monotherapy and group II with timolol 0.50% monotherapy for 4 weeks. After this period, both groups switched to dorzolamide/timolol fixed combination for 4 weeks. IOP, ocular diastolic perfusion pressure (ODPP), heart rate, and Scanning Laser Doppler Flowmetry measurements at the peripapillary retina and neuroretinal rim were taken at T0 (enrolment), T1 (wash out), T2 (monotherapy), and T3 (dorzolamide/timolol). Data were compared between different study times. Statistical analysis was conducted using a paired t-test. Results: Between T1 and T3, IOP decreased significantly in group I (-21.40%) (P<0.001) and in group II (-21.25%) (P<0.001). At the same time intervals, blood flow increased significantly at rim level for group I (+30.03%) (P<0.05) and also when all patients were considered (rim +17.99%) (P<0.05). Between T1 and T3, we also observed a significant increase of ODPP in group I (+7.24%) (P<0.01) and in group II (+6.08%) (P<0.05) and when all patients were considered (+8.43%) (P<0.01). Conclusions: Dorzolamide/timolol fixed combination increased blood flow significantly at the neuroretinal rim showing a combination of hypotensive and haemodynamic effects.