title: Determining optimal ultrasound off time with micropulse longitudinal phacoemulsification.
abstract: OBJECTIVE
  To evaluate the optimum off time for the most efficient removal of lens fragments using micropulse ultrasound (US).
  
  
  METHODS
  John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  Porcine lens nuclei were soaked in formalin for 2 hours and then cut into 2.0 mm cubes using the Signature US machine with a bent 0.9 mm phaco tip with a 30-degree bevel. The on time was 7 milliseconds (ms), and the off time was varied from 2 to 20 ms in 2 ms steps. Phacoemulsification efficiency (time for fragment removal) and chatter (number of times the fragment bounced from the tip) were measured.
  
  
  RESULTS
  A nonsignificant linear increase in efficiency was observed with 2 to 6 ms of off time (R(2) = .87, P = .24). A significant linear decrease in efficiency was observed with 6 to 20 ms (R(2) = .74, P = .006).
  
  
  CONCLUSIONS
  With micropulse longitudinal US, 6 to 7 ms of off time was as efficient as shorter off times; longer off times (8 to 20 ms) showed decreased efficiency. Chatter was minimal and statistically similar throughout. To maximize phacoemulsification US efficiency, an off-time setting of 6 ms is recommended.
  
  
  BACKGROUND
  No author has a financial or proprietary interest in any material or method mentioned.
authors: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors: Jason D
authors: JD
authors: Jensen
authors: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors: Kevin R
authors: KR
authors: Kirk
authors: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors: Isha
authors: I
authors: Gupta
authors: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors: Cecinio
authors: C
authors: Ronquillo
authors: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors: M Aabid
authors: MA
authors: Farukhi
authors: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors: Brian C
authors: BC
authors: Stagg
authors: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors: Jeff H
authors: JH
authors: Pettey
authors: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. Electronic address: randallj.olson@hsc.utah.edu.
authors: Randall J
authors: RJ
authors: Olson
mesh_terms: D000818:Animals; D005404:Fixatives / Q000494:pharmacology; D005557:Formaldehyde / Q000494:pharmacology; D019220:High-Energy Shock Waves; D007908:Lens, Crystalline / Q000187:drug effects / Q000601:surgery*; D018918:Phacoemulsification / Q000379:methods*; D013552:Swine; D013997:Time Factors
chemical_list: D005404:Fixatives; D005557:Formaldehyde