By Dr. Terry Kim, MD [Medrounds Profile]

“If you question the additional benefits of the IP software, I highly recommend that cataract surgeons give it a trial.  During cataract surgery on a dense lens, such as a 3+ nuclear sclerotic cataract, divide the nuclear material into four quadrants using your usual technique of divide and conquer, prechop, or chop. Then, go ahead and emulsify the first two quadrants using 100% torsional ultrasound without IP activated. When you’re finished, simply turn IP on with the touch of a button on the screen and emulsify the last two quadrants with IP activated.  You will be able to see and feel the difference in terms of the enhanced efficiency in lens removal.”  OZil IP represents an advance in the management of phaco energy where short pulses of longitudinal ultrasound are automatically added to OZil torsional ultrasound when a preset vacuum threshold is met. This feature enhances OZil ultrasound by keeping the lens material at the ideal shearing plane of the phaco tip and increasing followability by not allowing occlusion of the phaco tip to occur.  As a result, the IOP fluctuations in the eye are reduced and post-occlusion surge is essentially eliminated.  The software automatically manages this ultrasound power modulation so that it becomes a smart, seamless event with minimal effort from the surgeon.

“OZil was a major advance in ultrasound  technology where the side-to-side shearing motion of the phaco tip, as opposed to traditional front-to-back motion of longitudinal ultrasound, was found to be much more efficient in phacoemulsification by reducing repulsion of lens material, improving followability, and stabilizing the anterior chamber.  The OZil IP software accentuates the efficiency of this OZil platform by eliminating the need to “blend” in longitudinal ultrasound and by automatically adding in short pulses of longitudinal energy only when needed, which becomes clinically applicable not only in routine cases but also in denser lenses and other complex phaco cases.”

I recommended using the OZil IP default settings to start, although they are customizable as the surgeon becomes more comfortable with the technology. For the majority of cases, I use the default OZil IP settings of 95% vacuum threshold, phaco pulse on time of 10 ms, and a longitudinal/torsional ratio of 1.0.  With my phaco settings of 100% linear torsional and 0% longitudinal ultrasound power, 350 mm Hg vacuum limit, 35 mL/min of aspiration flow rate, and a bottle height of 95 cm H2O, each activation of the OZil IP mode will deliver twenty 10 ms-long pulses of longitudinal ultrasound (for a total of 200 ms) every time the vacuum exceeds 332 mm Hg (95% of 350 mm Hg) to ensure that maximum vacuum is not reached and the phaco tip never fully occludes.  OZil IP counter will reset when the vacuum drops below the preset vacuum threshold (i.e., 332 mm Hg with my settings) or when the foot pedal moves out of foot position 3, regardless if the full 200 ms of cumulative longitudinal ultrasound has been delivered.  In addition, OZil IP will deactivate if 200 ms of OZil has already been delivered and the vacuum level does not drop below the preset vacuum threshold, in which case the surgeon has to move the foot pedal out of foot position 3 to reactivate OZil IP.  However, this would only be necessary when encountering an exceptionally dense nucleus.  “All of this essentially translates to increased phaco efficiency with more stable anterior chambers.  OZil will be a no-brainer for routine cases but will be a helpful attribute for the more complex cases that involve denser lenses, shallow anterior chambers, loose/brittle zonules, and small pupils.  In all of these scenarios, you want to maximize the efficiency of your phacoemulsification, minimize the turbulence in the anterior chamber, decrease the stress on the capsule, zonules, and iris, and reduce the trauma to the corneal endothelium.”  With the Alcon Infiniti unit, the surgeon has the opportunity to customize virtually every setting, including the advanced settings for OZil IP.  This includes changing the vacuum threshold, the pulse on time, the longitudinal/torsional ratio, and/or the minimum threshold settings.  The goal of all of these adjustments is to enhance OZil torsional ultrasound based on the surgeon’s particular phaco settings and techniques.  The vacuum threshold could be set at 90%, for instance, so that OZil IP could be activated sooner (i.e., every time the vacuum exceeds 315 mm Hg given a vacuum limit of 350 mm Hg).  The pulse on time simply determines how many pulses will be required to reach 200 ms, so that a shorter pulse on time will require more pulses to reach 200 ms and vice versa (i.e., a 5 ms pulse on time will require 40 pulses to reach 200 ms while a pulse on time of 20 ms will require 10 pulses to reach 200 ms).

References

1.    Berdahl JP, Jun B, DeStafeno JJ, Kim T. Comparison of a torsional handpiece through microincision versus standard clear corneal cataract wounds. J Cataract Refract Surg. 2008;34(12):2091-5.

2.    Titiyal JS, Ghatak U, Sharma N. Comparison of Phacoemulsification using Torsional Ultrasound (OZil) with and without Intelligent Phacoemulsification. Poster presented at: The AAO Annual Meeting; October 18, 2010; Chicago, IL.