Phaco Technology: What’s Under the Hood — And Why It Matters
BY RENÉ LUTHE, SENIOR ASSOCIATE EDITOR
Ever since Charlie Kelmans fateful visit to a dentist inspired him to adapt an ultrasound teeth-cleaning device for cataract surgery, phacoemulsification has progressed steadily in safety and sophistication with each new iteration of the technology. Modern cataract surgeons and their patients owe a debt to the visionary Dr. Kelman, as well as the innovators who followed in his footsteps.
Rather than resting on their laurels, phaco manufacturers continue to refine their systems for maximum surgeon control. According to cataract surgeons well-versed in latest generation of phaco tech, the new systems provide better fluidics, more controlled power modulations and more efficient removal of lens fragments. They embody the two major milestones that have occurred in recent years: torsional or elliptical phaco, and the trend toward micro-coaxial phaco.
“I think how each of the companies has addressed thermal injury has been huge for surgeons, because they allow us to use smaller incisions,” sums up Ralph Chu, MD, founder and medical director of the Chu Vision Institute in Edina, Minn.
The result of the recent improvements, surgeons say, is better visual outcomes for patients. Read on for the low-down on the features that help the newer phaco systems to fulfill Dr. Kelmans vision.
The Alcon Infiniti Vision System
■ The hand-piece. According to some surgeons, Alcon’s Ozil torsional hand-piece, for nonlongitudinal phaco, alone makes the Infiniti worth the price. Thomas A. Oetting, MD, professor of clinical ophthalmology and residency program director at the University of Iowa, has used earlier versions of the Infiniti and regards the Ozil as a significant improvement. “It doesn’t push pieces [of the dissected cataract] away as much,” he explains. The hand-piece “just makes it a little bit simpler to do some of the newer techniques, or rather, techniques like phaco chop, where you break the cataract into little pieces and simply allow the Ozil to gobble them up.”
Alcon led the way in nonlongitudinal phaco, points out Tal Raviv, MD, of New York Eye and Ear Infirmary. The needle in the torsional hand-piece moves side to side and shears the cataract, rather than simply “jackhammering” it, as is the case in longitudinal phaco.
“As good as that is for decreased heat production, and as efficient as it is because pieces stick to the tip and follow it, nuclear material can sometimes get a little bit occluded at the tip,” Dr. Raviv says. To overcome occlusion, Alcon redesigned the phaco tip. “What they’ve learned is that changing needle designs — for example, using the 45-degree mini-flare tip vs. the 30-degree tapered tip — gives it better cutting power.”
Dr. Chu agrees that the Ozil hand piece makes for a greatly improved surgery. “I think the Ozil tip allows removal of all densities of nuclei very, very well.”
Additionally, the torsional hand piece reduces risk of thermal injury by lessening frictional movements within the incision and lowering the frequency, Alcon says.
Recently, the company has offered the best of both worlds — torsional and longitudinal modes — in the “intelligent phaco” (IP) feature for its phaco system. “Torsional mode by itself is different than longitudinal in that it doesn’t have repulsion. But at the same time, if you don’t include the longitudinal motion in torsional, you lose the pumping effectiveness of that back and forth movement,” explains Steven Dewey, MD, of Colorado Springs.
The Ozil IP software enables the system to detect the vacuum rise in peristaltic mode; as the vacuum is rising, the machine is able to interpret that this means the tip is becoming occluded. “As the vacuum reaches its maximum, it recognizes that it has achieved full occlusion, and then that the oscillating movement isn’t clearing the needle,” Dr. Dewey says. “At that point, it throws in some longitudinal pulses, so it immediately switches without thinking from the torsional to the longitudinal and that way disrupts the clog.” The automation feature makes surgery safer and more efficient, he says. “Basically, this is what we remember as the old occlusion mode, except here the rise in vacuum changes the phaco mode rather than the fluidics parameter.”
■ The pump. The Infiniti features the more traditional flow-based pump, the peristaltic. However, it uses an updated design, with tapered rollers that Alcon says give it “an instantaneous and smooth peristaltic response.”
“With the Infiniti you can set the flow rate and vacuum cut off to have linear control with the foot pedal,” Dr. Oetting says. “As the surgeon pushes further down on the pedal with linear control, you can increase the pump flow rate and increase the vacuum cut off. These linear settings make it more responsive to foot position and, to me, make it act more like the Venturi systems I’ve used.” This avoids the post-occlusion surge previously associated with peristaltic pumps.
The AMO WhiteStar Signature System
■ The hand-piece. The latest WhiteStar transversal ultrasound technology, called Ellips FX, an updated version of its Ellips nonlongitudinal hand piece, provides the highest cutting efficacy with the lowest power use, according to the company.
As Dr. Raviv explains it, “AMO has also improved the cutting power of their next generation Ellips FX. First, they increase the frequency of the needle vibrations; the transversal movement is a blend of side to side and longitudinal motion. And, they also increased the amplitude — it has a longer stroke path so it is able to cut more per vibration, so to speak, and therefore it is more powerful.” Having switched from the first-generation Ellips to the Ellips FX, he says he can see that the cutting efficiency is very smooth without requiring an increase in power settings. “And you still have the followability and the thermal safety that is the benefit of the Ellips nonlongitudinal phaco.”
Dr. Dewey agrees that the advance from the Ellips to the Ellips FX is outstanding. “If a doctor is currently using Sovereign without WhiteStar, and then suddenly gets introduced to the Ellips FX, his jaw is going to hit the floor.”
Dr. Chu appreciates that the Ellips technology allows him to get torsional or elliptical phacoemulsification with a straight needle. “That’s very comforting to me as a surgeon, because it allows you to operate in a shallow chamber more easily. So if you’re using a straight needle, it just makes it a little bit more ergonomically easier inside the eye.”
