An aspiration circuit for a fluidics system (11) for selectively controlling aspiration, including an aspiration line (52) operatively connected to a surgical instrument； an aspiration pump to create an aspiration flow in the aspiration line； an aspiration exhaust line (54) operatively connected to the aspiration pump on one end and to a waste receptacle (58) on an opposing end； an aspiration vent line (60) connected at a first end to the aspiration line between the aspiration pump and the surgical instrument； and a selectively variable vent valve (62) operatively connected to the aspiration vent line (60), wherein the variable vent valve (62) may be selectively moved to selectively change aspiration pressure within the aspiration line； The aspiration circuit further includes an irrigation line (50) operatively connected to the surgical instrument (42)； an irrigation pressure sensor (475) and an actuator, the irrigation pressure sensor being positioned to detect irrigation pressure in the irrigation line and the actuator being operatively connected to the vent valve； wherein the irrigation pressure sensor (475) and the actuator are connected to a controller, and wherein the controller (40) is operative to initiate the actuator to move the vent valve in response to pressure detected by the irrigation pressure sensor to vary the aspiration pressure within the aspiration line (52).
