Individual ONH blood flow patterns during changes in perfusion pressure

Abstract

AbstractPurpose Abnormal optic nerve head (ONH) blood flow autoregulation has been implemented in the pathogenesis of glaucoma since decades. In fact, however, the regulation of ONH blood flow is poorly characterized and the mechanisms of autoregulation remain obscure.Methods Several studies were performed to investigate the behavior of ONH blood flow during changes in perfusion pressure in healthy subjects. In all these studies laser Doppler flowmetry was used to measure ONH blood flow. Interventions included squatting and handgripping to increase ocular perfusion pressure and use of a sclera suction cup to reduce ocular perfusion pressure.Results During both an increase and a decrease in perfusion pressure the ONH shows some autoregulatory capacity. Data during combined change in arterial pressure and venous pressure indicate that ONH blood flow is not only dependent on the level of perfusion pressure but also on the absolute levels of pressures in the arterial and venous tree. In addition, there is a wide inter‐individual variability in the responses. In some subjects a temporal reduction in ocular perfusion pressure is associated with a pronounced decrease in ONH blood flow.Conclusion Regulation of ONH blood flow is more complex than previously thought. Some subjects show pronounced ischemia during fluctuations in ocular perfusion pressure. Whether this pre‐disposes to ONH disease remains unclear.