The debate over Kelman phaco tips versus balanced phaco tips has taken a recess. A head-to-head study found the newer balanced tip is nearly 30% more efficient than the more familiar Kelman tip over the entire range of operating power, said Brian E. Zaugg, MD.
“There have not been many objective studies comparing phaco tips,” said Dr. Zaugg, assistant professor of ophthalmology, Moran Eye Center, Salt Lake City.
“What we have seen is that a balanced tip has more movement and an increased amount of work being applied to the cataract at a given phaco power,” he said. “This study confirms the general clinical feeling that the balanced tip is more efficient.”
Dr. Zaugg directed an in vitro study comparing the standard Kelman tip with the newer torsional tip (OZil Intrepid Balanced tip, Alcon Laboratories). The study was conceived, led, and analyzed by Tyler D. Boulter, BS, medical student at Texas A&M University, College Park, TX.
Longitudinal, torsional ultrasound
Traditional cataract removal by longitudinal ultrasound uses a forward-and-backward tip motion to produce the physical interaction required for phacoemulsification, Dr. Zaugg noted.
Longitudinal ultrasound is less than optimally efficient because the lens particle can bounce off the tip during the forward motion, the effect commonly called chatter. The backward motion of the tip also creates a transient void during which no energy is transferred to the cataract.
Torsional ultrasound oscillates the tip in a side-to-side motion, with the tip subtending an arc. This motion induces a sheering action that is claimed to be more efficient because the tip remains in contact with lens nuclei throughout the arc and produces more constant emulsification. The lack of forward motion is said to result in less chatter, which could also improve efficiency and patient safety.
In what may be the first head-to-head trial of the two tips, researchers fixed porcine lenses in formalin and cut the lenses into 2.0-mm cubes to simulate brunescent human nuclei. These extremely dense nuclei require more effort, more phaco energy, and more time to treat successfully than the typical cataract, Dr. Zaugg noted.
The individual lens cubes were phacoemulsified (Centurion Vision System, Alcon) using a standard 30° Kelman 0.9-mm tip and the OZil Torsional Balanced tip at the same settings: a constant vacuum (500 mm Hg), constant aspiration rate (50 mL/min) and constant IOP (50 mm Hg) at 60% and 100% torsional amplitude. Each torsional setting included longitudinal power settings of 0%, 25%, 50%, 75% and 100%. A total of 20 runs were conducted at each setting.
Efficiency was measured as the time needed for the complete emulsification and removal of each lens cube. Chatter events for each trial were also recorded.
Results supported the general clinical impression that balanced tips are more efficient. While the precise differences in tip efficiency varied by power applied, the balanced tip removed lens fragments in an average of 29% less time than the Kelman tip at the same power setting (p < 0.0001), Dr. Zaugg noted.
In addition, 100% torsional power averaged 45% faster (p = 0.0028) compared with 60% power regardless of the longitudinal power used.
Chatter was minimal at all longitudinal power settings below 75% and increased with higher longitudinal power. There was a significant increase in chatter at 100% longitudinal power compared with 75% regardless of the torsional power applied (p < 0.0001). The balanced tip showed significantly more chatter than the Kelman tip with 100% longitudinal power at both 60% torsional power (p < 0.0001) and 100% torsional power (p = 0.0022).
“My sense is that more ophthalmologists are moving to the balanced tip,” Dr. Zaugg said.
“These findings help validate the general clinical opinion that the balanced tip is more efficient and help explain the mechanic,” he said. “We still have a couple of surgeons who use Kelman tips. Tip selection can be a preference for how one instrument feels and responds over the efficiency of the tool.”
Data also suggest the balanced tip may provide patient safety benefits. More efficient phacoemulsification should translate into shorter operating times and less energy being applied to the eye.
“Being more efficient in the eye is a constant goal,” Dr. Zaugg said. “We can achieve greater efficiency by adding the balanced tip to our armamentarium.”