Surgeons want more predictable phaco outcomes

June 1, 1999

Cataract surgeons are enjoying the evolution of phaco technology, which is making procedures safer and quicker. Phaco systems have been equipped with new power modes, features that offer greater control of intraocular conditions and increased efficiency, all of which add up to a new generation of advanced phaco techniques.

Sovereign

The Sovereign (Allergan, Irvine, Calif.) merges the advanced high vacuum fluidics of the AMO Prestige unit (Allergan) with the burst and occlusion mode programmability of the AMO Diplomax (Allergan). Surgeons with Sovereign experience were impressed by the machine’s power, programmable settings, fluidics, ease of use and setup.

The Sovereign has an on-board fluidic computer that allows the pump to rotate forward and backward, which helps surgeons to control the release of vacuum. The machine has several settings for pre- and post-occlusion, four phaco modes and four memory modes. The four power modes allow surgeons to have continuous mode phaco, pulse, power pulse and burst mode. Surgeons can use different combinations of memory to disassemble different types of cataracts.

The small, lightweight, ergonomic handpiece has four crystals allowing for short, long, multiple and continuous bursts, in addition to an on/off burst that can be as short as 20 msec.

David F. Chang, MD, used the Sovereign to perform both the classic Nagahara and the Pfeifer Quick Chop variations of phaco chop on a series of 12 brunescent nuclei. “Both of these techniques allow us to decrease phaco power and time because we are substituting manual energy for ultrasound energy in the disassembly of the nucleus. We can decrease stress on the capsule and zonules because the manual forces of one instrument pushing against the other are directed centrally inward, rather than outward toward the capsule,” Dr. Chang said.

“Phaco chop of dense nuclei is facilitated by achieving a solid purchase of nuclear segments with the phaco tip. This stabilizes and anchors the nucleus during chopping and creates enough holding force to elevate chopped pieces out of the tight confines of the capsular bag. With the Sovereign, solid purchase of nuclear segments was consistently achieved through the combination of burst mode, very high vacuum settings and rapid vacuum rise time obtainable through occlusion mode programmability,” he said.

Burst mode, although inappropriate for a soft nucleus, is very useful for dense nuclei. In these lenses, it is difficult to keep the tip tightly embedded and occluded. Burst mode impales the nucleus with single burst strokes that maintain a tight seal around the tip. Vacuum settings of up to 350 mm Hg (19-gauge tip) and 400 to 450 mm Hg (20-gauge tip) provided excellent holding force with a stable chamber, according to Dr. Chang.

The Sovereign cuts very efficiently at power levels as low as 5% for average nuclei. Low power levels decrease the stroke length of the phaco tip, reducing chatter and the amount of heat generated. Because of this, Dr. Chang said, the average equivalent phaco time for these 12 nuclei was 12.5 seconds (range of 8 to 21 seconds) using phaco chop.

“We found the Sovereign to be significantly better than any other system we were using,” said Pierre Faber, MD. “The cutting of this machine is outstanding, smooth and powerful.” Dr. Faber evaluated the performance and reliability of the Sovereign and was impressed by the machine’s fluidics.

“The system [Sovereign] seems to know when occlusion is happening, knows when occlusion is breaking, so there are no surges,” Dr. Faber said. “The chamber is always deep, there is no flattening of the chamber, very little or no iris flutter, smooth cortical cleanup and disassembly, and it is very easy to remove the epinucleus.”

Concentrix pump versatility

---The Concentrix can either replace or coexist with the Millennium’s Venturi module.

The Millennium’s Concentrix technology (Bausch & Lomb Surgical, St. Louis, Mo.) is the only machine to offer the ability to switch between flow-based (peristaltic like) and vacuum-based (Venturi like) memory settings to best match each step of a cataract procedure. The Concentrix Fluidics Control Technology is based on the scroll pump, which consists of two scroll-shaped components. The female scroll consists of a groove that is stationary. The male scroll fits inside the female and goes through an orbital motion to create the vacuum and flow characteristics of the pump. Fluid from the handpiece passes through a vacuum sensor adjoining to the scroll elements. This sensor creates a feedback loop to the computer that controls the pump’s speed and direction to give priority to either the flow-based emptying phase or the vacuum-based filling phase of the pump’s cycle, and create either peristaltic or Venturi like responses. Surgeons then can establish individual memory settings for each step of a procedure and program flow-based or vacuum-based modes to maximize the safety and efficiency of the surgery.

“If we were doing a divide and conquer technique, we might use a flow mode for sculpting to give us precise flow when working near the capsule,” said Terence M. Devine, MD. “Then we might switch to a vacuum mode to draw out the quadrants. I think that most surgeons that have used the machine agree that a Venturi type of vacuum response works best for removing cortex. But for capsule polishing, a flow mode is probably better.” According to Dr. Devine, vacuum mode is most effective in removing viscoelastics.

The advantages of the Concentrix Fluidic Control Technology are the simultaneous control of fluidics and ultrasound with the Dual-Linear Footcontroller, and the ability to switch back and forth between flow modes or vacuum modes during a single case. “When we combine Concentrix with the Dual-Linear Footcontroller, I think we gain the benefit of total control of fluidics with more surgical options,” Dr. Devine said. “And in the 9 months or so that I’ve been using this technology, it has translated into better safety and shorter case times.”

