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Up Front | Sep 2007

Why Bimanual is Better

In my opinion, bimanual microincisional cataract surgery has many benefits over coaxial.

At the beginning of this century—as ultrapulse technology was introduced—the diffusion of bimanual microincisional cataract surgery began. Lower temperatures in the phaco tip, guaranteed by this new technology, allowed surgeons to perform a sleeveless cataract extraction through two microtunnels. This technique presented many clear advantages in comparison with standard coaxial phacoemulsification, both in terms of safety and speed of visual acuity recovery. Since its conception and still today, and despite the fact that this technique is not as widespread as we may have expected it to become, I believe that bimanual microincisional cataract surgery is a viable option for cataract surgeons.

Less than 10% of European surgeons use a bimanual technique in the majority of their procedures. The reason behind this is not the learning curve, as most surgeons are very able in phaco and already use a bimanual I/A technique for cortical clean-up, but because of the absence of small-incision IOLs. Not many lenses are implantable through such a small incision, and the ones that are may not retain the optical performance available with most widespread IOLs on today's market.

Still, many surgeons want to transition to a smaller incision. With the introduction of smaller coaxial phaco incisions over the past few years (ie, 1.8-2 mm), we can no longer claim that microincisional cataract surgery is a synonym for bimanual microphacoemulsification.

Given the fact that both bimanual and coaxial are efficient techniques, we must pose a question: If it is possible to perform an operation with a coaxial handpiece through a microincision, does bimanual phaco still have reason to exist? Our answer is a definite yes, because the bimanual technique presents several advantages that qualify it as the best technique in most—if not all—patients today.

First, fluidics is better controlled with bimanual phacoemulsification. During coaxial, the phaco tip captures a portion of the irrigation flow immediately after leaving the sleeve. By having the irrigation flow near the aspiration, nuclear fragments may be pushed away. But, if you have irrigation on one hand and aspiration on the other, followability, holdability, and effective phaco time increase.

The second advantage is the statistically significant difference in the total volume of balanced salt solution used during the two techniques.1 In fact, there is a lack of fluid waste during bimanual phaco, because the surgeon may work without leakage from the tunnel. This creates a more stable environment and a reduction in endothelial damage.

Third, separate infusion and aspiration produces excellent surgical results in difficult cases or in instances where coaxial phaco would not be effective (eg, small pupils, floppy pupils that move during aspiration with a big risk in nicking the pupil margin). By directing the irrigation flow toward the iris during bimanual, the surgeon can hold the floppy pupil in place. Bimanual is also advantageous in patients with a limited zonular dialysis, because an open-ended chopper may be used. By holding the irrigation flow in the direction of the dialysis inside the bag, it is possible to maintain the bag's position and perform a safer procedure. In such a case, it is also possible to use a lower irrigation inflow. Because the irrigation may be directed away from the area of zonular dialysis, the risk of fluid misdirection syndrome is reduced.

Using an open-ended chopper allows one to take full advantage of the irrigating flow, which is one of the most important reasons why the open-ended irrigating chopper has come back into fashion and replaced lateral-opening choppers.

Bimanual has significant advantages over coaxial during standard procedures as well. First, when the phaco tip is held in the bag, it is possible to press down on the posterior capsule and work in safe conditions. It is also easy to direct the irrigation flow and remove nuclear fragments when they remain hidden in the anterior chamber angle, either under the iris or beneath the tunnel.

During coaxial phaco, however, one must remove the probe from the anterior chamber before removing the fragment under the tunnel. Otherwise, there is a risk of anterior chamber collapse when the phaco tip is pulled back to the incision site and the irrigation is blocked.

Concerning parameters that define the quality of a surgical technique, the question between bimanual and coaxial is continually debated. In my experience, no significant statistical difference arose when comparing the two techniques in terms of increased stromal thickness on postoperative day 1, corneal endothelium changes, (and best visual acuity), increased anterior chamber tension during surgery, or increased temperature at the incision site.

In my experience, bimanual microincisional cataract surgery presents several advantages in terms of safety and efficiency, when compared with the microcoaxial phaco. In fact, I think that once we have a lens capable of injection through a sub–1-mm incision, bimanual phacoemulsification will be the most widespread technique. Microcoaxial phaco may have reached its final stage of evolution, and it is difficult to think that it may be possible to perform coaxial through an incision smaller than the current size of 1.8 mm.

Oftentimes, we hear about surgeons who assume extreme positions. Some may say, "The bimanual technique presents so many advantages that it makes coaxial a thing of the past." Those who disagree may say, "Today, the bimanual technique has no reason to exist, because it is possible to perform coaxial phaco through a microtunnel." Although I think that neither position is correct, both techniques are worthy and innovative and should be part of every surgeon's working experience. Furthermore, we should keep in mind that both have specific indications, and each technique should be evaluated on an individual basis.

Alessandro Franchini, MD, is Professor of Ophthalmology at the School of Ophthalmological Specialization, University of Florence, in Italy. He states that he has no financial interest in the companies or products mentioned. Dr. Franchini may be reached at tel: +39 055 411765; fax: +39 055 4377749; or alessandrofranchini@yahoo.it.