spotlight on technology & technique
Surgery Without Surge
Users report that STAAR's Cruise Control device makes phaco safer without compromising efficiency.
By Christopher Kent, Senior Associate Editor

One of the issues all cataract surgeons must deal with during phacoemulsification is the possibility of surging when an occlusion at the tip breaks. (Under normal conditions, a standard 19-gauge phaco tip used with a vacuum setting of 400 mm Hg can generate a surge as high as 300 cc/min, putting chamber stability at risk.) Of course, it's possible to lessen the danger by adjusting settings or using a smaller phaco tip, but these changes also reduce efficiency.

Over the years a number of design improvements from different manufacturers have lessened the potential for surge, but most have necessitated some kind of trade-off. For example, reducing the diameter of the tubing helps, but this also increases the likelihood of stagnation and occlusions in the tubing.

In contrast, a device from STAAR Surgical, called "Cruise Control," uses a specially designed filter to limit surge, regardless of vacuum setting, the size of the phaco tip or the diameter of the tubing. As a result, the occurrence of surge is minimized -- without undercutting efficiency.

How It Works

Cruise Control's internal filter keeps the flow restriction orifice from clogging.

Cruise Control is a single-use cylindrical device placed between the phaco handpiece and the aspiration tubing. The internal filter, which has a large surface area to prevent clogging, captures and retains all cataract material removed from the eye during phaco. (See diagram, left.) Meanwhile, the fluid, after passing through the filter, must pass through a small orifice the size of an I/A tip that leads to the aspiration line. This small passageway causes non-linear flow restriction, keeping the flow rate from rising above 50 cc/min. (Flow below 40 cc/min is unaffected.)

This combination is effective because the filtering prevents the flow-restricting orifice from becoming clogged. The filtering also keeps the inside of the tubing clean longer (an advantage if you prefer reusable tubing) and prevents material from accumulating inside the machine.

As a result of the flow restriction, the surgeon can use a large phaco tip and work at high vacuum without endangering chamber stability. Best of all, Cruise Control is designed to attach to the aspiration line of any phaco machine, so the benefits are available to any cataract surgeon.

Feedback From the Field

Steven N. Montgomery, M.D., who practices in Las Vegas, Nev., says that using Cruise Control has made a big difference. "Chamber stability is greatly improved and control at various levels of vacuum is enhanced. There is significantly less flux, and occlusions have been eliminated.

"The patient benefits as well," he notes. "It's most notable in post-vitrectomy patients. I experience significantly less iris movement and ciliary body rotation by eliminating surges, which makes the patient more comfortable.

"Cruise Control has improved my surgical time and definitely increases safety and comfort for the patient. It does add an additional expense per case to the cost of the surgery, but it's money well spent.

"In fact," he adds, "all of the partners here at Shepherd Eye Center use it. These days we don't do phaco without it."

	The Cruise Control device attaches to the aspiration line of any phaco machine.

Putting It to the Test

Two surgeons we interviewed have done studies comparing surgery with and without Cruise Control. The first compared surgery with all parameters kept the same; the second compared them while taking advantage of the higher vacuum permitted by the Cruise Control device. (In both studies, eyes with complicating factors such as small pupils were excluded.)

Paul S. Koch, M.D., chief medical editor for Ophthalmology Management, compared energy and time usage when performing nucleus emulsification and cortex aspiration with and without Cruise Control. "Our study included 100 cases -- 50 in each format," he explains. "The two groups were essentially identical, with a mean nuclear density of 2.33 in the Cruise Control group and 2.32 in the control." Because the surgeon knew when Cruise Control was being used, Dr. Koch timed the other steps of the operation to be sure that all cases were consistent in technique. Vacuum setting was identical for both groups.

"We found a statistically significant difference between the two groups," he says. "Effective ultrasound energy used for I/A was 4.69 with Cruise Control, but 6.80 without it. And although we didn't find the difference in I/A time that we expected, we did document a small but statistically significant difference in total case time. Cases with Cruise Control averaged 261 seconds; the others averaged 277.3 seconds."

Dr. Koch found no statistically significant differences between the two groups in any other part of the surgery, so the two groups had essentially identical surgery, except for the use of Cruise Control in half the patients.

The bottom line? Using Cruise Control resulted in a 31% reduction in ultrasound energy during segment removal and a 5.8% reduction in total case time.

David Brown, M.D., who practices in Fort Myers, Fla., conducted a similar study involving 78 cataracts. However, he used a Venturi vacuum setting of 220 mm Hg when doing surgery without Cruise Control -- and 350 mm Hg with Cruise Control. The "phaco flip" technique was used in all 78 cases, and ultrasound power and bottle height were the same for both groups -- 80% and 100 cm, respectively.

As expected, the Cruise Control group maintained stable chambers, with no occlusions or sudden decompressions. Neither group had any operative complications or unusually high IOP at 24 hours post-op. But other differences were significant:

• Grade-2 nuclei required an average of 0.277 minutes of ultrasound time at the lower vacuum, but only 0.239 minutes with the higher vacuum and Cruise Control. Also, at 24 hours post-op, 23% of eyes in the former group showed evidence of corneal morbidity, while only 10% of the Cruise Control group did.
• Grade-3 nuclei averaged 0.598 minutes of ultrasound time at the lower vacuum, but only 0.282 minutes with the higher vacuum and Cruise Control (less than half the time). And at 24 hours post-op, 63% of grade-3 eyes operated on at the lower vacuum showed evidence of corneal morbidity. Only 22% of the Cruise Control group did.

Putting It in Perspective

"Using the Cruise Control device has a number of significant advantages," says Dr. Brown. "First, and most important, it protects against negative surge and penetration of the posterior capsule.

"Second, it shortens the surgical time required for ultrasound and irrigation and aspiration. This means less trauma to the eye, less surgical risk, and an improvement in overall surgical time.

"Third, it lets the surgeon use ultrasound power more efficiently. Using Cruise Control with soft cataracts I can maintain low power but increase the vacuum level with confidence. Conversely, managing a hard cataract requires high power and high vacuum, and this is much less risky with Cruise Control.

"I'd recommend the Cruise Control to all surgeons," he adds. "Even with consistent improvements in phaco machine fluidics and flow restrictors in ultrasound tips, the Cruise Control smoothes out the hydrodynamics in the anterior chamber and synergizes the variations in power and vacuum that different clinical situations require."

For more information about the Cruise Control filter, contact STAAR Surgical at (800)352-7842, or visit www.staar.com.