DIPIVEFRIN REDUCES BLOOD-FLOW IN THE CILIARY BODY IN HUMANS

Purpose: Adrenergic substances are used widely for lowering intraocula r pressure in the treatment of glaucoma. The hypothetic mechanisms for lowering the intraocular pressure by adrenergic drugs are decreased b lood flow in the ciliary body and direct receptor-related reduction of aqueous humor production. The aim of this study is to measure noninva sively the blood flow in the anterior uvea in humans after topically a dministered dipivefrin. Method: The blood flow of iris and ciliary bod y was measured by laser Doppler flowmetry. Laser Doppler flowmetry blo od flow and results of the electrocardiogram were simultaneously measu red and stored over a period of 3 minutes. In the authors' setup, lase r light was projected by a fiber optic transcorneally onto the iris or 2 mm transscerally from the limbus into the ciliary body. For improve ment of the signal-to-noise ratio, a statistical averaging procedure w as performed by averaging 100 sweeps of 2 seconds of the digitalized l aser Doppler flowmetry signals triggered by the R-onset of the electro cardiogram (averaging laser Doppler flowmetry). Using this method, rep roducible pulse curves of blood flow of iris and ciliary body were est ablished with systolic maxima and diastolic minima. In a double-blind study design involving 33 young, healthy persons (mean age, 25 +/- 7 y ears), the effect of topically administered dipivefrin, naphazoline, a nd NaCl solution (0.9%) on the blood flow of iris and ciliary body was examined. Results: Dipivefrin reduces significantly (average, 49%) th e mean blood flow in the ciliary body. Naphazoline and NaCl solution d o not change the blood flow in the ciliary body. Dipivefrin, naphazoli ne, and 0.9% NaCl show no significant effect on the iridal blood flow. Conclusion: The observed data suggest that dipivefrin decreases cilia ry body blood flow.