A vitrectomy apparatus is provided, including a pressure source, a cut valve connected to the pressure source, the cut valve configured to be turned on and off to provide pressure to selectively extend and retract a vitrectomy cutting device, a sensor configured to sense pressure provided from the cut valve, and a controller configured to control operation of the cut valve based on pressure sensed by the sensor. The controller is configured to monitor an amount of dwell time the vitrectomy cutting device remains open and monitor aspiration rate, and control a rate of material processed by the vitrectomy cutting device based on amount of dwell time and aspiration rate.