Effect of Topical Corteolol on the Normal Human Retinal Circulation

Abstract

The effect of topical carteolol 1%, a beta-adrenergic blocker with intrinsic sympathomimetic activity, on the retinal circulation was investigated in 15 normal subjects using laser Doppler velocimetry and monochromatic fundus photography. In a double-masked randomized design, one eye received one drop of carteolol 1% and the fellow eye one drop of placebo. Vessel diameter, maximum erythrocyte velocity, and volumetric blood flow rate were determined in a major temporal vein of each eye just before instillation of the drops and then 120 min later. No significant changes in heart rate or mean brachial artery blood pressure were detected after treatment. Intraocular pressure decreased by 28% in the carteolol-treated eye (P < 0.0001) and by 15% in the placebo-treated eye (P < 0.001). No significant changes in vessel diameter, maximum erythrocyte velocity, and volumetric blood flow rate were observed in the carteolol-treated eyes (0.3%, 4.3%, and 3.6%, respectively) or the placebo-treated eyes (0.5%, 5.8%, and 6.7%, respectively). Invest Ophthalmol Vis Sci 33:1853-1856,1992 The influence of timolol maleate, a beta-adrenergic blocking agent, on retinal blood flow has been investigated using bidirectional laser Doppler velocimetry (BLDV) and monochromatic fundus photography (MFP). After a single instillation of timolol maleate 0.5%, a significant average increase was reported in retinal volumetric blood flow of approximately 13% in normal subjects 1 and 8% in eyes with ocular hypertension. 2 A somewhat similar effect also was observed after 2 weeks of timolol treatment. 3 Carteolol is a relatively new beta-adrenergic blocking agent with partial beta-agonist activity commonly referred to as intrinsic sympathomimetic activity (ISA). Particularly because of its ISA, we were interested in testing whether carteolol could influence retinal volumetric blood flow. Carteolol is the only approved ophthalmic beta blocker in the United States with ISA and enhancement of ocular blood flow could be therapeutically beneficial. The contribution of ISA to beta-blocker therapeutic potential has been studied extensively for cardiovascular hypertension. From th