Determining Optimal Torsional Ultrasound Power for Cataract Surgery With Automatic Longitudinal Pulses at Maximum Vacuum Ex Vivo CECINIO C. RONQUILLO, JR, BRIAN ZAUGG, BRIAN STAGG, KEVIN R. KIRK, ISHA GUPTA, WILLIAM R. BARLOW, JR, JEFF H. PETTEY, AND RANDALL J. OLSON  PURPOSE: To determine the optimal longitudinal po- wer settings for Infiniti OZil Intelligent Phaco (IP) at varying torsional amplitude settings; and to test the hy- pothesis that increasing longitudinal power is more important at lower torsional amplitudes to achieve effi- cient phacoemulsification.  DESIGN: Laboratory investigation.  METHODS: SETTING : John A. Moran Eye Center, Uni- versity of Utah, Salt Lake City, Utah. PROCEDURE : Indi- vidual 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 us- ing a 20 gauge 0.9 mm bent reverse bevel phaco tip at con- stant vacuum (550 mm Hg), aspiration rate (40 mL/min), and bottle height (50 cm). MAIN OUTCOME MEASURE : Com- plete 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 compar- ison of 60% or 80% vs 100% torsional amplitude without longitudinal power showed increased efficiency at 100% (P [ .0004). Increasing longitudinal power to 20% abol- ished the efficiency difference between 80% vs 100% am- plitudes. In contrast, 75% longitudinal power abolished the efficiency difference between 60% vs 100% torsional amplitudes.  CONCLUSIONS: Results suggest that longitudinal po- wer becomes more critical at increasing phacoemulsifica- tion efficiencies at torsional amplitudes less than 100%. Increasing longitudinal power does not further increase efficiency at maximal torsional amplitudes. (Am J Ophthalmol 2014;158:1262–1266. Ó 2014 by Elsevier Inc. All rights reserved.) T HE APPLICATION OF PHACOEMULSIFICATION (phaco) to cataract surgery by Charles Kelman in 1967 ushered in a new era of cataract extraction. 1 The technology remains the standard of care for cataract surgeons in the developed world. Since that time, instru- ments and implants, as well as the programming associated with phaco machines, have improved. The settings allow for custom power modulation and fluidics control, poten- tially improving efficiency, effectiveness, and patient safety. Phacoemulsification uses high-frequency ultrasound to create energy, which is applied with great precision dur- ing surgery. The cataract is essentially removed through aspiration and vacuum forces after the phaco needle breaks the dense material into small enough pieces. Objective studies that compare settings have not been published. Phacoemulsification occurs by a physical jackhammer effect and/or by cavitational break-up of the lens nucleus. 2 A longitudinal, forward-and-backward movement causes physical interaction with the lens nucleus in the forward movement and causes a transient void or cavitational bubbles during the backward movement, which may further break up the lens material. 2 Longitudinal phacoemulsification may be inefficient in that the jack-hammer effect only occurs on the forward motion, which can also cause the lens particle to bounce off the tip (an effect known as chatter), so that no emulsification occurs until the particle is recaptured at the tip. Torsional ultrasound is a more recent approach whereby the needle oscillates such that the tip movement subtends an arc with no longitudinal movement. It is claimed that this shearing action increases efficiency in removing lens nuclei, as movement in both directions is associated with lens nuclei removal. 3 Torsional ultrasound is then less likely than longitudinal phaco alone to result in chatter, which can be both an efficiency and a safety issue. 4 One downside to torsional ultrasound is material blocking the tip so that no material can be aspirated. The system we have tested automatically includes brief pulses of longitudi- nal ultrasound when the maximum vacuum has been reached, in order to clear the tip. The system also allows longitudinal tip action to be included with torsional move- ment in order to maximize the overall efficiency. However, little objective information about how this additional lon- gitudinal motion might be optimized, or if it is even needed to improve efficiency, is available in the literature. Accepted for publication Aug 26, 2014. From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah. Inquiries to Randall J. Olson, John A. Moran Eye Center, University of Utah, 65 Mario Capecchi Drive, Salt Lake City, UT 84132; e-mail: randallj.olson@hsc.utah.edu 1262 0002-9394/$36.00 http://dx.doi.org/10.1016/j.ajo.2014.08.034 Ó 2014 BY ELSEVIER INC.ALL RIGHTS RESERVED.