Settings for Transversal Phaco

Phacoemulsification has become the preferred method for cataract removal since Charles D. Kelman, MD, introduced it in 1967. Kelman phacoemulsification, also known as longitudinal phacoemulsification, works by several mechanisms, the most important of which is the jackhammering effect. This effect is obtained via ultrasound-driven oscillation of the phaco tip. Each oscillation results in sinusoidal displacement transmitted to the phaco tip. During each forward displacement, one jackhammer impact is delivered to the lens to emulsify it inside the anterior chamber.

Although the jackhammering effect of longitudinal phaco is effective for cataract removal, it sometimes works against the surgeon. While it causes lens destruction during forward tip movement, it does nothing but generate heat during retraction. This heat, a result of friction, may jeopardize the cornea at the site of the main incision. At the same time, during forward movement, the phaco tip tends to repel nucleus material. This reduces ultrasound efficiency by requiring unnecessary excess use of ultrasound power. The final result is damage to the intraocular structures, mainly the corneal endothelium.

Currently, ophthalmologists are weighing the benefits of several newer ultrasound technologies, including torsional and transversal phaco machines, against their traditional longitudinal devices. The main objective for these technologies is to reduce the total ultrasound energy delivered inside the eye, and, at the same time, improve efficiency.

In contrast to longitudinal phaco, torsional phaco cuts lens material by shearing stress through circular oscillations of the phaco tip. When the tip swings from side to side, it does not repel the lens material but rather maintains longer contact with it. This makes torsional phaco faster and more efficient than longitudinal phaco, as it requires less phaco energy.

Some surgeons have experienced phaco tip clogging with torsional technology, especially in hard cataracts. Clogging interrupts surgery, as the surgeon is required to remove the tip from the eye to get it cleared before starting again. This issue compelled surgeons to work with new phaco tip designs with different tip bevels, and, most important, to add some of the longitudinal movement of traditional phaco to the torsional element. The resulting technology is dubbed transversal phaco. This article highlights a few tips to help surgeons achieve the maximum potential of transversal phaco.

ELLIPS TRANSVERSAL PHACO

In 2007, Abbott Medical Optics Inc. introduced the Ellips transversal ultrasound handpiece for its WhiteStar Signature system. Unlike torsional phaco, transversal phaco involves oscillation of the tip from side to side in a horizontal (transversal) manner. Another main difference is that transversal phaco incorporates longitudinal movement with the transversal component. As a result, the phaco tip moves in an ellipse-shaped manner (Figure 1).

The transversal phaco modality can be used with either a straight or bent phaco tip. The working frequency is 28 kHz, and the transversal-to-longitudinal movement ratio is 3:1. We obtain the best of both worlds by combining longitudinal and transversal movements. Nuclear fragments are exposed to shearing stress and the jackhammering effect caused by transversal and longitudinal motion, respectively, yet without the repulsion seen in longitudinal phaco. In transversal mode, cavitation is generated in the region around the tip, including the sides, rather than just at the front as with longitudinal phaco. An additional advantage is that transversal phaco can be obtained in continuous or hyperpulse (WhiteStar) ultrasound form for added safety.

The transversal technology was further improved with the introduction of the Ellips FX system in 2009. The Ellips FX technology features three main modifications compared with the preceding version: (1) the working frequency is increased by 45% to 38 kHz; (2) the stroke length of the transversal tip movement is intensified by threefold; and (3) the transversal-to-longitudinal ratio is modified to 1:1.

In a laboratory study, thermal rise and cutting efficiency with the Ellips FX (50% amplitude with WhiteStar) was compared with torsional ultrasound (100% amplitude).¹ Thermal rise at 1 second was 3.5°C with Ellips and 9.9°C with torsional ultrasound. The cutting rate into lens material was 1.7 mm/sec with Ellips and 0.6 mm/sec with torsional ultrasound.

FROM LONGITUDINAL TO TRANSVERSAL

Among the advantages of Ellips transversal phaco are that the surgeon does not have to modify his or her preferred technique or embrace new tip designs. I found the transition from longitudinal phaco to transversal phaco using Ellips technology to be smooth, with no learning curve. I could employ my standard quick-chop technique, as with longitudinal phaco. All I had to do was activate the Ellips software through the machine control panel. My preference for power setting is Ellips combined with WhiteStar hyperpulse ultrasound together with variable duty cycle.

My first impression was that this technology improved intraoperative followability of the nuclear fragments with less wound stress and edema. There was also a decreased incidence of corneal edema on the first postoperative day.

I did not encounter tip clogging in any cases of hard cataract; this can be attributed to the longitudinal component that is active at all times in conjunction with the transversal movement. I surmise that the role of longitudinal phaco on such occasions is to lessen the workload on transversal phaco. This is most likely achieved by its inherent jackhammering effect and by pushing lens material away to place it at the ideal plane for shearing in front of the phaco tip. Even though my power setting was 100% at times in some cases with brunescent nuclei, most patients could enjoy clear corneas on the first postoperative day.

