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Combination of technologies helps reduce phaco chatter
Combining continuously variable pulse with torsional phaco allows more efficient emulsification, surgeon says.
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A combination of two new phaco technologies allows surgeons to reduce chatter and maintain better control during phacoemulsification, according to Steve A. Arshinoff, MD, FRCSC.
| Steve A. Arshinoff |
The two technologies — continuously variable pulse and torsional ultrasound — are both available on the Infiniti phacoemulsification unit from Alcon using the OZil handpiece on the Infiniti system. The OZil handpiece can be used for both traditional axial ultrasound, in which the tip moves in and out, and torsional ultrasound, in which the tip oscillates from side to side.
“The new ability to independently set the limits and slopes of phaco amplitude, pulse width and off-time, for both continuously variable axial pulses and for torsional phaco – which can run independently, alternatively or simultaneously – should allow us to almost totally eliminate phaco chatter, making surgery safer and simpler,” said Dr. Arshinoff, speaking at the American Society of Cataract and Refractive Surgery meeting in San Francisco.
Dr. Arshinoff explained that in traditional axial ultrasound, nuclear materials move to and from the phaco tip, a phenomenon known as chatter. Because materials are repelled from the tip, more phaco energy is needed for emulsification. Harder nuclei cause more chatter, he said. Up to 75% of the energy in phaco of hard nuclei can be wasted in chatter, he said.
“Surgeons tend to use more power and more continuous power with harder nuclei, thus making chatter worse. Phaco pulse and phaco burst modes decrease the chatter,” he said.
As chatter is reduced, the turbulence of fluid in the anterior chamber can be reduced by lowering the flow rate, resulting in less endothelial trauma, said Dr. Arshinoff, who is an OSN Cataract Surgery Section Member. Reducing chatter allows more efficient phaco, he said, as well as reductions in the amount of needed vacuum, bottle height and dynamic rise time.
Reduction of chatter also allows surgeons to simplify the number of procedural steps to two, he said: nucleus removal and cortical clean-up. There is no need for programming multiple steps. Dr. Arshinoff said surgeons can simply push the foot pedal down to achieve different results.
Two technologies
With the Infiniti unit, continuously variable pulse and torsional ultrasound can be used separately or together, Dr. Arshinoff said. Results are best when they are used in tandem, he said.
In continuously variable pulse, as the foot pedal is depressed, the ultrasound pulses become shorter but increase in amplitude, and the gap between pulses lengthens.
“As a consequence,” Dr. Arshinoff said, “the energy times time is roughly the same for very hard lenses as it is for soft lenses. We’re just changing the wavefront of the impacts.”
Dr. Arshinoff said the Infiniti allows torsional and axial ultrasound movements to be alternated in a multitude of different combinations. This allows more efficient emulsification, he said.
“The axial pulses smash the nucleus apart, and the OZil pulse is oscillating and eats up the looser pieces,” he said. “The phaco becomes very controlled and very efficient.”
For torsional phaco, Dr. Arshinoff said, the OZil handpiece should be used with the angled Kelman tip.
How they work
Dr. Arshinoff gave examples of how the two technologies can be used together. For instance, he said, the Infiniti can be programmed so that at the top of the foot pedal’s travel, a long axial pulse is followed by a rest, followed by a longer torsional pulse and another rest, and this pattern is repeated over and over. Then, as the pedal is depressed, the pulses become shorter, but the torsional pulse remains longer than the axial pulse.
“You can change the amplitude, pulse width and interval-off time for axial and torsional phaco all independently, resulting in about a thousand different settings,” he said. “And you can actually change it much more than this if you vary the rate of axial-torsional pulse alternations (ie, 1:1, 2:1, 1:2, etc.). The slope of total power increase with foot pedal depression can be changed so that the effective power at total foot pedal depression can be 100%, 150% or 200% greater than, say, at 15% pedal depression, as you alter the waveform of energy delivery for different densities of nuclei. All of this yields an almost infinite possibility to vary the modulations of power delivery, and it can all be done with a mathematical algorithm, with the surgeon being asked only to depress the pedal proportionately to the nuclear density — a rather natural action.”
For more information:
- Steve A. Arshinoff, MD, FRCSC, is a partner at York Finch Eye Associates in Toronto. He can be reached at Suite #316, 2115 Finch Ave., West Toronto, Ontario, Canada M3N 2V6; 416·745·6969; fax: 416·745·6724; e-mail: saaeyes@idirect.com.
- Alcon, maker of the Infiniti and the OZil handpiece, can be reached at 6201 South Freeway, Fort Worth, TX 76134; 817)-293-0450; fax: 817-568-6142; Web site: www.alconlabs.com.
- Erin L. Boyle is an OSN Staff Writer who covers all aspects of ophthalmology.