title: Optimum on-time duty cycle for micropulse technology.
abstract: OBJECTIVE
  To evaluate the optimum on time for the most efficient removal of lens fragments using micropulsed ultrasound (US).
  
  
  METHODS
  John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  Twenty porcine lens nuclei were soaked in formalin for 2 hours and then divided into 2.0 mm cubes. Using an US machine with a 0.9 mm bent and a 30-degree bevel tip, the on time was varied every millisecond (ms) from 2 ms to 10 ms with the off time kept constant at 10 ms. Efficiency (time to lens removal) and chatter (number of lens fragment repulsions from the tip) were determined.
  
  
  RESULTS
  The most efficient phacoemulsification was achieved with an on time of 6 ms. On times shorter than 6 ms were significantly less efficient (R2=.82, P=.04). Greater on times did not result in a significant difference in efficiency (R2=.03, P=.78) but did appear to have more chatter events when comparing 9 to 10 ms with 2 to 8 ms (P<.0001).
  
  
  CONCLUSIONS
  With micropulsed longitudinal US, a 6 ms on time was equally as efficient as longer on times, while shorter on times (2 to 5 ms) had decreased efficiency. At 9 ms and 10 ms on time, significantly more chatter was noted. Therefore, to maximize phacoemulsification, an on-time setting of 6 ms is recommended.
  
  
  BACKGROUND
  No author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Kirk
authors.affiliation: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors.forename: Cecinio
authors.initials: C
authors.lastname: Ronquillo
authors.affiliation: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors.forename: Jason D
authors.initials: JD
authors.lastname: Jensen
authors.affiliation: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Zaugg
authors.affiliation: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors.forename: William R
authors.initials: WR
authors.lastname: Barlow
authors.affiliation: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors.forename: Brian C
authors.initials: BC
authors.lastname: Stagg
authors.affiliation: From the Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.
authors.forename: Jeff H
authors.initials: JH
authors.lastname: Pettey
authors.affiliation: 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.forename: Randall J
authors.initials: RJ
authors.lastname: 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*; D008954:Models, Biological; D061646:Operative Time; D018918:Phacoemulsification; D013552:Swine; D013997:Time Factors
chemical_list: D005404:Fixatives; D005557:Formaldehyde