Software optimizes torsional ultrasound

March 15, 2010

The safety and efficacy of cataract removal using torsional ultrasound with a proprietary handpiece and phacoemulsification system have been raised to a higher level by a recent software upgrade, according to one expert.

Key Points

Houston-The safety and efficiency of cataract removal using torsional ultrasound with a proprietary handpiece and phacoemulsification system (OZil and Infiniti Vision System, Alcon Laboratories) have both been raised to an even higher level by a recent software upgrade (OZil Intelligent Phaco [OZil IP], Alcon), according to Robert P. Lehmann, MD.

"I considered torsional ultrasound with [the handpiece] the most tremendous advance I'd seen in cataract surgery since I first learned phacoemulsification during my residency [more than] 30 years ago," said Dr. Lehmann, clinical associate professor of ophthalmology, Baylor College of Medicine, Houston. "However, to maximize torsional ultrasound, it is important to keep lens material in the shearing plane of the phaco tip."

When working in foot pedal position 3, the software upgrade tracks the aspiration flow rate and vacuum and determines when the phaco tip is near occlusion. It then acts "intelligently," adapting the energy delivery to provide small amounts of repulsive longitudinal ultrasound so that the lens material is repositioned into the shearing plane to maintain optimal emulsification efficiency while preventing occlusion.

"The main benefit of [the handpiece] for improving phaco efficiency has been its side-to-side shearing action that means the nucleus is constantly being emulsified," Dr. Lehmann said. "[The software upgrade] assures that the nuclear material is always positioned for achieving this shearing efficiency."

Since full occlusion is rarely reached, the phaco system's peristaltic pump continues to deliver nuclear material to the phaco tip, and pressure fluctuations also are reduced, providing improved anterior chamber stability.

"By maintaining optimal fluidics and continuous emulsification, the intraocular environment improves such that nuclear fragments are continually drawn to the phaco tip," he said. "[The software upgrade] essentially takes over as the second instrument in the eye, promoting a self-feeding followability of nuclear pieces directly to the phaco tip."

The benefits of the software upgrade are evidenced clinically by the presence of clearer corneas on postoperative day 1 and earlier visual recovery, with excellent visual acuity results achieved as early as the afternoon of surgery. Furthermore, although the upgrade improves efficiency for the very easy and average cataract surgery cases, it really has its greatest impact for facilitating a safe and efficient procedure in eyes with very hard nuclei, he said.

Fracture technique

Dr. Lehmann explained that his surgical approach involves a fracture technique. After completing hydrodissection (hydrodelineation is performed only for very soft nuclei), Dr. Lehmann first divides the nucleus into halves by creating a deep groove. After rotating the lens 90°, he uses the phaco tip to crack the first hemisphere in half in a technique that is similar to a quick chop but with the use of some grooving.

The benefit of the software upgrade is particularly evidenced after the first two quarters of the nucleus are removed because it is then possible to remove the remaining half of the nucleus safely and efficiently without any need for further division.

"With [the software upgrade], the remaining nucleus stays at the phaco tip, and I can complete the removal of a dense cataract with minimal ultrasonic energy and reduced risk for occlusion to provide the patient with a better outcome," he said.

"I regularly hear from colleagues who have had the same surgeon- and patient-pleasing experience with this technology," Dr. Lehmann added.

FYI

Robert P. Lehmann, MD
E-mail: doctorlehmann@me.com

Dr. Lehmann is a consultant to Alcon Laboratories. The enhanced software now is available on all newly purchased phaco systems (Infiniti, Alcon) and also is available as an upgrade for equipment in the field.