A phacoemulsification system for operating a surgical handpiece having a handpiece; an irrigation fluid source for supplying irrigation fluid to the eye; an aspiration source coupled to the handpiece in order to aspirate the irrigation fluid from the eye through the handpiece; and a controller for controlling a vacuum in the handpiece, the controller comprising: a sensor for sensing the vacuum in the handpiece; an occlusion parameter, the occlusion parameter being a vacuum level corresponding to an occlusion of the handpiece or a flow rate corresponding to an occlusion of the handpiece; a maximum allowable vacuum level in the handpiece, the maximum allowable vacuum level having at least a first predetermined level; and a trigger value that is set based in part on the occlusion parameter.