Minimal stress technique offers advantages for cataract removal
This technique allows surgeons to perform extractions through a 1-mm incision.
--- Capsulorrhexis by cystotome under irrigation is performed without viscoelastics.
In the past years, the incision through which the cataract has been removed has grown progressively smaller. This has become possible because of new surgical techniques and constant technological advances.
With modern phacoemulsification, we are obtaining extractions through an incision of about 3 mm, a result that only a few years ago seemed impossible. The daily technological evolution allows the extraction of cataracts through an even smaller incision.
To further reduce the incision, some surgeons have tried to use a laser beam rather than ultrasound. We know today that laser emulsification requires more time to emulsify the lens and cannot be used on hard cataracts. The laser beam is transported by means of an optic fiber. The optic fiber must have a minimum diameter of 0.5 to 0.6 mm to transport a sufficient quantity of energy. Aspiration and fibers must be built into the same tube within the handpiece. This tube cannot have a wall less than 0.1 mm thick, which means that the aspiration lumen cannot be greater than 0.3 or 0.4 mm in diameter.
This is a very small space, possibly sufficient for the aspiration of soft cataracts, but not for the removal of harder fragments.
Within these conditions, the incision to pass the laser fiber rarely drops below 1.6 mm. Therefore, the laser emulsification allows aspiration of soft lenses through an incision that is slightly greater than 1.5 mm.
The laser technique presents other inconveniences, as well. The laser is an expensive instrument and the fibers cannot be easily autoclaved, but require a disposable sleeve that is not always accepted by international regulations on sterility, such as in France, where decontamination with highly alkaline liquids is mandatory by law for all reusable handpieces and cables.
Recently, though, I was offered the opportunity to try another method to remove the lens through a 1-mm incision.
Alternative removal method
The method uses traditional ultrasound, but a patented console unit that supplies energy to a specially designed four-crystal U.S. handpiece and to a Teflon-coated titanium tip.
The special Teflon-coated titanium tip was made with the cooperation of Philippe Crozafon, MD, and Optikon 2000 (Rome), which supplied the patented phacoemulsification unit, the Pulsar Minimal Stress. This Teflon-coated tip does not require a sleeve. The irrigation is fed through the service lateral incision widely used today in bimanual techniques.
The first time I used this new technique, I was afraid I would have corneal burns. But I came to realize that the combination of the low stroke made possible by the Pulsar Minimal Stress, the self-lubricating Teflon coating on the titanium tip, and the fluid out of the incision guarantees a sufficient cooling of the surrounding tissue. Furthermore, the small tip, without a sleeve, allowed me to move freely in the anterior chamber.
The cutting capability of this new device was surprisingly high, and I could sculpt the nucleus with an unexpected precision. The fluidics of the system are excellent, as all emulsified material was removed easily without any complications.
The U.S. driver works so well that the same day, I could attack more hard lenses and do more compelling cases with a sense of safety.
I was so enthusiastic that I decided to perform live surgery with the Pulsar during the international congress organized by Ocular Surgery News in Rome this year. Live surgery is an experience by itself, but it was a special event in this case, as I developed a deep discussion with my colleagues that continued for many days with many of my surgeon friends.
In my opinion, this new technique presents necessary surgical variations compared with traditional phacoemulsification, creating doubts that had to be resolved.
Minimal stress technique
I begin by making two 1 mm corneal incisions, very near to the limbus, at the 10:30 and 1:30 positions.
The first problem to solve is how to make the capsulorrhexis. Because of the size of the incision, we cannot use traditional forceps. I suggest the use of either a cystotome or one of those forceps used by retinal surgeons.
The second problem is the use of viscoelastic materials. By using viscoelastics, we create a perfect anterior chamber, which is extremely useful during rhexis, but creates problems during hydrodissection. The viscoelastic material does not leave the anterior chamber easily using irrigation. I had to use forced aspiration to remove it during this phase.
Personally, I found it easier not using viscoelastics in this phase, therefore proceeding as follows:
I insert a cannula in the left incision, leaving a constant flow of irrigation to maintain the deeply formed anterior chamber.
I insert a modified vitreous forceps in the right incision and I perform capsulorrhexis under irrigation. The overall maneuver is simpler than it seems. The capsular edge tends to flutter, but it remains well separated from the cortex. By moving the irrigation cannula, we can keep the capsular edge under control. Hydrodissection is easy and will always be performed under irrigation.
At this point, I insert the Teflon-coated 0.7-mm titanium tip. The titanium tip is thin and is long enough to be handy. The minimal stress technique and the Teflon-coated tip give the surgeon the impression that he or she could almost write his or her name on the nucleus!
I maintained a stroke of no more than 30 to 40 µm at all times. (The Pulsar Minimal Stress is the only unit that measures the tip stroke and gives a precise reading of it, instead of a percentage of an unknown U.S. power value.)
The sculpting is very precise, with minimum stress on the zonules.
With this new technique, I suggest that a higher vacuum level and flow be maintained to increase safety.
The irrigation cannula, inserted through the side incision, can be used as a manipulator, and in this case as well, the irrigation flow may be directed to mobilize the fragments.
Sometimes with traditional phaco units, the irrigation fed by the coaxial sleeve tends to push the material to be emulsified away from the titanium tip. With the bimanual technique and the Pulsar Minimal Stress, the followability is certainly much higher. The high maneuverability of the new tip and the lateral irrigation make the epinucleus emulsification much easier.
To remove the cortex, we use the classical irrigation and aspiration tips. At the end of the case, we regrettably had to enlarge the incision to insert the IOL. However, the entire case was treated safely by all points of view — the anterior chamber was deep and closed, the energy used was maintained at the very minimum to prevent endothelial damage and corneal burns, a small coated tip with high maneuverability was used, as well as a minimum use of viscoelastic material.
At this point, what is missing is a lens that can be introduced through a 1-mm incision. Technology is finally available to give us the possibility of making an affordable 1-mm extraction. We surgeons are ready.
For Your Information:
- Giuseppe Panzardi, MD, is assistant professor of ophthalmology at the University of Florence, Italy. He can be reached at Via Piagentina 25, 50121 Florence, Italy; e-mail: email@example.com. Dr. Panzardi has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- For more information on the Pulsar Minimal Stress phacoemulsification unit, contact Optikon 2000, Via del Casale di Settebagni, 13, 00138 Rome, Italy: (39) 06-88-88-355; fax: (39) 06-88-88-388; e-mail: firstname.lastname@example.org.