Off-Time Duty Cycle Variation in Micropulsed Longitudinal Phacoemulsification

Jensen, Jason

Off-Time Duty Cycle Variation in Micropulsed Longitudinal Phacoemulsification

Monday, April 28, 2014: 9:04 AM

Room 152 (Boston Convention and Exhibition Center)

Jason D. Jensen, University of Utah, Salt Lake City, UT, USA

Kevin Kirk, University of Utah, Salt Lake City, UT, USA

Brian C. Stagg, MD, Moran Eye Center, Salt Lake City, UT, USA

Brian E. Zaugg, MD, University of Utah John A Moran Eye Center, North Salt Lake, Utah, USA

Isha Gupta, University of Utah School of Medicine, Salt Lake City, UT, USA

Mohammed A. Farukhi SLC, UT, USA

Cecinio Ronquillo Jr., PhD, John A. Moran Eye Center, University of Utah, Salt Lake City, UT, USA

William R. Barlow, MD, University of Utah, Salt Lake City, UT, USA

Jeff H. Pettey, MD, Moran Eye Center, Univeristy of Utah, Salt Lake City, UT, USA

Randall J. Olson, MD, Univ. of Utah, Dept of Ophth, Salt Lake City, UT, USA

Narrative Responses:

Purpose
Duty Cycle on/off time efficiency has been discussed between providers of micropulsed ultrasound, but not well researched. This study evaluates the optimal off time for removal of lens fragments using micropulsed ultrasound. Theoretically, ultrasound will be more efficient with a minimal off time, allowing the tip to work longer.

Methods
Porcine lens nuclei were formalin soaked for two hours, then cut into 2mm cubes. We used an AMO Signature machine to do our phaco experimentation. All tips were Microsurgical Technology Inc. 0.9mm, 30-degree bevel. The on time was 7ms and the off time was varied in a 2ms stepwise fashion from 2-20ms. Phacoemulsion efficiency and chatter were measured. An individual lens cube was placed inside a BSS chamber and the time required for phacoemulsification of the cube was recorded. This was repeated 20 times for each experimental group. Averages, standard deviations, and student’s T-tests were performed.

Results
With a constant on time of 7ms the most efficient phacoemulsification was achieved with an off time of 6ms. Off times shorter than 6ms were not statistically different in efficiency (R² = .87, P = .24), although the data points trended towards more efficiency to 6 ms. Greater off times did result in a significant difference in efficiency (R² =.07, P = .0062) with the 18ms off time being the least efficient.

Conclusion
With micropulsed longitudinal ultrasound, 6ms off time was equally as efficient as shorter off times, while longer off times (8-20ms) had decreased efficiency. This is consistent with the theory that longer off times increase phacoemulsification time. Therefore, to maximize phacoemulsification, we recommend an off time setting of 6ms.