SETTINGS WITH ELLIPS FX

I found that the modifications included in Ellips FX enormously expanded the cutting efficiency of the transversal ultrasound without losing its merits of improved followability. The resulting superfluous power enabled me to decrease the power setting from 100% ultrasound with the earlier Ellips to 50% with Ellips FX, and more recently, to only 35% in brunescent cataracts. Yet, I have encountered no tip clogging thus far.

Because of the enhanced ultrasound efficiency without repulsion, higher fluidics parameters have become unnecessary, and they could be managed down in consort with the power setting. My current setting for flow rate is within 24 to 32 cc/min. I often set maximum vacuum between 320 and 350 mm Hg. The Chamber Stabilization Environment (CASE) vacuum, with which emulsification occurs before occlusion break, is set to only 200 mm Hg in most cases (Figures 2 through 4). Less ultrasound leads to lower flow rate and vacuum settings, which, in turn, result in less irrigation fluid and thus less turbulence inside the anterior chamber. The final outcome is clearer corneas and faster visual recovery.

THROUGH A 2.2-MM INCISION

In conjunction with improved phaco and IOL technology, the modern cataract surgery paradigm has been shifted toward smaller wound size. Phacoemulsification and IOL implantation can now be safely performed through a 2.2- mm incision. My experience using the Ellips FX technology through 2.2-mm incisions has been positive.

The 20-gauge phaco tip with the Signature phaco platform can be used safely, although it was not designed for microcoaxial cataract surgery. The tip has an outer diameter of 0.9 mm and is available in straight and curved forms. I prefer the curved tip, as I believe it is easier to introduce through a 2.2-mm incision and provides better contact with lens material inside the anterior chamber. Some compression of the sleeve is expected at the main incision, and this may reduce the amount of irrigating fluid entering the anterior chamber. Despite this, I have not encountered anterior chamber turbulence during phacoemulsification (likely because of my relatively low fluidic settings). These settings would be impractical with longitudinal ultrasound in high-vacuum phaco techniques.

We conducted a study to evaluate clinical outcomes with Ellips FX using the Signature platform for cataracts between N2+ and N4+ on the Lens Opacities Classification System III scale. All surgeries were performed through 2.2-mm incisions using a 20-gauge curved tip. For a video demonstration, visit eyetube.net/?v=julog.

We noticed improved followability with a reduction in the average percentage of ultrasound power compared with former Ellips transversal phaco. Prior to IOL implantation, we measured the amount of wound stretch caused by the phaco tip-sleeve combination. The amount of wound size increase ranged from 0 to 0.2 mm (Figure 5). This suggests that transversal movements of the phaco tip did not exhaust the cornea at the main incision site. Four weeks after surgery, mean postoperative endothelial cell loss was 40.03 ±37.54 cells/mm2, which represents a 1.7% loss compared with preoperative values. Mean postoperative central corneal thickness increase from preoperative was 28.1 ±23.6 μm. We concluded that, because of the enhanced power modality of Ellips FX transversal phaco, off-label use of the 20-gauge tip through a 2.2-mm incision was effective and safe for N2+ to N4+ cataracts.²

Recently, 21-gauge phaco tips have been released with a light-blue sleeve for 2.2-mm and 2.4-mm incisions. These tips are available in straight and flared forms, with 30° and 15° bevel.CONCLUSION

Transversal phaco embraces continuous longitudinal phaco, which prevents tip clogging and places nuclear fragments in front of the phaco tip for better shearing. Switching from longitudinal to transversal phaco requires no change in technique or phaco tip. The transversal Ellips FX enhances power efficiency, enabling the surgeon to decrease power and fluidics settings without affecting the fluency of phacoemulsification. Lower power and fluidics parameters mean better outcomes and faster visual recovery. Additionally, 21-gauge tips for microcoaxial phaco with Ellips have been released, although we have found off-label use of 20-gauge tip to be safe and effective.

The author acknowledges Ahmed Osama Hashem, resident in ophthalmology, at Ain Shams University, for collecting references and data required for this article.

Ahmed Assaf, MD, FRCS(Ed), is an Assistant Professor of Ophthalmology, Ain Shams University, Cairo, Egypt. Dr. Assaf states that he has no financial interests in the products or companies mentioned. He may be reached at tel: +2 (02) 22705761; e-mail: assaf.ahmed@gmail.com.

1. Schafer ME.Laboratory evaluation of a next generation transversal ultrasound system.Paper presented at:the American Society of Cataract and Refractive Surgery Annual Meeting;April 9-14,2010;Boston.
2. Assaf A.Intraoperative and clinical results of newer transversal and torsional phacoemulsification through 2.2 mm incision. Paper presented at:the European Society of Cataract & Refractive Surgeons Annual Meeting;September 19,2011;Vienna,Austria.