December 10, 2013
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BLOG: What you need to know about forced infusion vs. gravity feed irrigation in phaco surgery

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Read more from John A. Hovanesian, MD, FACS.

In this issue of Ocular Surgery News, our cover story addresses phaco fluidics and the benefits some surgeons advocate of forced infusion of balanced salt solution. There are two schools of thought on this:

Pressure provides stability. The first school of thought, belonging to surgeons who use forced infusion, is that pressurized infusion (with pressure provided either by the phaco machine pump or through a pressurized gravity-fed bag or bottle) yields more complete filling of the anterior chamber, which gives greater stability of the posterior capsule. This allows phaco to be performed with intermittently high vacuum, removing epinuclear fragments with less ultrasound energy. Pressurizing the anterior chamber allows more “followability” of lens fragments and requires less vacuum from the phaco machine to achieve a high pressure differential.

The challenge with this approach is that it works best if there is a completely sealed system. In the eye, if we have leakage of fluid around the phaco tip or through a side-port incision, as we often do when performing two-handed techniques, there is the potential for excessive fluid egress. This can defeat the purpose of the forced infusion, reduce the pressure differential and cause unnecessary consumption of balanced salt solution and trauma to the corneal endothelium through fluid turnover. And we know that endothelial loss in phaco surgery is most closely correlated with fluid use, even more than with total ultrasound time.

Control, not pressure. The second school of thought is to use passive balanced salt solution infusion and control closely aspiration and ultrasound. This is my personal favored approach, and I argue for this in the “Point-Counter” that accompanies the cover story. Advocates of this approach claim that excessive volume (and balanced salt solution use) can be avoided when the surgeon has adequate control of aspiration and phaco power. Personally, I favor a phaco system that separates control of ultrasound from vacuum using a dual linear foot pedal. This is a highly versatile approach, especially when paired with a Venturi pump system, which gives very responsive control of vacuum rather than aspiration flow. It’s compatible with microincision cataract surgery just as well as a forced infusion approach. And because infusion is not pressurized and the exiting fluid is through a small-port needle, fluid turnover is quite acceptably small.

In the ever-evolving world of phaco technology, we can perform safer and safer surgery. I strongly encourage readers to review the cover story in this issue of OSN, as there’s no question a better cognitive understanding of phaco fluidics yields safer surgery for our patients.