Torsional phacoemulsification reduces chatter and energy delivered to the eye. It is safer than longitudinal phaco because torsional phaco is associated with a reduced risk of wound burn, less fluid usage, better followability, less turbulence, and less second instrument manipulation.
After using torsional phacoemulsification for cataract removal, it is hard to return to a less-efficient technology, said Robert Cionni, MD, of the Cincinnati Eye Institute.
He explained the biggest problem with longitudinal motion in cataract surgery is that it encourages chatter. "The in-and-out motion of the tip is essentially a repulsive force, so consequently you get more lens chatter. This induces turbulence, reduces followability, increases endothelial insult, and necessitates more second-instrument manipulation," he said, adding that most ophthalmologists must titrate their ultrasound power and settings to compensate for this problem.
"Additionally, standard longitudinal ultrasound tips only cut on the outward movement of the tip. There is no cutting power as it comes back. Over the years, we have been taught that cavitation bubbles are what break up the nucleus, but we now know that this is simply not true," Dr. Cionni said.
"In addition, since there is a repulsive force, we have to modulate the power and adjust the fluidics to keep material at the tip and decrease the risk of chatter and of wound burn. In comparison, torsional phaco is a back-and-forth oscillation, much like [a particular handpiece] (NeoSoniX, Alcon Laboratories) only at ultrasonic speeds. Longitudinal motion is available to use in combination with torsional, but is not required," he said.
The aforementioned handpiece moves at 100 Hz, whereas longitudinal phaco moves at 41,000 Hz and torsional phaco at 32,000 Hz.
"The lower frequency and characteristics of motion results in about a third less heat than longitudinal phaco generates," Dr. Cionni said. "One of the reasons that less heat is generated is the angulation of a curved tip. If the phaco needle is oscillating to and fro, the movement of the shaft is much less than the distance traveled by the tip, so you get a large mechanical force at the tip with very little rotation of the shaft and, therefore, good cutting ability with little heat generated."
Torsional phaco produces smoother flow of material into the tip with smaller pieces. There is very little chatter, enhanced followability, a more stable chamber, and little turbulence.
"It almost feels like cheating as compared with longitudinal phaco," he said.
Dr. Cionni said his favorite tip for torsional phaco is the Kelman-style tapered tip with a standard 2.8-to 3-mm incision because it allows the use of continuous ultrasound without fear of thermal damage at the incision. When using 2.2-mm incisions with microcoaxial phaco, however, he said he prefers the mini-flared Kelman tip, and he modulates power so there is less room for error.
The reduction of delivered energy and chatter that comes with torsional phaco decreases the need for high volumes of balanced salt solution.
"I am a firm believer that it isn't the amount of energy that goes into the eye that causes endothelial cell loss but the amount of turbulent fluid moving through the anterior segment that damages the endothelium," Dr. Cionni said.
He reiterated that torsional phaco means that less energy is delivered into the eye and that safety is greater due to a lower risk of wound burn, less fluid usage, better followability, less turbulence, and less second-instrument manipulation.
"It makes phaco easier because you don't have to manipulate nuclear pieces with the second instrument as much. You can pretty much keep the phaco tip in the center of the pupil and allow pieces to come to you. It is also easy to transition to since you don't need to change your standard techniques. It is very similar to what you already do but it's much, much easier," Dr. Cionni concluded.
Richard Mackool, MD, of the Mackool Eye Institute and Laser Center in Astoria, NY, discussed microcoaxial techniques in cataract surgery. He is a consultant to Alcon Laboratories but vowed to "tell the truth anyway."