Chamber stability in modern cataract extraction
Dr Randall Olson looks at the results of head-to-head testing of the latest phacoemulsification machines.
Key Points
The ability to maintain a stable anterior chamber during phacoemulsification is a key element of modern cataract extraction. All of the devices in the latest generation of phaco machines offer fluidics controls that greatly improve the ability to keep the chamber stable. Nevertheless, there are differences in how these devices perform, especially under challenging conditions.
Over the past few years, my colleagues and I have been looking for ways to objectively compare the phaco machine fluidics. In early 2007, we published an article comparing four phaco machines that were available at that time1 . More recently, we have been studying the differences among the latest-generation machines: Alcon Infiniti; Bausch & Lomb Stellaris; and AMO WhiteStar Signature. These latest results, which I discuss in this article, were published in the June 2008 issue of AJO2.
Vacuum and flow accuracy
Given our previous research, it was not surprising to find that machine-indicated vacuum levels differed significantly from the actual vacuum at the tip during occlusion.
With the bottle height at 60 cm, we recorded the actual tip vacuum when the machines indicated that vacuum was at 100, 200, 300, 400, 500, and 550 mmHg.
On average, the actual vacuum of the Stellaris device was 6.8% higher than indicated by the machine. Actual vacuum of the Infiniti and WhiteStar Signature systems was 1.9% and 7.8% lower, respectively, than indicated by the device.
Next, we wanted to test the accuracy of the machine-indicated aspiration and determine how much vacuum was required to maintain a given aspiration rate. We set all the systems for maximum vacuum of 550 mmHg and flow of 60 mL/min with the bottle height at 60 cm. We measured the actual aspiration rate for 60 seconds at a time, repeated 10 times.