Phaco System Basics
As a professor of clinical ophthalmology and the residency program director at the University of Iowa, Thomas A. Oetting, MD, believes it is crucial to help students understand the ins and outs of various phaco systems so that they can be successful with whichever one they may be confronted with later in practice.
■ The pump. Prior to the introduction of the Signature line, AMO’s Sovereign was a peristaltic system. Now, however, the Signature offers “fusion fluidics” — peristaltic (flow-based) and Venturi (vacuum-based) pumps in one system.
Surgeons can choose which pump to use, the peristaltic or Venturi, even in the same procedure, Dr. Raviv notes.
“That’s a whole new, novel idea,” Dr. Oetting says. “If you’re doing divide and conquer or you’re sculpting, you might want to use the flow-based pump. If you’re going to do irrigation and aspiration or anterior vitrectomy, you might want to use the Venturi pump. That’s an interesting idea that also in my mind recognizes the fact that Venturi pumps are slightly better for some phases of surgery and the peristaltic pumps are slightly better for other phases.”
Dr. Chu also regards the ability to switch fluidics during the same procedure with just a software setting as crucial. He likes to use the peristaltic mode for removal of the nucleus, then switch to Venturi for removal of cortex and viscoelastic. “Because Venturi doesn’t require full occlusion, you actually get better viscoelastic removal, and I think that’s especially critical for premium lenses.” Excellent cortical cleanup and viscoelastic removal will also be important for coming lens technologies, such as dual-optic accommodating lenses like AMO’s forthcoming Synchrony lens, Dr. Chu points out. “So having that ability to switch between peristaltic and Venturi is critical.”
Additionally, with the Ellips FX 2.0 software, there is more setting control for the fluidics. Combined with the FX hand piece, the fluidics greatly enhance the Signature’s ability to remove nuclear material, according to Dr. Dewey. “Especially denser nuclear material.”
The benefits of these innovations, he says, include less chatter, less turbulence, greater chamber stability — and clearer corneas. “We have the confidence to tackle those tougher cataracts and give them the same early results postoperatively that the patients with softer cataracts will achieve.”
■ Micro-incisional phaco too. Proponents of the Signature note that it offers flexibility in incision size, an important consideration for cataract practices that use premium IOLs.
“In a practice like mine, incision size is important because we are trying to minimize astigmatism induction, but there is the component of putting in a premium lens,” Dr. Chu explains. When implanting patients with the Crystalens IOL, for example, he must make a 2.75-mm incision. The Signature allows for that, he says, but because it has the WhiteStar technology, it also allows the surgeon to perform bimanual, micro-incisional, sleeveless surgery.
The Bausch+Lomb Stellaris Vision Enhancement System
■ The hand-piece. The Stellaris’s lightweight titanium handpiece combines low frequency and the company’s “Attune” energy management system, which includes an advanced waveform modulation that allows the user to select variable duration and depth, to focus emulsification energy into the lens to enable a very low-energy procedure. “I think B+L really worked hard to minimize if not eliminate the issue of thermal injury,” Dr. Chu says.
The hand-piece is ergonomically designed to avoid tiring the surgeon’s hand, the company says.
■ The pump. The Stellaris also offers both peristaltic and vacuum fluidics. Surgeons can intraoperatively choose between flow- or vacuum-response, according to task and their own preference, B+L says. Moreover, the vacuum mode does not require an external compressed gas line, an advantage that Dr. Oetting appreciates. “It gives you more flexibility as to where the machine is in the room, and it’s one more line you don’t have that people could trip over,” he says. Further, not all ORs have the ability to provide compressed gas.
■ The foot pedal. The Stellaris’ dual-linear foot pedal, which provides two directions of control, is wireless, a feature that Dr. Oetting particularly appreciates. “It sounds trivial, but it’s really a nice safety feature, so people don’t have to worry about tripping on the foot pedal line,” he explains. It also allows the operator to be more comfortable as the wireless pedal can be positioned wherever it is most convenient. The two directions of control provided by the foot pedal mean that it can not only move vertically, like that that of other phaco systems, but can also move horizontally, allowing the pedal to be set up in many configurations, such as irrigation and aspiration on the vertical and phaco power on the horizontal, according to B+L.
■ The whole micro-incisional enchilada. “This is where B+L’s Stellaris unit really led the way with micro-coaxial phaco by having the 1.8-mm surgery,” Dr. Raviv notes. The benefits of a sub 2-mm incision include a reduction in surgically induced astigmatism, a reduction in endothelial cell loss and increased visual recovery. Dr. Chu points out that the Stellaris is the only system that also offers a micro-incisional IOL as well, the Akreos AO. “So combining their phaco system with that lens you can actually have the entire micro-incisional package,” he says.
The Stellaris also of course supports standard small-incision coaxial phaco.
As a teacher, Dr. Oetting finds the Stellaris’s intuitive interface a very helpful improvement over its predecessor in instructing residents in phacoemulsification. “From the point of view of teaching the residents the settings for each phase of surgery and most importantly, teaching the residents how to change settings when needed, the Stellaris user interface is an upgrade from the Millennium because it’s just easier to understand what’s going on.”
While each phaco system has its nuances that might lead an individual surgeon to prefer one over the others, these clinicians affirm that all represent pronounced advancements over their recent predecessors.
“They’re all at such high levels at this point that they all achieve excellent results, excellent visual acuity,” Dr. Raviv says. Each, he says, feature advanced fluidic sensors to minimize complications such as post-occlusion surge.
Thermal injury is now much less of a problem with these systems, Dr. Chu says, because each allows for smaller incisions. All that’s left is to try them out so you can find the system that suits you best. OM