In recent years, advance-ments in technology have improved the efficiency and safety of phacoemulsification. All three of the currently available systems from the major American manufacturers offer their own unique benefits. The current trend is toward microincision cataract surgery, which offers the benefits of reduced astigmatism, improved intraoperative safety and an improved rate of wound sealing.
Intrepid Micro-Coaxial System
The first real advance toward safer and more efficient phaco in the current generation of machines was the Infiniti System (Alcon). The Infiniti can use a combination of longitudinal and torsional ultrasound, which has several benefits. One of the disadvantages of longitudinal ultrasound is that, because of its back-and-forth motion, chatter and repulsional forces increase at higher power settings. "It has a jackhammer effect and causes pieces of nucleus to move away," says Lisa Arbisser, MD, who is in private practice in
Torsional has several advantages over longitudinal ultrasound. "One of the main benefits is better followability because pieces of nucleus are not pushed away," Dr. Arbisser says. "Additionally, torsional reduces thermal damage because there isn't the friction at the wound site from something moving back and forth. Rather, because it twists basically at the tip, there is very little friction at the incision so it reduces thermal production of heat by about two-thirds. This offers added protection from wound burn, although there is no system in the world that can't burn if there is no flow."
She notes that torsional is not as efficient as longitudinal for chopping the nucleus. Dr. Arbisser uses longitudinal for the disassembly phase and torsional for removal of nucleus. To avoid clogging when removing very dense nuclei, Dr. Arbisser uses a few microbursts of longitudinal with the torsional.
The system is also compatible with microincisional surgery (2.4-mm incision or less). The Intrepid Micro-Coaxial System uses both the Infiniti Vision System and the OZil Torsional handpiece (Alcon). "The Infiniti unit is the only unit that I know of that has a fully integrated line of equipment and instruments specifically designed for 2.2- to 2.4-mm surgery," says Terry Kim, MD, associate professor of Ophthalmology, Cornea and Refractive Surgery at
While OZil is not new, new tips are available that are specifically designed for 2.2-mm incisions. Dr. Kim uses a 45-degree beveled mini-flared Kelman tip that works extremely well for 2.2-mm incisions. He has found this tip to be more efficient than the older tips with a larger 2.8-mm incision. With this tip, he uses 100 percent torsional ultrasound with a vacuum setting of 350 mmHg, an aspiration flow rate of 35 mL/minute, and a bottle height of 100 cm. Additionally, the Intrepid Fluid Management System uses aspiration tubing that is much more rigid and less pliant than previous tubing. This provides extra surge protection and a more stable chamber. It also allows surgeons to perform safe and efficient phaco without the high flow rate that other systems require because of the higher bottle height. In fact, the Intrepid Fluid Management System allows a sufficient range of vacuum levels during micro-coaxial phaco with incisions as small as 2.2 mm and a bottle height less than 110 cm high.
The Monarch III IOL delivery system with the D cartridge allows surgeons to implant aspheric lenses through unenlarged 2.2-mm incisions. "It's all geared around making microincisional surgery safe and efficient so you don't have to put stress on the incision when you implant the IOL," Dr. Kim says. "The goal is to leave the eye with the same incision you started with. With bimanual phaco, for instance, some people are making a third incision to implant the IOL because the other incisions are not stable at the end of the procedure. With other microincisional systems, surgeons have to enlarge or stretch the incision." Compared to the C cartridge, the D cartridge has a nozzle with a 33 percent smaller tip and a 0.5-mm larger opening, resulting in minimal resistance upon IOL loading and atraumatic IOL implantation through the microincision.
The Alcon Intrepid Micro-Coaxial System allows surgeons to make a smooth and easy transition to microincisional cataract surgery with the advantages of better wound integrity, less wound leakage, and less surgically induced astigmatism, all of which should result in faster postoperative recovery and improved surgical outcomes, he adds.
Whitestar Signature System
Advanced Medical Optics has recently introduced Ellips Transversal Ultrasound. This provides benefits that are similar to torsional ultrasound, while allowing surgeons to use a straight tip. Ellips Transversal Ultrasound combines some longitudinal movement with a transverse elliptical path of the phaco tip.
"The transverse motion of the phaco tip allows more efficient consumption of lens material with less searching to find it and bring it to the tip, so it makes your emulsification and aspiration of chunks faster," says Mark Packer, MD, a clinical associate professor at Oregon Health and Sciences University, and in private practice at Drs. Fine, Hoffman, and Packer in Eugene, Ore. "It has improved followability so that if you have a chunk that you can bring near the tip, it will keep it moving on the tip so that it can be aspirated in an efficient way. This is true even for dense material."
David F. Chang, MD, agrees. "In terms of my own clinical practice, the most valuable feature on the Signature machine has been the addition of the Ellips," he says. "Like OZil, Ellips really reduces the repelling force that characterizes purely axial phaco tip motion." Dr. Chang is a clinical professor at the
Dr. Packer uses a chopping technique to divide the nucleus. He begins the case with conventional linear ultrasound for burying the phaco needle into the nucleus, holding it with high vacuum, and then chopping it to divide it up. "I will completely chop up the nucleus in that one setting," he says. "It's a long pulse with a 30-percent duty cycle. The reason I do that without the transversal or elliptical application is that it facilitates a good hold on the material. After chopping the nucleus, I switch to a second setting, which is transversal only, and bring each quadrant or piece up with aspiration. Then, I push the pedal down and just watch it disappear."
