Determining Optimal Torsional Ultrasound Power for Cataract Surgery With Automatic Longitudinal Pulses at Maximum Vacuum Ex Vivo

PURPOSE: To determine the optimal longitudinal power settings for Infiniti OZil Intelligent Phaco (IP) at varying torsional amplitude settings; and to test the hypothesis that increasing longitudinal power is more important at lower torsional amplitudes to achieve efficient phacoemulsification. DESIGN: Laboratory investigation. METHODS: SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah. PROCEDURE: Individual porcine nuclei were fixed in formalin, then cut into 2.0 mm cubes. Lens cube phacoemulsification was done using OZil IP at 60%, 80%, and 100% torsional amplitude with 0%, 10%, 20%, 30%, 50%, 75%, or 100% longitudinal power. All experiments were done using a 20 gauge 0.9 mm bent reverse bevel phaco tip at constant vacuum (550 mm Hg), aspiration rate (40 mL/min), and bottle height (50 cm). MAIN OUTCOME MEASURE: Complete lens particle phacoemulsification (efficiency). RESULTS: Linear regression analysis showed a significant increase in efficiency with increasing longitudinal power at 60% torsional amplitude (R-2 = 0.7269,P = .01) and 80% torsional amplitude (R-2 = 0.6995, P = .02) but not at 100% amplitude (R-2 = 0.3053, P = .2). Baseline comparison of 60% or 80% vs 100% torsional amplitude without longitudinal power showed increased efficiency at 100% (P = .0004). Increasing longitudinal power to 20% abolished the efficiency difference between 80% vs 100% amplitudes. In contrast, 75% longitudinal power abolished the efficiency difference between 60% vs 100% torsional amplitudes. CONCLUSIONS: Results suggest that longitudinal power becomes more critical at increasing phacoemulsification efficiencies at torsional amplitudes less than 100%. Increasing longitudinal power does not further increase efficiency at maximal torsional amplitudes. (C) 2014 by Elsevier Inc. All rights reserved.