Regulation of Optic Nerve Head Blood Flow During Combined Changes in Intraocular Pressure and Arterial Blood Pressure

Autoregulation is defined as the ability of a vascular bed to adapt its vascular resistance to changes in perfusion pressure. In the eye, several studies have reported that retinal blood flow is autoregulated over a wide range of ocular perfusion pressures. In the optic nerve head only few data are available. Large scale studies have shown that reduced ocular perfusion pressure is an important risk factor for the prevalence, the incidence and the progression of primary open angle glaucoma. Former studies that investigated ocular blood flow autoregulation only measured choroidal blood flow. For the optic nerve head only few data are available, although it seems likely that it underlies similar autoregulatory mechanisms. The primary goal of the present study is to gain more insight into these phenomena in humans. The present study aims to investigate the pressure/flow relationship as a measure for optic nerve head autoregulation during combined changes of intraocular pressure and arterial pressure. Intraocular pressure will be increased by the use of a suction cup technique, mean arterial pressure will be increased by squatting. During the whole procedure, optic nerve head blood flow will be measured continuously.