Optimum on-time duty cycle for a transversal ultrasound machine

Abstract

To evaluate the optimum on-time setting for the most efficient removal of lens fragments using micropulse ultrasound (US) and Ellips FX transversal US in the Whitestar Signature Pro phacoemulsification machine. John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. Experimental study. Porcine lens nuclei were soaked in formalin for 2hours and cut into 2.0mm cubes. The US machine was used with a bent 0.9mm phaco tip and a 30-degree bevel. The off time was set to 6milliseconds (ms) and the on time varied from 4 to 10ms in 1ms increments. Efficiency (time for fragment removal) and chatter (number of times the fragment bounced from the tip) were measured. A linear incremental increase in efficiency was observed between 4ms and 6ms. The most statistically significant efficiency was achieved with an on time of 6ms. On times shorter than 6ms were significantly less efficient (P=.05). Greater on times (7 to 10ms) did not result in a significant difference in efficiency (P=.72), but did appear to have more chatter events when comparing on-time settings of 7 to 10ms with 4 to 6ms (P=.02). With micropulse transversal US, 6ms of on time was as efficient as longer on times. To maximize phacoemulsification efficiency and minimize chatter events, an on time of 6ms is recommended.