A phacoemulsification system, method and computer program product, the system comprising: a phacoemulsification probe having a needle at its distal end, the needle configured to be inserted into an eye of a patient, the probe comprising an ultrasonic transducer; a signal generator, meter, and impedance determination module for determining an impedance between a tip of the needle and an electrode attached to the patient; and a processor, configured to repeatedly: obtain the impedance from the impedance detector; subject to the impedance complying with a condition and the ultrasonic transducer being inactive, toggling the ultrasonic transducer to transmit ultrasonic waves; and subject to the impedance not complying with a condition and the ultrasonic transducer being active, toggling the ultrasonic transducer to stop transmitting ultrasonic waves.