Filtering device decreases aspiration rate in two phaco systems

Key Points

Salt Lake City-A filtering device (Cruise Control, STAAR Surgical Co.) placed between the phacoemulsification handpiece and aspiration tubing increases the stability of the anterior chamber during phaco because it decreases the post-occlusion aspiration flow rate in two venturi systems (Legacy 20000, Alcon Laboratories; Millennium venturi, Bausch & Lomb). Changes in bottle height and flow minimally affect surge in another system (Millennium peristaltic, Bausch & Lomb), and surge decreases with increased bottle height and decreased aspiration rate in another system (Infiniti, Alcon), according to Matt Ward, a medical student at the University of Utah, Salt Lake City. He made a presentation at the most recent annual meeting of the American Society of Cataract and Refractive Surgery on behalf of Dan Georgescu, MD, PhD, Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah.

"Surge is a function of elastic recoil inherent in compliant tubing in phacoemulsification systems that can injure or displace structures in the anterior chamber," Ward said. "Surge can be minimized by either decreasing compliance or increasing resistance in the system through a variety of means."

"We measured flow rates by collecting fluid after 1 minute of continuous irrigation/aspiration with and without [the filtering device]. We measured surge by inserting phaco tips through scleral tunnel incisions and glued the incisions shut using cyanoacrylate," he said. "We simulated occlusion by clamping the aspiration line and simulated surge by releasing the clamp at the maximum volume level." Changes in the anterior chamber depth were assessed by evaluating real-time video recordings of A scan tracings.

"The results of [filtering] and flow in the [two] venturi machines indicated that aspiration rates were significantly decreased by cruise control. The change in aspiration was more marked in the Millennium machine," according to Ward.

Using 500 mm Hg vacuum and 75 cm bottle height, the filtering device decreased the aspiration rates by 40.2% (93.1 ± 2.8 mm to 55.7 ± 1.1 mm) (p <0.01) in the Millennium venturi machine and 11.7% (38.9 ± 0.2 mm to 34.3 ± 0.2 mm) (p <0.01) in the Legacy machine, he said.

"The surge was also decreased by [the filtering device], with a more dramatic effect in the Millennium venturi machine," he said.

The filtering device decreased surge by 78.6% (1.0 ± 0 mm to 0.214 ± 0.020 mm) (p <0.01) in the Millennium venturi machine and 42.9% (0.09 ± 0.02 mm to 0.05 ± 0.00 mm) (p <0.01) in the Legacy machine.

Bottle height and surge

In the bottle height and surge experiment, which used a fixed aspiration rate of 12 mm per minute, the investigators found a significant linear decrease in the Infiniti machine with increased bottle heights. In the Millennium peristaltic machine, surge was constant across changes in bottle height, Ward reported.

When the investigators increased flow at a fixed bottle height, they found a linear increase in surge in the Infiniti machine across all aspiration rates evaluated. He reported that the Millennium peristaltic machine seemed to be independent of increased aspiration rates.

"[The filtering device] decreases post-occlusion surge and aspiration flow in the [two] venturi systems, with more dramatic changes in the Millennium venturi machine," he said. "Changing bottle height and flow has minimal effects on surge in the Millennium peristaltic system. Surge decreases linearly with increasing bottle height and decreasing aspiration rate in the Infiniti system."