Effects of topical dorzolamide on retinal and retrobulbar hemodynamics

. Purpose: Topical carbonic anhydrase inhibitors such as dorzolamide have been developed as ocular hypotensive agents devoid of the side effects plaguing their systemic predecessors. We evaluated the influence of dorzolamide on retinal and retrobulbar blood flow markers to determine if the drug has orbital vascular as well as ocular hypotensive effects. Methods: Eleven persons with healthy eyes received either placebo or two drops 2% dorzolamide, 2 h prior to studies conducted in double-masked, counterbalanced fashion. Four retrobulbar vessels (nasal and temporal posterior ciliary, central retinal, and ophthalmic arteries) were analyzed by color Doppler imaging; scanning laser ophthalmoscopy was used to examine retinal and superficial optic nerve head blood linear velocity. Results: Dorzolamide lowered IOP from 15.7 ± 0.7 to 13.7 ± 0.7 mmHg (p < 0.05). The drug also hastened retinal arteriovenous passage of fluorescein dye, and accelerated capillary dye transit in the macula and optic nerve head. The drug, however, left unaltered blood velocity or resistance index in any retrobulbar vessel. Conclusions: Dorzolamide is an effective ocular hypotensive agent that accelerates blood velocity in the retinal and superficial optic nerve head without an apparent effect upon retrobulbar hemodynamics.