Phacoemulsification was first described in the literature by Charles Kelman in 1967.¹ His report described cataract removal with ultrasonic energy to disrupt the hard nucleus and aspirate the cataract. Despite its slow ascension into surgical practice, the evolution of phacoemulsification continues as surgeons strive to improve patient outcomes.

One such technique — bimanual microincision phacoemulsification — is gaining worldwide attention. This attention, however, is not without controversy. Advocates of bimanual microincision phacoemulsification argue that the technique is the safest, most effective and least invasive approach available. Challengers are weary of the transition to bimanual microincision phacoemulsification because of the associated learning curve and their current positive results with coaxial phacoemulsification.

INCISION SIZE
There is little difference between bimanual microincision phacoemulsification and microincision coaxial phacoemulsification. Perhaps the most noticeable difference is the size of the incision; bimanual incisions are smaller. The other major difference is the use of unsleeved instruments during bimanual phacoemulsification surgeries that include separating the phaco from the irrigation.

"This is a natural evolution of cataract surgery, said Jorge L. Alió, MD, PhD, professor and chairman of ophthalmology, Miguel Hernandez University, and medical director of VISSUM Corp, Spain. Dr. Alió uses bimanual microincision phacoemulsification (or microincision cataract surgery [MICS], as he prefers to call it) in 90% of his cases. He has been using this technique for 2 years and previously used coaxial for 10 years. "In the last 20 years, we have made a tremendous change toward a smaller incision, and the size of the incision and the development of technology are parallel, he said in an interview with Cataract & Refractive Surgery Today Europe.

USED BY HIGH-VOLUME SURGEONS
Dr. Alió estimated that 15% of European surgeons are using bimanual microincision phacoemulsification, the majority of which are high-volume surgeons. Another 20%, he said, are curious about and have experimented with the technique. "The surgeons who use it by definition have larger practices and most likely they are high-volume [surgeons] because they provide a better outcome for their patients.

One surgeon who has experimented with bimanual microincision phacoemulsification is Brian Little, MA, DO, FRCS, FRCOphth. After experimenting, Mr. Little, of the Royal Free Hospital, London, decided to return to his personalized horizontal chopping technique. He uses a limbal incision with the Millenium Microsurgical System (Bausch & Lomb, Rochester, NY), Custom Controlled Software (Bausch & Lomb) and micropulsing.

"I chose this technique for the same reasons that all surgeons select their preferred technique: Because in my hands and with my current level of experience using the instrumentation available to me, I have found that it is the safest and most efficient means of removing the majority of cataract types, he said. He has performed more than 2,000 cases in 4 years. "Ultimately, the question that we all have to address is, 'Why should we shift outside our surgical comfort zone if we are already using a safe and successful technique?' Any phaco technique takes years to refine, and if it gives us predictable and perfectly good results, then why change it?

Mr. Little said he would transition to bimanual microincision phacoemulsification only if enough clinical evidence demonstrated a significant benefit over other phaco techniques in the areas of surgical safety or visual outcome. Although he sees no major disadvantages or unique complications associated with bimanual phacoemulsifiction, ascending the learning curve is associated with finite risks that may not outweigh the benefits. "At this time, I am not convinced that there is a compelling case to change [to bimanual microincision phacoemulsification], bearing in mind what that change may involve, he said.

Advocates of bimanual microincision phaco, however, argue that the technique's advantages prevail over the risks. I. Howard Fine, MD, made a full transition from coaxial phacoemulsification more than 3 years ago. The learning curve, he said, was short and with minor risks. Dr. Fine practices privately at Drs. Fine, Hoffman & Packer, Eugene, Oregon. He is clinical professor of ophthalmology at the Casey Eye Institute, Oregon Health & Science University. He said that refractive lens exchange patients, especially, have benefitted with bimanual microincision phacoemulsification (Figure 1).

"Once we have lenses that go through a 1.1-mm incision, bimanual microincision phaco will become the standard of care, he said. "I think that probably within 5 years, we will see a major shift in that direction. This shift will occur when more IOLs designed to enter through smaller incisions are available, he told Cataract & Refractive Surgery Today Europe.

Pros
Fluidics
Although many surgeons assume incision size is the greatest benefit of bimanual microincision phaco, Dr. Fine said it is actually improved fluidics through the separation of aspiration from irrigation. Exceptional fluidics control is achieved by supplying irrigation and aspiration, Dr. Alió said, adding that this technique offers less recovery time for patients, lower surgical costs and produces a higher quality surgery.

In bimanual microincision phacoemulsification, the fluid enters the eye on one side and leaves through another. Therefore, no competing fluid currents surround the phaco tip, and volume is created in the capsular bag. In the presence of a sleeved phaco tip, "there is aggressive outpouring of fluid surrounding it, Dr. Fine said. Additionally, in bimanual microincision phacoemulsification, fluid is circulating in the anterior chamber and it is possible to mobilize and phaco nuclear material in a broken capsular bag (Figure 2). This cannot be done with coaxial phacoemulsification because fluid surrounding the phaco tip will push the nuclear material into the vitreous, Dr. Fine said.

