Methods, systems, and software for controlling infusion pressure, such as during a medical procedure, using systemic blood pressure are described. Systemic blood pressure, such as brachial arm blood pressure or radial artery blood pressure, may be used to estimate central retinal artery blood pressure to estimate critical closing pressure. Further, the disclosure relates to controlling infusion pressure to prevent an increase in intraocular pressure above the estimated critical closing pressure when such is not desired, and, when such is desired, using systemic blood pressure and infusion pressure to control an intentional increase in intraocular pressure above the estimated critical closing pressure to stop intraocular bleeding.