Managing post-occlusion with advanced fluidics

April 1, 2014

An ophthalmologist compares two currently available fluidics systems and their ability to recover after occlusion is interrupted.

 

Take-Home

An ophthalmologist compares two currently available fluidics systems and their ability to recover after occlusion is interrupted.

Dr. Page

By Lynda Charters; Reviewed by Timothy P. Page, MD

Royal Oak, MI-Minimizing surge during phacoemulsification prevents complications and posterior capsular rupture in the eye during cataract surgery, said Timothy P. Page, MD.

A steady flow state occurs in phacoemulsification with irrigation into the anterior chamber and aspiration through the port. When the occlusion on the phaco tip is interrupted, surge occurs. Irrigation continues during occlusion and causes increased pressure in the anterior chamber, while vacuum continues to draw creating negative pressure to build in the tubing, he explained.

“The dip in IOP after occlusion develops is the point at which the surgeon cannot react fast enough,” said Dr. Page, co-chief, anterior segment surgery and professor of ophthalmology, Oakland University, William Beaumont School of Medicine, Royal Oak, MI. “This is where we have to depend on technology to help prevent complications.”

Dr. Page discussed the results of a Bausch + Lomb-sponsored comparison of two fluidics systems:

  • Infiniti Vision System (Alcon Laboratories) with MicroFlow needle.

  • Stellaris (Bausch + Lomb) Advanced Flow Module Stable Chamber Fluidics System.

Data indicated minimal surge after the occlusion break with the Stellaris system using a 1.8-mm microincisional cataract surgery (MICS) needle and high vacuum settings compared with the Infiniti system.

An advantage of the Stellaris system is that the processor is faster than that of the Infiniti system and recovers faster after surge, which stabilizes the anterior chamber more quickly.

In another look at recovery from surge using a 0.3-mm irrigation/aspiration handpiece, the system had minimal surge compared with the Infiniti system as indicated by the more gradual pressure change of the Stellaris system.

“These outcomes are significant to procedural safety because faster recovery from surge minimizes the chance of posterior capsule breaks and vitreous breaches,” he said.

 

Importance of stability

“Stability matters,” Dr. Page said. “The stability of the anterior chamber affects the movement of the posterior capsule forward toward the phaco tip.”

In a study (Am J Ophthalmol. 2008;145:1014-1017) performed in cadaver eyes in which the same two systems were compared, the surge following occlusion was significantly (p < 0.0001) reduced with the Stellaris system compared with the Infiniti phaco system, he noted.

Dr. Page offered this pearl to prevent post-occlusion surge during MICS-lowering the fluidic settings by decreasing the vacuum levels and aspiration flow rates to decrease the amount of post-occlusion surge.

Study materials from the American Academy of Ophthalmology’s ONE Network also suggested that lowering the vacuum by about 100 mm Hg to aspirate the final nuclear fragment-which is the time at which surge is likely to occur-can help reduce the risk of surge, he noted.

“This is something I had been teaching my residents for the past 7 to 8 years,” Dr. Page said. “However, since I switched to the venturi-based [system], I no longer have to use this practice.”

A number of system features help combat surge: the stiff tubing, the flow restrictor in the needle, the low dead volume in the fluidics system and sensor, and the high central processing unit frequency.

 

 

Phaco tip design

Feature of the phaco tip design contribute to stability. In addition to the 0.5-mm internal diameter that restricts flow through the needle, the hourglass design helps prevent lens particles from clogging the tip and serves as a second cavitation surface.

“The hourglass tip provides a forward-facing cavitation area for emulsification so that particles do not clog the small internal diameter,” Dr. Page said.

In addition, the tip provides a larger holding area while maintaining a small internal diameter, and directs inflow of particles to the center of needle, which reduces chatter, he explained.

After having performed about 1,200 cases with the Stellaris system, Dr. Page said he has not had any posterior capsule ruptures resulting from post-occlusion surge since switching to venturi-based fluidics.

Post-occlusion surge during phacoemulsification must be minimized to prevent surgical complications and ocular damage, he said.

“Studies and personal experience have shown minimal to no surge after occlusion break with the Stellaris system using a 1.8-mm MICS needle and high vacuum settings,” Dr. Page concluded. “The fluidics on the system prevent post-occlusion surge and provide excellent chamber stability, improving the safety of cataract removal and clean-up during challenging cases.”

 

Timothy P. Page, MD

E: tpagemd@yahoo.com

Dr. Page is a consultant to Bausch + Lomb.