Dipivefrin Reduces Blood Flow in the Ciliary Body in Humans

Abstract

Adrenergic substances are used widely for lowering intraocular pressure in the treatment of glaucoma. The hypothetic mechanisms for lowering the intraocular pressure by adrenergic drugs are decreased blood flow in the ciliary body and direct receptor-related reduction of aqueous humor production. The aim of this study is to measure noninvasively the blood flow in the anterior uvea in humans after topically administered dipivefrin. The blood flow of iris and ciliary body was measured by laser Doppler flowmetry. Laser Doppler flowmetry blood flow and results of the electrocardiogram were simultaneously measured and stored over a period of 3 minutes. In the authors' setup, laser light was projected by a fiber optic transcorneally onto the iris or 2 mm transscerally from the limbus into the ciliary body. For improvement of the signal-to-noise ratio, a statistical averaging procedure was performed by averaging 100 sweeps of 2 seconds of the digitalized laser Doppler flowmetry signals triggered by the R-onset of the electrocardiogram (averaging laser Doppler flowmetry). Using this method, reproducible pulse curves of blood flow of iris and ciliary body were established with systolic maxima and diastolic minima. In a double-blind study design involving 33 young, healthy persons (mean age, 25 +/- 7 years), the effect of topically administered dipivefrin, naphazoline, and NaCl solution (0.9%) on the blood flow of iris and ciliary body was examined. Dipivefrin reduces significantly (average, 49%) the mean blood flow in the ciliary body. Naphazoline and NaCl solution do not change the blood flow in the ciliary body. Dipivefrin, naphazoline, and 0.9% NaCl show no significant effect on the iridal blood flow. The observed data suggest that dipivefrin decreases ciliary body blood flow.