"Early adopters who experienced the bimanual epiphany tend to eulogize about the superior fluidics and chamber stability that not only sound appealing but also look wonderful on video, Mr. Little said. "With the right instruments, correctly-sized incisions, good control of the fluidics and an appropriately developed skill set, this is all clearly possible. However, my early cases were not anywhere near as aesthetically attractive, and I have found this stage of surgical nirvana more difficult to achieve in practice than I anticipated.

With further advancement of phaco machinery, more control of fluidics is possible, Dr. Alió said. "We will have the opportunity to further improve our surgical capabilities and surgical skills by using this technique.

Incision size
Incision size is an advantage because it is safer and causes less astigmatism. Alió et al² showed that a byproduct of microincision surgery is astigmatism. With the bimanual technique, Dr. Alió said it is possible to control astigmatism induced by the procedure.

"An ideal system would be one that is completely closed: no incision and no leakage, Dr. Fine said. "We get less incision leakage with bimanual microincision phacoemulsification. Smaller incision sizes also create a more stable chamber. This, Dr. Alió commented, is the second major advantage to bimanual phacoemulsification.

Difficult cases
Bimanual microincision phacoemulsification may provide distinct advantages during difficult and complicated cases, Dr. Fine said. For instance, the risk of retinal detachment may be reduced during cataract surgery in highly myopic eyes. This is due to a stabilization of the vitreous face by keeping the irrigator in the eye throughout the case to maintain the chamber. This is also beneficial in eyes with posterior polar cataracts (Figure 3), Dr. Fine said. In this instance, the irrigator will help stabilize a potentially open posterior capsule by not allowing trampolining of the lens. "With the use of viscoelastics, you can avoid spilling lens material into the vitreous or bringing the vitreous forward, he said.

Placing the phaco needle in the opposite hand during bimanual microincision surgery in eyes with zonular dialysis may cause closing of the dialysis. This, Dr. Fine said, cannot be done with coaxial phacoemulsification.

Bimanual microincision phacoemulsification forces the use of micropulsing power modulation, which is an added benefit of this technique.³ "But, the benefits of this technology can still be reaped using a coaxial handpiece, Mr. Little said.

Micropulses, Dr. Alió said, improve phacoemulsification, and decrease ultrasound use and surgical aggressiveness. The power is used in a limited extent and is followed by periods absent of ultrasound. "During these periods, high vacuum may have a strong effect aspirating the cataract remains and even the cataract itself, depending on the hardness, he said. "By doing this, we better use ultrasound and this reduces the phaco time.

CONS
Learning curve
Most surgeons agree that perhaps the largest drawback associated with the bimanual microincision phaco transition is the learning curve. Along with learning a new technique, surgeons will face anxiety, encounter new complications and possibly disrupt their satisfactory patient outcomes.

"These are reasonable fears, Dr. Fine said. "But, that has been true of every advance. It was true of phaco when it first came out, it was true of extracapsular surgery when it came out, and it was true of refractive surgery. Any advance that challenges the status quo gets the establishment nervous, and surgeons may search for reasons to not use the new development.

"The adoption of any new technique, no matter how potentially beneficial, inevitably involves some additional risk, said Mr. Little. "To feel that such a risk is justified, a surgeon has to be convinced that there is a worthwhile and tangible benefit in either surgical safety or improved outcomes that outweigh the risk of the transition.

Many surgeons feel safer using their current technique because of the positive results it produces. "But, it is not a way to progress your practice, Dr. Alió said. "Effective surgeons, the ones who accept challenges and are looking for something better for the future of their practice, for their patients and for the evolution of ophthalmology, they will be or already are involved in bimanual microincision cataract surgery.

Instrumentation
Learning how to use new tools (Figure 4) may also provide a disadvantage to those surgeons performing the technique for the first time. Such tools include irrigating choppers, microcoaxial rhexis forceps and knives that match the diameter of the phaco. Furthermore, Dr. Alió said that an improvement is needed in the current instrumentation. Surgeons including Iqbal Ike Ahmed, MD, FRCSC (University of Toronto, Canada), Richard S. Hoffman, MD, and Marc Packer, MD, (Casey Eye Institute, department of ophthalmology, Oregon Health and Science University, and in private practice at Drs. Fine, Hoffman & Packer, LLC), along with Drs. Alió and Fine, are developing new instruments for bimanual microincision phacoemulsification.

Another drawback is the vast number of available instruments, Dr. Alió said, because not all of them are good. One instrument with several available models is the irrigating chopper. Many choppers currently on the market do no provide proper fluidic volume. "This leads to microlapses during surgery, Dr. Alió said.

According to some, upgrading machinery to bimanual microincision phacoemulsification standards may be costly. "There is a small difference in equipment, Dr. Fine said.

