Bumanual microincision phaco 'ready for prime time'

April 15, 2005

Dorado Beach, Puerto Rico—Bimanual microincision phacoemulsification is ready for prime time and expected to have an even brighter future, according to William W. Culbertson, MD, at the Current Concepts in Ophthalmology meeting.

"There are critics who say there is no role for bimanual microincision phaco because of the need to enlarge the incision for IOL insertion. However, it is really a superior method that facilitates cataract surgery in general. Its benefits are not just about incision size, but it will have added value once microincision IOLs become available in the United States," said Dr. Culbertson, professor of ophthalmology, Bascom Palmer Eye Institute, University of Miami. He spoke during the meeting, sponsored by Johns Hopkins University School of Medicine, Baltimore, and Ophthalmology Times.

He defined bimanual microincision phaco as a procedure in which phacoemulsification and cortical aspiration are performed through two sub-2-mm incisions with a sleeveless phaco needle and a separated infusion source.

Improved fluidics The advantages of SIMPLE are several. One important benefit is improved fluidics. Because it separates infusion and aspiration, infusion flow resistance of aspiration flow is eliminated. Thus, aspiration flow rates and vacuum settings can be lowered and the infusion can be better used to maneuver the lens material toward the phaco needle.

In addition, because the irrigation and aspiration ports are interchangeable, removal of subincisional cortex is facilitated and lens material removal in difficult cases can be performed with added safety. Once smaller IOLs become available, the sub-2-mm incisions should minimize the risk of induced astigmatism. Meanwhile, they offer enhanced safety by providing a better seal, Dr. Culbertson said.

The ability to perform bimanual microincision phaco depends on the availability of cooler phaco and an adequate, separate infusion source. Developments in ultrasound power modulation software and a recent market explosion of microincision instrumentation have allowed this technique to take its place in the cataract surgeon's armamentarium, Dr. Culbertson said.

When performing bimanual microincision phaco, Dr. Culbertson uses Sovereign with WhiteStar (AMO). He explained WhiteStar is hyperpulse software that allows the surgeon to design a pattern of short "on" times and longer "off" times, which result in a cooler phaco needle and the same or improved surgical efficiency. Similar technology is available from other phaco system manufacturers.

"The very short micropulses create more effective transient phaco energy because there is less repelling force of the nucleus with each 'on' pulse. As a result, total phaco time and energy utilization are reduced," he said.

Prevention of excess heating For further prevention of excess heating of the sleeveless phaco tip, Dr. Culbertson aims to have some infusion fluid flow back up the needle during aspiration and to have some minor fluid leakage at the wound site.

For infusion, surgeons can choose a two-port system with an infusion chopper or a three-port chamber maintainer system.

"The latter method, which is favored by Richard Lindstrom, MD, has advantages for maintaining the anterior chamber throughout the procedure and preventing anterior displacement of the posterior capsule," Dr. Culbertson noted.

To assure adequate sideport infusion, Dr. Culbertson hangs the infusion bottle higher when performing bimanual microincision surgery relative to conventional coaxial phaco. However, he noted special attention also needs to be paid to selection of an infusion chopper. The instrument should afford a flow rate of at least 50 ml/min and be thin-walled and front-opening. Dr. Culbertson uses a 19-gauge instrument that he prefers because it provides 30% more open area than a 20-gauge infusion needle.