The invention relates to a handpiece for the phacoemulsification of an eye lens, having a needle with an aspiration line arranged therein for transporting an aspiration fluid and at least one drive element for generating a longitudinal wave, wherein the drive element is arranged in such a way that the longitudinal wave can be coupled directly into the aspiration fluid. A positive force expander for an adjustable occlusion device is also disclosed. The tibial guide includes a vertical resection channel having a variable width preoperatively configured for guiding a vertical resection through the proximal portion of the tibial bone.