Ocular hemodynamic effects of nitrovasodilators in healthy subjects

Abstract

Abstract Purpose: Previous studies on the ocular hemodynamic effects of nitrates showed partially contradicting results. The aim of the present study was to investigate the effect of nitrovasodilators on choroidal and optic nerve head (ONH) blood flow. Methods: The study was performed in a randomized, placebo‐controlled, double masked, 4‐way crossover design in 12 healthy male subjects. Nitroglycerine, isosorbide dinitrate or sodium nitroprusside were administered intravenously in stepwise increasing doses on different study days. Physiologic saline solution was used as placebo control. To assess choroidal and ONH microcirculation, laser Doppler flowmetry measurements were performed. Laser interferometric measurements of fundus pulsation were used to assess pulsatile choroidal and ONH blood flow. Ocular perfusion pressure (OPP) was calculated as OPP=2/3MAP‐IOP. Thereafter a parameter of vascular resistance (R) for each measured blood flow parameter (BF) was calculated as R~OPP/BF. Results: Placebo administration did not change any of the measured parameters. We observed small but significant reduction of IOP during the infusion of sodium nitroprusside. The pulsatile choroidal blood flow decreased significantly during the infusion of isosorbide dinitrate (–8.1%) and sodium nitroprusside (–4.3%). The pulsatile ONH blood flow decreased significantly only during the infusion of sodium nitroprusside (–5.7%). In addition, we observed a significant reduction of all calculated parameters of vascular resistance during the infusion of each nitrovasodilator (maximal decrease: –16% to –29%). Conclusions: An intravenous infusion of nitroglycerine, isosorbide dinitrate or sodium nitroprusside caused a significant reduction of vascular resistance in the ONH and the choroid.