Phaco system reduces occlusion

August 15, 2010

Results of a controlled clinical trial show that a software upgrade for performing torsional ultrasound with a proprietary handpiece and phaco system achieves its purpose of minimizing occlusion during phacoemulsification with consequences for improving the safety and efficiency of cataract removal.

Boston-Results of a controlled clinical trial show that a software upgrade for performing torsional ultrasound with a proprietary handpiece and phaco system (OZil and Infiniti Vision System, Alcon Laboratories) achieves its purpose of minimizing occlusion during phacoemulsification with consequences for improving the safety and efficiency of cataract removal, said Robert Cionni, MD, at the annual meeting of the American Society of Cataract and Refractive Surgery.

The study included 118 eyes randomly assigned to two groups to undergo torsional phacoemulsification either with the software enabled at 95% maximum vacuum or without the software. All other surgical settings were standardized, and the two groups were similar with respect to mean cataract grade (~2.2).

Mean volume of balanced salt solution (BSS) used was significantly lower in the software group compared with those operated on without this software, 27.48 versus 35.08 ml, respectively. There was no significant difference between groups in mean cumulative dissipated energy (CDE), Dr. Cionni said.

"There is no doubt that torsional ultrasound is a significant advance in phacoemulsification because it greatly reduces repulsion and improves followability," he said. "Anecdotal impressions from clinical experience indicated [the software upgrade] represented a further improvement. However, the results of this study provide scientific evidence confirming the benefits of the software for reducing occlusions and BSS usage to improve surgical safety and efficiency."

He said that ultrasound energy being delivered during an occlusion is wasted energy and increases the risk for thermal injury. Less time spent in occlusion also means better followability, which, as shown in this study, translates into less BSS usage.

"I am a firm believer that the amount of BSS entering the eye is even more important than the amount of energy used in terms of causing corneal endothelial damage and edema," he said.

For the clinical study, the data on BSS usage and CDE for each case were obtained from the matrix screen of the phaco platform. Determination of the number of occlusive events and their length was based on a "painstakingly detailed" frame-by-frame analysis of high-definition intraoperative video recordings to identify frames when there was full occlusion while in foot position 3, according to Dr. Cionni.

Discussing the rationale for developing the software, Dr. Cionni said that results of multiple studies have documented benefits of torsional phaco compared with longitudinal ultrasound for improving followability and reducing chatter. Nevertheless, many surgeons had been blending torsional with longitudinal ultrasound, especially in denser cataracts and if using a 30° mini-flare tip, with the goal of further improving flow and efficiency.

"However, improper blending, such as using longitudinal ultrasound with torsional when removing less dense cataracts, can actually represent needless use of longitudinal ultrasound, wasting energy and increasing chatter," he said.

By monitoring intraocular conditions so that longitudinal ultrasound is introduced only when needed, the software optimizes fluidic and power management.

FYI

Robert Cionni, MDE-mail: rcionni@theeyeinstitute.com

Dr. Cionni is a consultant, investor, and speaker for Alcon Laboratories and has been actively involved in the development of the software upgrade (OZil IP).