Dr. Alió said that bimanual microincision phacoemulsification may be performed with most phacoemulsification machines. "The main issues are to realize that high vacuum has to be compensated in the fluidic inflow and that adequate instruments should be used with adequate incisions to avoid leakage, he said.

IOLs
vailability of IOLs is also another concern; only a few designs including the Thinoptx Ultra Choic 1.0 IOL (Thinoptx, Abingdon, Virginia), the Acriflex MICS 46CSE (Acrimed GmbH, Berlin, Germany), Careflex (W20 Medizintechnik AG, Bruchal, Germany), Superflex and C-flex IOLs (Rayacryl Rayner LTD, UK), IOLtech microincision lens (IOLtech SA, Zeiss Meditec A, Jena, Germany), the Tetraflex KH-3500 (Lenstec Inc, Florida) and the Acrismart (Acri.Tec GmbH, Hennigsdorf, Germany) can pass through a microincision. "If you don't have [access to] the available lenses, you may question the decision to make an evolution toward a new technique in which you still have to enlarge the incision later for the IOL, Dr. Alió said. In fact, there will be no protection from astigmatism if the technique is performed without the correct IOL, he said. "But, in my opinion, you should be trained in bimanual microincision surgery because you will learn a surgical technique that is better for the eye.

Seals, Leaking and Using One Hand
Bimanual microincision phacoemulsification may not create an adequate seal, Mr. Little said. "Unless the incisions are perfectly dimensioned and exactly matched to the instruments, they may not seal as well because any round cannula will open a linear wound into an ellipse.

With the horizontal chopping technique, Mr. Little is also able to stabilize the chamber and eliminate side-port leakage by extracting the second instrument in the final removal of the lens fragment. The advantage provided by this move is that the fragment may be removed with one hand. This is not possible with bimanual microincision phacoemulsification, he said. It also allows for an effective seal because the soft silicone irrigation sleeve passively adapts to the profile of the wound. In bimanual microincision phacoemulsification, the irrigation tool is the second instrument, which, therefore cannot be removed.

FUTURE OF CATARACT SURGERY
Regardless of the technique, phacoemulsification continues to undergo improvements. The future of cataract surgery will depend on the technology available and the willingness of surgeons to transition to newer techniques that may be safer and more effective. Despite the controversy surrounding bimanual microincision phacoemulsification, its use will continue to grow in Europe and worldwide.

Surgeons like Dr. Alió who have already transitioned to bimanual microincision phacoemulsification testify that the technique is superior because it better controls astigmatism and better uses fluidics. Others who are not yet convinced that it is an advanced technique are keeping a careful eye on current research.

"The future widespread adoption of bimanual microincision phacoemulsification may occur if there is a sufficient body of convincing evidence that demonstrates its tangible benefits over smaller-incision coaxial phaco, Mr. Little said. "At the moment, bimanual microincision phacoemulsification is in its early stages, and there is probably insufficient incentive for most surgeons to change from their safe and successful coaxial technique.

"Phacoemulsification is a superb development, and we should celebrate its continued refinement as well as its diversity, Mr. Little continued. "It is not a question of 'either/or,' but a question of personal decision as to whether or not the time is right to try a new technique once any significant advantages to the patient are unambiguously clear.

Jorge L. Alió, MD, PhD, is professor and chairman of ophthalmology, Miguel Hernandez University, Alicante, Spain and medical director of VISSUM Corp, Spain. Dr. Alió may be reached at jlalio@vissum.com or +34 96 515 00 25. Brian Little, MA, DO, FRCS, FRCOphth is clinical head of cataract service at the Royal Free Hospital, London. He may be reached at brianlittle@blueyonder.co.uk.

I. Howard Fine, MD, is clinical professor of ophthalmology at the Casey Eye Institute, Oregon Health & Science University, and he is in private practice at Drs. Fine, Hoffman, & Packer LLC, Eugene, Oregon. Dr. Fine is a paid consultant for Advanced Medical Optics, Bausch & Lomb, iScience and Carl Zeiss Meditec. He receives research and travel support from Alcon Laboratories Inc, STAAR Surgical, eyeonics Inc. and Rayner, but he has no financial interest in the products or other companies mentioned. Dr. Fine may be reached at hfine@finemd.com or +1 541 687 2110.

1. Kelman CD. Phaco-emulsification and aspiration: a new technique of cataract removal. A preliminary report. Am J Ophthalmol. 1967;64(1):23-35.
2. Alio J, Rodriguez-Prats JL, Galal A, et al. Outcomes of microincision cataract surgery versus coaxial phacoemulsification. Ophthalmology. 2005;112:1997-2003.
3. Fine IH, Hoffman RS, Packer M. Use of power modulations in phacoemulsification: Choo-choo chop and flip phacoemulsification. Journal Cataract Refract Surg. 2001;27:188-197.