Challenging and complicated cases including zonular weakness or partial dehiscence, posterior capsular rupture, floppy iris syndrome, and corneal endothelial dystrophy share one common problem: Higher intracameral fluid streams negatively affect the outcome of these procedures. In this article, I will outline the benefits of using torsional ultrasound phacoemulsification during these challenging cases.

HIGH FLOW, HIGH VACUUM DISADVANTAGEOUS
A high aspiration flow in the anterior chamber will inadvertently attract vitreous or a floppy iris toward the phaco tip, which may lead to further complications and potential visual loss. In endothelial dystrophy cases, high flow and turbulence in the anterior chamber will evacuate viscoelastic substances, which protect the fragile corneal endothelium from further damage by ultrasound energy. The direct impact of bouncing nuclear fragments and excessive fluid turbulence in itself may also cause endothelial cell loss with subsequent corneal decompensation.

A high vacuum setting will cause significant surge flow on occlusion break, and anterior chamber instability will result. Such a sudden chamber pressure change may destabilize a complicated situation, and in the case of a capsular rupture, nuclear pieces drop into the vitreous. If zonular dehiscence is presented, additional zonules tear from their base due to the change in chamber pressure.

To overcome repulsion with longitudinal ultrasound, high settings are necessary. Low settings are cumbersome with longitudinal ultrasound. Nevertheless, a nucleus of a certain density requires a certain vacuum and flow setting. With the right setting, the repulsive effects of the forward strokes of the longitudinal ultrasonic tip movements are defeated. Lower fluidics settings will result in a lower holding power of the nuclear pieces. This may cause chatter and nuclear fragments scattered in the anterior chamber, which result in prolonged manipulation in the eye and an increased risk for complications.

LOW FLUIDICS SETTINGS MANDATORY
Low fluid dynamics settings are mandatory for a successful outcome in these challenging cases. A low aspiration flow of 20 mL/min or less and a low bottle height help to prevent the vitreous or iris getting caught by the phaco tip. A low vacuum setting of 250 mm Hg will cause less surge flow on occlusion break and less pressure variance during the procedure. But, as previously mentioned, these low parameters will not provide enough holding power during quadrant removal with traditional longitudinal ultrasound.

TORSIONAL ULTRASOUND
Recently, torsional ultrasound phacoemulsification with the OZil handpiece (Alcon Laboratories, Inc., Fort Worth, Texas) was introduced as a new energy delivery modality on the Infiniti Vision System (Alcon Laboratories, Inc.). The oscillatory motion at the hub and shaft of the phaco tip is similar to NeoSoniX (Alcon Laboratories, Inc.), but the amplitude has a maximum of only 1º versus 2º with NeoSoniX. Additionally, the frequency is ultrasonic (ie, 32,000 Hz for OZil vs 100 Hz for NeoSoniX) (Figure 1).

Torsional ultrasound should only be used with Kelman or angled tips. The oscillatory movement of the tip is amplified at the end, resulting in a side-to-side movement of 0 µm to 100 µm. This is comparable to the longitudinal displacement of a phaco tip with traditional ultrasound.

TORSIONAL VS LONGITUDINAL
The sideways motion of torsional ultrasound is effective 100% of the time, and it does not induce any significant repulsive action. The backward stroke of longitudinal ultrasound has no effect at all, rendering it effective only 50% of the time. Because of the lack of repulsion, the nuclear material seems to be glued at the tip when it is emulsified. Fluid turbulence in the anterior chamber is significantly reduced with torsional ultrasound, because of the almost constant occlusion and the shortened surgical procedure time. Protective viscoelastic substances are better retained, and corneal endothelial cells are better protected.

Very low fluidics settings are effective with torsional ultrasound (Figure 2). With a very low aspiration flow setting of less than 20 mL/min (Figure 3), a bottle height of 50 cm, and a low vacuum setting of less than 250 mm Hg, the efficiency of torsional ultrasound for nucleus emulsification is still amazingly good. In the case of weak zonules, a posterior capsular rupture, or a floppy iris, the greatly reduced fluid turbulence will help to prevent vitreous or floppy iris to be drawn to the phaco tip.

A dispersive viscoelastic, injected to push back the vitreous or iris—or to sequester a nuclear piece to prevent it from falling into the vitreous—will not be aspirated easily. In this way, a safe working distance may be maintained between the phaco tip and vitreous or floppy iris, helping the surgeon to control very difficult situations and prevent complications. The surgeon can feel more confident in handling these complicated cases.

CHALLENGING CASES
Posterior capsular rupture. I have had to deal with remaining nuclear quadrants after an early posterior capsular rupture on several occasions. After stabilizing the situation by injecting Viscoat (Alcon Laboratories, Inc.) behind the nuclear pieces (Figure 4), I always try to bring one quadrant superior to the iris plane with a bimanual technique (ie, injecting Viscoat behind the piece with one hand and using a second instrument to manipulate it centrally and upward into a safe zone above the iris plane). I then introduce the phaco tip underneath the quadrant and emulsify it very slowly and controlled, without washing out the viscoelastic underneath. I use the following settings: (1) 2.2-mm main incision, (2) mini-flared tip plus ultrasleeve, (3) 50-cm bottle height, (4) 15-mL/min linear aspiration flow, (5) 250-mm Hg fixed vacuum, and (6) 70% linear power and continuous torsional ultrasound only.

I bring every quadrant into the safe zone by injecting additional viscoelastic and emulsifying them one by one, without any significant fluid turbulence or pressure drops.

Zonular weakness and floppy iris. For zonular weakness and floppy iris cases, I use similar fluidics settings to minimize fluid streams and pressure variance. I have been able to complete all procedures without any major problems.

Corneal endothelial dystrophy. In corneal endothelial dystrophy cases, I use the following settings: (1) 2.2-mm main incision, (2) mini-flared phaco tip plus ultrasleeve, (3) 75-cm bottle height, (4) 15-mL/min linear aspiration flow, (5) 350-mm Hg fixed vacuum, and (6) 80% linear power and continuous torsional ultrasound only. At the end of quadrant removal, a thick layer of Viscoat is still visible, which reassures me that the endothelial cells are protected during the entire procedure.

Khiun F. Tjia, MD, is an Anterior Segment Specialist at the Isala Clinics, in Zwolle, the Netherlands. Dr. Tjia is the Co-Chief Medical Editor of CRST Europe. He states that he is a research consultant for Alcon Laboratories, Inc. Dr. Tjia may be reached at kftjia@planet.nl.