A pressure and a vision regulation method and device for irrigation of a body cavity (1), in which an inflow liquid pump (2) pressurizes the irrigation liquid in a feed line (13) and an outflow device (3) or an external suction source (20) drains the irrigation liquid from the body cavity (1) through a tubing (16) into a waste container (17). A control unit (4) controls either the inflow liquid pump (2) only or both the inflow liquid pump (2) and the outflow device (3) depending on an inflow irrigation liquid pressure from a pressure sensor (5). The method and the device are combined with a method for detecting blood cells, red blood cells, haemoglobin and/or debris in liquid coming from a surgical site to provide an automatic control and rinsing system with clear vision in the viewing area of the operational site.