Improved software function provides vacuum on demand

Barrie, Ontario-The CASE (chamber stabilization environment) component of WhiteStar ICE technology (Advanced Medical Optics) is based on the patented occlusion recognition feature and essentially works to resolve a longstanding issue with phacoemulsification systems-anterior chamber instability and damage associated with postocclusion surge, according to Donald Nixon, MD, of Barrie, Ontario, who was a clinical investigator for this new technology.

WhiteStar ICE is software for the Sovereign phacoemulsification system that offers improved fluidics as well as advanced pulse shaping, and CASE is the fluidics component, Dr. Nixon said.

The Intellisis occlusion recognition monitors vacuum during phacoemulsification and senses when the surgeon will reach occlusion. A time delay is then triggered, followed by a step down to a preset lower vacuum.

"The time in phaco surgery that has the most angst is when we are removing the individual segments, whether we have used a divide-and-conquer technique, a stop-and-chop technique, or vertical chop technique," Dr. Nixon said. "We have these segments that we need to remove. We impale the segment on the phaco needle, and a combina tion of vacuum as well as the phaco energy is used to emulsify that segment. Once you get past the center portion of that segment, there is a point when vacuum is broken. And when vacuum is broken, there is an immediate shallowing to some extent of the anterior chamber environment because there is a built-up vacuum in the tubing system that needs to be neutralized.

"At this point problems can occur, such as the phaco needle coming into contact with the iris or with the posterior capsule. So a lot of trepidation occurs during surgery because of this break in occlusion," he added.

Response to occlusion

Several companies have developed technology to deal with this problem, and AMO's solution is a patented occlusion recognition system, Dr. Nixon said.

"It's fundamental in terms of being able to do something," he said. "If you don't have a system that recognizes when occlusion is occurring, then how can you respond to it?"

The occlusion recognition system has been part of the last several versions of the software, but CASE is a new modification. It addresses the fact that when the occlusion level has been reached, the high vacuum level does not need to be maintained to keep the segment in position, Dr. Nixon explained.

"That's where the CASE system has shown its true advancement," he added. The occlusion recognition system will turn on CASE when a preset maximum vacuum (max vac) level had been reached and maintained. In a surgeon-controlled interval between 100 and 500 msec at or above the max vac, the CASE system reduces vacuum from the peak level, for example 400 mm Hg, to another preset level, such as 250 mm Hg.

The lower level is still sufficient for the surgeon to maintain a grasp on the segment, but because occlusion is broken at 250 mm Hg rather than 400 mm Hg, the amount of stored vacuum is significantly lower, Dr. Nixon said.