Tapered structure in a phacoemulsification device for node placement

Abstract

Disclosed is a surgical instrument directed to phacoemulsification for cataract eye surgery. The instrument generally includes a hollow titanium needle extending from a vibration generating handpiece. Together, the hollow needle and handpiece form an aspiration pathway to suck cataractous debris from an eye. A piezoelectric transducer in the handpiece generates both high and low ultrasonic frequency vibrations that rings the needle. The low frequency produces a node-free standing wave along the needle and the high frequency produces a standing wave along the needle with a node of minimum amplitude along the needle. Both frequencies produce a high anti-node at the needle's tip. The low frequency causes higher cavitation for emulsifying the cataract and the high frequency facilitates fragmentation of the cataract with a low heat portion of the needle at the eye incision point. The placement of the node along the needle can be tailored by way of a tapered section in a step horn region of the handpiece.