Micro-coaxial phaco, torsional ultrasound a perfect marriage, doctor says

February 1, 2008

The combination of torsional ultrasound and micro-coaxial phacoemulsification is ideal for cataract surgery because of the improved efficiency of the ultrasound system and the astigmatically neutral, highly competent 2.2-mm incision through which the highest-quality IOL can be implanted.

Key Points

The smaller incisions, which were made possible by the development of a small-diameter sleeve (Ultrasleeve, Alcon Laboratories) used with a proprietary phaco system (Infiniti, Alcon), have many advantages, he said. Torsional ultrasound, a more recent advance, was introduced approximately 2 years ago, with Dr. Osher as one its early adopters.

The incisional competency of the micro-coaxial technique has been proven in numerous studies, he said, noting that the incisions are also self-sealing. "In an era when surgeons remain so concerned about the risk of infections, this is very reassuring," he said.

One of the primary advantages of micro-coaxial phaco is the fluidics, Dr. Osher said. Initially, concerns existed about getting adequate infusion into the eye with the smaller incision. The smaller sleeve, however, allows about 60% more infusion than a typical 20-gauge irrigating chopper, although the amount is about 25% less than a standard phaco tip.

"To me, superb fluidics are absolutely crucial," Dr. Osher said. The ample infusion through the smaller-sleeve device enables surgeons to maintain a very safe and stable anterior chamber with less leakage, he said.

Another advantage is that the sleeve provides thermoprotection with insulation against wound burns, in addition to the safety of the aspiration bypass system, Dr. Osher said.

A third advantage of the micro-coaxial procedure is that it enables surgeons to implant a full-sized, 6-mm IOL with advanced features through the incision without enlargement. That ability is important because lenses smaller than that size have not been approved in the United States, he added.

Also, studies have shown that the procedure is astigmatically neutral and, therefore, will not diminish the benefits of high-tech lenses such as the toric or aspheric IOLs, which are ushering in a new era of refractive cataract surgery, Dr. Osher said.

Micro-coaxial surgery has little if any learning curve, because the technique for disassembling the nucleus and removing the cortex does not require a change in surgical technique, he said. In addition, it does not require the specialized instruments needed for bimanual microincisional surgery, such as irrigating choppers or capsulorhexis forceps.

Benefits of teamwork

The advantages of micro-coaxial surgery take on even more importance when the technique is paired with torsional ultrasound, which increases the efficiency of ultrasound, Dr. Osher said. "You can further lower your parameters if you choose, because the cutting is so excellent," he added.

"There is no repulsion of nuclear material such as you see with traditional longitudinal ultrasound. There is extreme efficiency, because with traditional ultrasound, the tip is moving backward and forward. The latter is a waste of efficiency and there is evidence that the free radicals created by cavitation are not desirable," Dr. Osher continued.

"The bottom line is that the tip is not working all the time," he said. "But with torsional ultrasound, the motion is from side to side to side to side in an oscillatory fashion, in which the tip is always working. It has terrific advantages in terms of efficiency and in reduction of both turbulence and chatter."

Torsional ultrasound also has thermoprotective effects by reducing the frequency from 42 kHz to 32 kHz. The forward-and-backward movement of traditional ultrasound creates more friction, which in turn generates heat, whereas the side-to-side motion of torsional ultrasound significantly reduces the heat load, Dr. Osher said.