Software upgrade advances torsional ultrasound

November 15, 2009

A phacoemulsification software upgrade further enhances safety, efficiency, and control for surgeons performing torsional ultrasound with proprietary handpiece and phaco system.

The software monitors intraocular conditions to maintain optimal positioning of nuclear material at the tip for maximal shearing efficiency and to avert tip occlusions that can lead to surge. The result is optimized fluidic and power management so that lens emulsification is completed with the least amount of energy necessary and complete chamber stability, regardless of cataract density.

"Thanks to its benefits for improving followability and reducing chatter, . . . torsional ultrasound has been such a tremendous advance in improving phaco efficiency that I would not want to do surgery without it. [The software] has a comparable impact for enhancing the procedure," said Dr. Cionni, medical director, Eye Institute of Utah, Salt Lake City, and former medical director, Cincinnati Eye Institute, Cincinnati.

The idea for creating the software was based on surgical experience with the handpiece in eyes with denser cataracts where the lens emulsification could sometimes slow down or an internal tip occlusion could occur. To limit or resolve these situations, surgeons were already using torsional ultrasound blended with longitudinal ultrasound. Although successful, this strategy was accompanied by unnecessary use of additional longitudinal ultrasound in many cases and the potential for unneeded extra chatter.

"[The software upgrade] adds bursts of longitudinal ultrasound only when needed and acts as an artificial intelligence system, working in the background without the surgeon's conscious input," Dr. Cionni said.

Machine settings

Using the software upgrade, surgeons can maintain their usual machine settings for torsional ultrasound but without having to alter them according to cataract grade. Then they set three parameters for the software: 1) the vacuum level when the longitudinal pulses should begin, 2) the power of the longitudinal ultrasound relative to the torsional amplitude, and 3) the width of the longitudinal ultrasound pulses.

Dr. Cionni said he typically operates using 350 mm Hg as his maximum vacuum setting. He sets the software so that the longitudinal ultrasound bursts are introduced when vacuum reaches 95% of 350 mm Hg, at a 10-millisecond pulse width, and at 100% power relative to the torsional amplitude.

"If the percentage of longitudinal power relative to torsional amplitude is set at 100% and the [handpiece] amplitude is at 80% when the threshold vacuum level is reached, longitudinal ultrasound will kick in at 80% power," Dr. Cionni said. "If the longitudinal power was preset at 50%, the longitudinal ultrasound would operate at 40% power."

Proving the principle

Dr. Cionni said he has launched a comparative study to verify his clinical impressions about the benefits of the software, and the preliminary results are strongly positive. In the study, 200 consecutive patients are randomly assigned to undergo cataract surgery in alternating rooms, one where the software is enabled and a second where the software is turned off. Otherwise, all machine settings, techniques, and equipment are the same in both groups.

The endpoints being collected for the study are cumulative dissipated energy (CDE), volume of balanced salt solution used, and occlusion time during each case as identified via frame-by-frame analysis of the overlay designation. Results will be compared between surgical groups for all eyes pooled and based on cataract grade.

"With one-fourth of the planned population enrolled, the overall data show that operating with [the software] significantly minimizes fluid use and CDE and markedly reduces occlusion time," Dr. Cionni said. "However, it is important to point out that occlusion time is already extremely low using [the handpiece] without the new software upgrade, indicating that with torsional ultrasound, there is always fluid moving into the tip to improve efficiency and decrease the risk for any thermal injury to the wound."