Dr. Packer uses an epi-nucleus setting, which is basically reduced power. If there is cortex left, he uses Venturi I/A, which is another advance on the Signature system. The system also has a Venturi capability for phaco, but it is not activated yet. "Using Venturi I/A is a good way for surgeons to get used to using Venturi and then maybe start using it for phaco as well," he says. "I was a little nervous about Venturi at first. I thought it was going to be so aggressive that I was going to be sucking in capsules left and right, but it turns out that it works really well." Using Venturi requires a different technique, however. Because there is vacuum at the tip, the surgeon needs to use gentler application of the foot pedal.
According to Dr. Chang, some longitudinal ultrasound is still desirable when surgeons encounter an extremely dense cataract. In that situation, he will use traditional longitudinal phaco to impale or partially sculpt the nucleus, if necessary. "I then try to use Ellips as much as possible with dense loose fragments in order to minimize chatter and bouncing particles at the tip," he says.
The Signature system also has other advantages over the Sovereign, which was AMO's prior flagship machine. "The new, modern user interface is a major improvement," says Dr. Chang. "The Signature also introduces a more efficient and responsive pump that provides the option of having either a peristaltic or a Venturi mode for I/A. A new wireless dual-linear foot pedal is about to be unveiled," he adds.
Stellaris Vision Enhancement System
The engineers who designed the Stellaris (Bausch & Lomb) began with a blank slate, says Terence M. Devine, MD. "They designed everything from scratch to work together, so it incorporates an entirely new pump system called a rotary vane system, which provides the ultimate vacuum system for a phaco machine. That is combined with state-of-the-art vacuum sensors so the system is monitoring vacuum at the pump and at the collection cassette. It feeds that information back to the computer," says Dr. Devine, who is chief of ophthalmology at the Guthrie Clinic in
One of the benefits of this combined technology is that, because the fluidics are so well-controlled and provide chamber stability, surgeons are able to use the machine to perform 1.8-mm phacoemulsification with a sleeve. "With bimanual, where you take the sleeve off and run the infusion through a separate incision, you can go smaller (1.5 mm or smaller). But with the sleeve on, with traditional coaxial phaco, we are able to go down to 1.8 mm, which is the smallest in the industry," he says.
Dr. Devine performs 1.8-mm coaxial microincision cataract surgery (C-MICS) on all cataract patients, enlarging the incision to implant the lens. "I think there is great advantage in the 1.8-mm C-MICS because the instruments are so much smaller and more maneuverable," he says. "If you are working with a [floppy iris] case with small pupils, having the smaller instrumentation gives you that much more room and that much more visibility."
When performing 1.8-mm C-MICS, Dr. Devine recommends ensuring that the fluidics settings are adjusted properly, and he recommends checking the bottle height. "Bottle height is important, and one thing to keep in mind is that all machines will give you a bottle height readout, but the machine doesn't know where the patient's eye is," he says, "so the true bottle height is from the fluid level in the drip chamber to the patient's eye. If you set the patient higher or lower than the reference point on the machine, the readout is going to be inaccurate."
Dr. Devine prefers using the smallest possible side-port incision. "I find that a 0.5-mm side port will allow any instrument to enter the eye, and the smaller incision reduces leakage, which makes the chamber more stable and safer during surgery," he adds.
While he prefers a small side-port incision, the other incisions should not be smaller than 1.8 mm because smaller incisions could crimp off the infusion sleeve, which would result in less fluid running into the eye and an unstable chamber.
"As you go smaller and smaller with phaco incisions, it is important to be a little more meticulous in sizing the incision," he adds. "I personally like to use a vacuum level of 300, but you can go up to 600 if you like, and there are some advantages to that. If you go above 300, I would recommend using StableChamber tubing. One thing that is unique about the Stellaris is the dual-linear foot pedal. It's a wireless Bluetooth foot pedal, and it not only controls the power in the up-and-down direction as all machines do, it allows you to control the vacuum levels by moving the pedal side to side so you have a dual linear function."
The Stellaris StableChamber tubing has a smaller diameter downstream, and the higher resistance reduces flow, according to Elizabeth Davis, MD, director of the Minnesota Eye Laser and
Dr. Davis also performs 1.8-mm C-MICS as her standard procedure. She notes that there is no learning curve to transition from standard coaxial phaco.
All three machines allow surgeons to perform safer and more efficient surgery. "The torsional ultrasound from Alcon is a real advance," Dr. Packer concludes. "The elliptical ultrasound that AMO subsequently introduced, which is kind of along the same lines, is equivalent to that. The machines have become a lot safer and more efficient with all of these incremental advances. It's a great time to be doing cataract surgery."
