Effects on phacoemulsification efficiency and chatter at variable longitudinal ultrasound settings when combined with constant torsional energy

Abstract

Purpose:To evaluate longitudinal power settings for optimally efficient lens fragment removal, using the Centurion machine.Setting:John A. Moran Eye Center, University of Utah, Salt Lake City, USA.Design:Experimental study.Methods:Porcine lens nuclei were cut into 2.0 mm cubes. Experiments were conducted at 100% torsional power; vacuum set at 500 mm Hg, aspiration 50 mL/min, and intraocular pressure 110 mm Hg. A 20-degree tip with a 30-degree bevel was used. Longitudinal power was tested between 20% and 100%. Efficiency (time for fragment removal) and chatter (the number of times the fragment bounced from the tip) were measured.Results:A linear increase in efficiency was observed from 20% to 100% longitudinal power (R2= 0.9281, slope =-0.0271). An efficiency slope change occurred at 60% power, with the largest incremental change in efficiency between 20% and 60% (R2= 0.9756, slope =-0.0394) and a lesser change between 60% and 100% (R2= 0.9827, slope =-0.0121). Chatter analysis showed minimal events at 20% to 60%, but a significant increase at >80% (P =.005). This increase appeared to be incremental (R2= 0.8929).Conclusions:Increasing longitudinal power, with all other settings constant, increased efficiency. Greatest efficiency gains were observed between 20% and 60%. At 80% and 100%, chatter events increased significantly. With a goal of recommending optimally efficient settings while minimizing excess energy and chatter, adding 60% of longitudinal power to 100% torsional power was shown to be the best setting to increase efficiency and avoid repulsion in these vacuum and aspiration settings.