Bimanual phaco in an eye with traumatic zonular dialysis.
Bimanual phaco chop is performed using high vacuum.
(All images courtesy of David F. Chang, MD.)
Ocular Surgery News, January 15,2004
Surgeons skeptical
of bimanual phaco
Technology
has not kept pace with enthusiasm, some surgeons say.
Beth Herskovits
Attention, press and controversy have surrounded the growing interest in the concept of bimanual microincision phacoemulsification. The technique has been billed as part of the movement toward increasingly less invasive surgery.
But some surgeons say that the technique is not yet ready for widespread use in the United States and that the introduction of suitable machines and instrumentation – especially a suitable IOL – must precede its adoption by the ophthalmic community.
The bimanual technique is still in the early development phase and only “early adopters and innovators” have really begun to perform it, according to Richard L. Lindstrom, MD.
Dr. Lindstrom, chief medical editor of Ocular Surgery News, recalled polling participants of the Ocular Surgery News Symposium on Cataract, Glaucoma and Refractive Surgery in New York. He said that none of the 250 audience members and only four of the eight panelists had even attempted bimanual phaco.
“For the general ophthalmologist … there’s no reason to make that transition at this time,” Dr. Lindstrom said. “I think most surgeons are wise to go slowly.”
Several manufacturers are upgrading their phaco systems to prepare for widespread use of the bimanual technique. Yet this move is largely strategic, designed to keep ahead in a full and competitive market, according to Dr. Lindstrom.
Moreover, it is the consultants of these companies who are mainly using the bimanual technique at this time, he noted.
David F. Chang, MD, is one such surgeon who first became interested in the technique while working with the WhiteStar technology that is incorporated in Advanced Medical Optics’ phacoemulsifier.
“Certainly, everyone is interested in the potential for smaller incisions,” he said of bimanual phaco. “The problem is that with current IOL technology, I end up with the same incision size and anatomic result regardless of whether I do bimanual or coaxial phaco. Therefore, the question becomes whether this technique is better at removing the nucleus. As long as the incision size is the same, surgeons will only transition to bimanual if it improves safety or efficiency.”
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(All images courtesy of David F. Chang, MD.) |
The promise of bimanual phaco is the ability to perform cataract surgery through a microincision of less than 2 mm.
Two microincision IOLs are currently available in Europe from ThinOptx and Acri.Tec. Neither company’s IOL is approved in the United States. Therefore, Dr. Lindstrom noted, “I’m primarily speaking to the U.S. surgeon when I say it’s premature.”
Dr. Chang said that he performs the bimanual technique in less than 10% of his patients. “I have been quite interested in evaluating and improving this technique,” he said. “This is the only way we’ll learn whether and where it is useful. I am impressed that our instrumentation has improved significantly in the past year.”
Dr. Chang said that he would perform the procedure in a larger number of patients if microincision IOLs become available in the United States. But whether a reduced incision size will provide major advantages over current incisions is also a “big if,” he said.
Some surgeons argue, however, that the bimanual technique is limited by more than the lack of a suitable IOL. According to Richard J. Mackool, MD, the bimanual technique prevents the use of high flow and vacuum technology during the cataract procedure.
High flow and vacuum rates offer an alternative to using ultrasonic energy or can result in dramatic reduction of the energy required to remove the nucleus, according to Dr. Mackool. These energy sources produce less dispersal of nuclear fragments within the eye and decrease the risk of endothelial damage, he said.
“In my opinion, any retreat toward using lower flow and lower vacuum levels to remove the nucleus is a step in the wrong direction,” he said. “I believe the laws of physics are squarely against the bimanual technique.”
Dr. Mackool also noted that the bimanual technique is compromised by the inability to use an infusion sleeve during the procedure, therefore significantly limiting the amount of infusion that can be delivered.
He also criticized the technique because it requires incisions that are not watertight. The incision must leak in order to prevent thermal injury, he noted.
“The so-called bimanual technique requires the incision to leak significantly because that’s how the tip remains cool. It’s not ‘cool phaco’ – the phaco needle still creates thermal energy, but you’re taking it away by having fluid run alongside it. That’s the easiest way to cool anything,” he said.
Dr. Mackool noted that even with these disadvantages, “There is simply no evidence or reason to presume that two 1.4-mm incisions are better than one 2.8-mm incision.”
Dr. Chang agreed that, initially, low infusion rates made the procedure “less forgiving” and necessitated working at lower vacuum settings. But he noted that new advances – such as better irrigating choppers and STAAR Surgical’s Cruise Control device – may now enable surgeons to overcome the earlier fluidic limitations of bimanual phaco.
“The Cruise Control flow restrictor allows me to work at the same high vacuum settings that I use with coaxial phaco,” he said. “This makes bimanual a viable alternative to coaxial phaco, but at this point, I don’t think it is superior.”
Dr. Chang also said that bimanual low-flow phaco techniques are advantageous in certain circumstances.
“In traumatic cataracts with large zonular defects, bimanual phaco allows me to dissociate the irrigation and aspiration ports,” he said. “Along with a reduced infusion rate, this reduces the chance of fluid misdirection. For similar reasons, bimanual instrumentation might also be advantageous if one were continuing to phaco in the presence of a posterior capsular defect.”
He added that he also prefers bimanual I&A to coaxial I&A whenever there are capsular complications.
Dr. Lindstrom also noted that bimanual I&A could prepare surgeons for performing bimanual phaco. Furthermore, “there’s an advantage to bimanual I&A that’s real and measurable,” he said, in that the technique allows easier removal of subincisional cortex.
He added that once instrumentation is available that would allow equivalent safety and control for bimanual phaco, surgeons may be able to see small benefits with that technique as well. For instance, he noted, the two microincisions, placed 90º apart, would be “astigmatically neutral.”
Yet both Dr. Chang and Dr. Lindstrom acknowledged that the bimanual technique is more awkward and difficult to control than a coaxial technique and carries a significant learning curve.
“At this time, most surgeons will not find any major advantage to bimanual phaco, so there’s not much of an impetus to change from something with which they are already quite familiar and comfortable,” Dr. Chang said. “Bimanual I&A is a good analogy. It works well, it is advantageous with capsule complications, and some surgeons prefer to use it routinely. However, the majority of us still choose coaxial I&A for routine cases because it is a bit faster and more efficient.”
Dr. Lindstrom said that until the necessary instrumentation is developed, surgeons will be forced to enlarge one of the two bimanual incisions to insert an IOL, and they can expect the total size of the incisions to be equal to or greater than the single incision required in coaxial phaco. “The major potential benefit is not really achieved,” he said.
