A Comparison of the Long-Term Effects of Dorzolamide 2% and Brinzolamide 1%, Each Added to Timolol 0.5%, on Retrobulbar Hemodynamics and Intraocular Pressure in Open-Angle Glaucoma Patients

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To compare the effect on the retrobulbar hemodynamics and intraocular pressure (IOP) of dorzolamide 2% and brinzolamide 1%, each added to timolol 0.5% in patients with primary open-angle glaucoma (POAG). 146 POAG patients were prospectively randomized to receive either dorzolamide 2% or brinzolamide 1% BID, each added to timolol 0.5%, during a 60-month evaluator-masked study. At baseline and every 6 months for 60 months, we measured the retrobulbar hemodynamic parameters in the ophthalmic artery (OA), central retinal artery (CRA), and short posterior ciliary arteries (SPCA) using color Doppler imaging (CDI), intraocular pressure (IOP), and blood pressure measurements. Dorzolamide significantly increased the end-diastolic velocity (EDV) in the OA in 1.22 cm/s, 95% confidence interval (95% CI) 0.90-1.56 cm/s, P < 0.001 and reduced the resistivity index (RI) in the OA in 0.04 units, 95% CI 0.03-0.05, P < 0.001. None of the retrobulbar parameters changed significantly on therapy with brinzolamide when the results were analyzed at month 60. Both dorzolamide and brinzolamide significantly decreased IOP (-4.3, 95% CI -4.5 to -4.2 mmHg and -4.3, 95% CI -4.4 to -4.2 mmHg, respectively). Dorzolamide significantly reduced the RI in the OA from 0.74 (0.02) to 0.70 (0.02), CRA from 0.66 (0.02) to 0.62 (0.02), and SPCA from 0.66 (0.02) to 0.62 (0.02), P < 0.001, respectively. Our results suggest augmented retrobulbar blood flow after 5 years of treatment with dorzolamide but not with brinzolamide, each added to timolol, in POAG patients.