Infusion capacity improvement

---The Alcon Accurus. Pressurized infusion system eliminates the need for infusion bottle elevation.

The Accurus 600DS (Alcon, Fort Worth, Texas) is an efficient phaco machine that has demonstrated ultra-rapid nucleus removal while chambers remain stable, according to Richard J. Mackool, MD. The Accurus is a Venturi system with aspirated fluid drain and vented gas force infusion, which creates an incredible improvement in infusion capacity, according to Dr. Mackool.

“In my opinion, vented gas force infusion is better than gravitational infusion,” Dr. Mackool said. “It gives more of a consistent chamber depth, and it is not affected by bottle volume and resistance to air flow by the bottle spike vent.”

Although conventional gravity feed has been the standard, Dr. Mackool said it is not the best because of the resistance to atmospheric air flow into the infusion bottle. The more fluid in the bottle, the harder it is for the air bubble to get to the top, therefore when the bottle is full, it is difficult to get maximum infusion capacity. When the bottle becomes less full, infusion capacity improves. Vented gas force infusion provides reliable infusion with constant pressure, regardless of bottle volume.

The aspiration cassette of the Accurus has a tiny 16-cc air space and fluid is maintained at a constant level in the cassette by a peristaltic vacuum system that drains the cassette when an optical sensor detects an elevation of the cassette fluid level. There is a consistent rise time from beginning to end of cases, according to Dr. Mackool, because the volume of air in the cassette remains constant.

Efficiency in sculpting the nucleus was affected by needle design and diameter, especially with regard to sculpting efficiency in hard nuclei. The nucleus was removed at a rapid rate without increased risk of chamber collapse or trauma to the posterior capsule and/or iris.

---The Kelman-Mackool ABS Flare Tip.

“The Accurus Venturi aspiration system achieves remarkable levels of aspiration efficiency and nuclear followability,” Dr. Mackool said. “[There is] great efficiency because of in creased nuclear attraction, increased holdability, rapid nucleus removal and the most stable chambers you could ever imagine. The phaco tip remains in the safe control zone, and there is maximal thermal protection with the Mackool ABS flare tip.”

Series 20000 Legacy

The Series 20000 Legacy (Alcon) represents one of the new generations of phacoemulsification systems that debuted during the mid-1990s and has since been updated.

With respect to fluidics, it has a pump system called TurboStaltic pump that is a very smooth system, according to I. Howard Fine, MD. “It has a floating head so there are no pulsations as the pump speed and vacuum build-up takes place. It has non-compliant fluidic channels to allow for higher vacuum with fewer pulsations,” he said.

“The tubing in the cassette has been replaced with rigid plastic fluidic channels that are totally non-compliant. This allows us to have a high-vacuum system with less surge. The new high-vacuum tubing allows us to use extremely high vacuums that were previously considered unsafe,” Dr. Fine said. “The ultrasonic generator is a four crystal system, which is extremely powerful.”

The Legacy has constant admittance tuning, allowing for continuous feedback and re-tuning on a rapid, ongoing basis. This compensates for changing density and configuration of nuclear material at the tip in order for the system to work at its maximum efficiency.

Alcon has recently enhanced the software, what they call the performance option package. This software package expands the number of ultrasound modes and the different ways in which phaco energy can be delivered. “It has added enormously sophisticated power modulations,” Dr. Fine said. “In the package, they have added not only burst mode, but variations of burst mode, such as single burst mode, programmable intervals between bursts, as well as durations of bursts. In pulse mode, what we have is a distribution of on/off with equal periods of on and off. When I’m in pulse mode, I usually use two pulses per second, which means I get 250 msec of power, 250 msec on, 250 msec off.” Users have a fixed interval of power and a fixed interval of pause between power while constant vacuum is ongoing. The vacuum holds, but surgeons will have the ability to vary power.

In burst mode, we have panel control of power. When the foot pedal is pressed on foot position 3, the interval between bursts of power can be varied. The further the foot pedal is pressed, the shorter the interval is between bursts. Burst mode is best used for lollipopping or impaling the nucleus and to evacuate nuclear material following chopping.

For Your Information:

• David F. Chang, MD, can be reached at 762 Altos Oaks Drive, Ste. 1, Los Altos, CA 94024; (650) 948-9123; fax: (650) 948-0563. Dr. Chang has no direct financial interest in any of the products mentioned in this article. He is a paid consultant for Allergan.
• Terence M. Devine, MD, can be reached at RD 2 Box 184E, Athens, PA 18810; (570) 888-5858; fax: (570) 882-3411. Dr. Devine has no direct financial interest in any of the products mentioned in this article. He is a paid consultant for Bausch & Lomb.
• Pierre Faber, MD, can be reached at 616-2525 Willow St., Vancouver, British Columbia V5Z 2NB; (604) 879-0203; fax: (604) 879-9976. Dr. Faber has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• I. Howard Fine, MD, can be reached at 1550 Oak St., Ste. 5, Eugene, OR 97401; (541) 687-2110; fax: (541) 484-3883. Dr. Fine has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• Richard J. Mackool, MD, can be reached at 31-27 41st St., Astoria, NY 11103; (718) 728-3400; fax: (718) 728-4882. Dr. Mackool has a direct financial interest in the Mackool System. He is a paid consultant for Alcon.