Background
Autoregulation is defined as the ability of a vascular bed to keep its blood flow constant despite changes in perfusion pressure. While several studies have investigated choroidal blood flow regulation, only few data are available for the optic nerve head (ONH). The aim of the present study was to explore the potential role of a potent vasodilator (nitric oxide) and a potent vasoconstrictor (endothelin-1) in ONH autoregulation.