Various arrangements of fluidics systems are disclosed. In one arrangement, an aspiration circuit for a fluidics system is disclosed that selectively controls aspiration. The aspiration circuit comprises an aspiration line operatively connected to a surgical instrument, an aspiration exhaust line operatively connected to a waste receptacle; an aspiration vent line connected at a first end to the aspiration line; and a selectively variable vent valve operatively connected to the aspiration vent line. The variable vent valve may be selectively moved to vary aspiration pressure within the aspiration line. Other fluidics systems are disclosed that include a selectively positionable irrigation valve that may also be incorporated into a fluidics system that includes a variable vent valve.