Comparative Analysis of the Effects of Brimonidine and Dorzolamide on Ocular Blood Flow Velocity in Patients with Newly Diagnosed Primary Open-Angle Glaucoma

Abstract

The aim of this study was to evaluate the effects of brimonidine 0.2% and dorzolamide 2% on the ocular blood flow velocity in patients with newly diagnosed primary open-angle glaucoma (POAG). Forty-four (44) patients with newly diagnosed POAG were included in a prospective, comparative, randomized clinical study. Twenty-six (26) healthy volunteers, whose age and gender matched, were recruited to compare the baseline hemodynamic characteristics of the patients. After a complete eye examination, baseline blood flow velocity measurements of the retrobulbar vessels were made with color Doppler ultrasonography. Patients were randomly assigned to receive either brimonidine 0.2% or dorzolamide 2% for a 3-month period. Blood flow velocity measurements were repeated after 3 months. Both brimonidine and dorzolamide significantly reduced the intraocular pressure. The baseline ophthalmic artery pulsatility index was higher in patients with POAG than control subjects. Whereas there was a significant increase in peak systolic velocity of the central retinal artery, no significant change was observed in the other vessels with brimonidine and dorzolamide treatment. There was little difference, in terms of ocular blood flow velocity, between newly diagnosed glaucoma patients and control subjects. Both topical brimonidine and dorzolamide significantly reduced the intraocular pressure without altering ocular blood flow velocity in patients with newly diagnosed POAG.

Color Doppler Imaging Analysis of Retrobulbar Blood Flow Velocities in Primary Open-Angle Glaucomatous Eyes: A Meta-Analysis

“…Twenty-three prospective observational studies of 1286 eyes with POAG and 1052 controls were included in the meta-analysis. Eighteen of the studies concerned POAG eyes that received IOP-lowering drugs and had well controlled IOP [14], [21], [28]–[43]; five studies concerned newly diagnosed and untreated POAG [19], [44]–[47]. CDI was conducted in a sitting position in three studies [31], [40], [44] and in a supine position in the remaining 20 studies [14], [19], [21], [28]–[30], [32]–[39], [41]–[43], [45]–[47].…”

Retinal Arteriolar Vascular Reactivity in Untreated and Progressive Primary Open-Angle Glaucoma

“…16 However, the effect of IOP-lowering medications on ocular blood flow remains poorly understood. Most studies have shown no change in retinal blood flow after treatment with timolol 17,18 or brimonidine 19,20 and a decrease in blood velocity of the ophthalmic artery after treatment with xalatan in POAG. 21 In particular, treatment with carbonic anhydrase inhibitors (CAIs) has been reported to increase ocular hemodynamics in POAG, 18,[22][23][24][25][26] to increase cerebral hemodynamics in young subjects, 27 and also to result in an enhanced autoregulation of retinal vessels after treatment with dorzolamide.…”

“…21 In particular, treatment with carbonic anhydrase inhibitors (CAIs) has been reported to increase ocular hemodynamics in POAG, 18,[22][23][24][25][26] to increase cerebral hemodynamics in young subjects, 27 and also to result in an enhanced autoregulation of retinal vessels after treatment with dorzolamide. 28,29 A few studies have found no change 20,30,31 in retinal hemodynamics after CAI treatment. Most of the studies have assessed only the effect of CAIs in either patients receiving prior treatment or after an inadequate washout period.…”

Effects of dorzolamide/timolol fixed combination on retrobulbar hemodynamics in pseudoexfoliative glaucoma

“…On the basis of these observations, it must be emphasized that modern antiglaucoma therapies should aim to affect not only intraocular pressure, but also other factors such as ocular blood flow. Although the effects of topical CAI drugs on ocular blood flow velocities were measured and the evidence obtained from these studies suggests that CAI agents increase the ocular blood flow velocities, the effect of these types of drugs was not investigated on primary open angle glaucoma patients with pseudoexfoliation [3–6,15]. The resistive index lowering effect of dorzolamide can be related to its vasodilator effect on ophthalmic and retinal vessels.…”

“…The major role of carbonic anhydrase inhibitors (CAIs) on intraocular pressure (IOP) is reducing aqueous humor secretion by inhibition of carbonic anhydrase in the ciliary processes. In addition to IOP lowering effect of this group drugs, dorzolamide and brinzolamide also increase the retrobulbar ocular blood flow by arterial vasodilation [3–6]. Several studies, using different methods, indicated that dorzolamide reduced retrobulbar ocular blood flow [7–9].…”