Removal of cataract debris

A phacoemulsification apparatus, comprising:

• a plurality of actuators configured to vibrate responsively to respective driving signals;
• a needle including an aspiration channel, and configured to be vibrated by the actuators, so as to emulsify a lens of an eye;
• a generator configured to generate at least one of the driving signals responsively to a vibration pattern selected for the needle, the needle being configured to vibrate in accordance with the selected vibration pattern;
• and
• a sensor configured to sense a level of vacuum in the aspiration channel, wherein the generator is configured to alter at least one of the driving signals to transition vibration of the needle from a longitudinal vibration pattern to a helical vibration pattern, responsively to a decrease in the sensed level of vacuum, wherein the longitudinal vibration pattern has a first longitudinal stroke length, and the second helical vibration pattern has a second longitudinal stroke length, which is less than the first longitudinal stroke length.

A phacoemulsification method, comprising:

• generating driving signals responsively to a vibration pattern selected for vibrating a needle;
• vibrating actuators responsively to the driving signals;
• vibrating the needle in accordance with the selected vibration pattern responsively to vibrating of the actuators so as to emulsify a lens of an eye;
• sensing a level of vacuum in an aspiration channel of the needle;
• and
• altering at least one of the driving signals to transition vibration of the needle from a first helical vibration pattern, to a second helical vibration pattern different from the first helical vibration pattern, responsively to a decrease in the sensed level of vacuum.