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Optimizing Phacoemulsification Fluidic Settings

Updated: Apr 12, 2021

The function of the phacoemulsification fluidics is to balance the inflow and outflow of fluid in order to maintain the working space, bring cataract material to the Phaco tip, and prevent collapse of the eye. Optimizing the Phaco fluidic settings is crucial to maximizing efficiency and safety of phacoemulsification surgery.

Phaco Machine

In order to optimize the phaco fluidic settings, it is important to match the machine parameters to the surgeon’s phaco technique. With a typical peristaltic phaco machine platform, the most common type in the United States, only a few parameters are adjustable. These include needle size, bottle height, flow rate, and maximum vacuum level.

The selection of phaco needle size is of great importance. The most common sizes are the smaller-bore 0.9‑mm needle and the larger-bore 1.1-mm needle. If the surgeon’s preference is a quicker procedure with rapid nucleus removal, then the larger 1.1‑mm needle size is desirable because it will give a significantly greater flow rate. If the surgeon prefers a slower but more controlled procedure, then the smaller-bore 0.9-mm needle is more suited to that technique. The holding power of the phaco probe on to the cataract nucleus is related to the vacuum level used as well as the surface area of occlusion. Using a larger phaco needle allows for lower vacuum levels to achieve holding power as required in phaco chop techniques.

The bottle height determines the inflow of fluid into the eye. In order to help prevent surge, it is important to keep the inflow of fluid at least as high as the outflow of fluid at all times, because any excess inflow will pressurize the eye and leak from the incision until equilibrium is achieved. The inflow of fluid comes from only 1 source, the bottle of balanced salt solution, while the outflow of fluid comes from 2 sources, the suction via the phaco needle and the leakage from the incisions. If, at any time, the outflow outstrips the inflow, the eye will collapse and there is a high likelihood of posterior capsule rupture. It is often advantageous to start with a high bottle height to ensure a sufficient inflow of fluid, and then to taper it downwards to minimize the posterior displacement of the lens-iris diaphragm due to the infusion pressure.

phaco machine setting
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For the “phaco chop” method, the holding power of the needle tip is important in order to fixate the nucleus securely while using the chopper to disassemble the nucleus mechanically. This requires a relatively high vacuum, such as 200 to 250 mmHg with the 1.1 mm needle, or 300 to 400 mmHg with the 0.9 mm needle. Once the nucleus has been broken into smaller fragments, the peristaltic flow rate determines the speed at which the fragments are attracted to the phaco tip, with a flow rate of 20 cc/min being very slow and 50 cc/min being very fast. During phaco chop, the surgeon can use the same vacuum and flow rate settings for the entire nucleus removal procedure.

For divide-and-conquer phaco, there are 2 distinct stages of nucleus removal: sculpting of the nucleus and quadrant removal. Different fluidic settings are required for each. For grooving and sculpting of the nucleus, the work is being done by the ultrasonic energy and thus the flow and vacuum settings are quite low—just enough to aspirate the nuclear material removed from each forward stroke of the phaco probe. A vacuum level of less than 100 mmHg and a flow rate of less than 30 cc/min are sufficient for this purpose. For quadrant removal, a moderate amount of holding power is required to bring each quadrant into the phaco tip. Using a higher vacuum level of 200 to 300 mmHg and a flow rate of 30 to 50 cc/min, depending on the needle size, is typically sufficient for this purpose.

With knowledge of the concepts behind the variables, it is easy to tailor the fluidic settings to the surgeon and technique. Understanding the concepts behind the phaco fluidic settings is instrumental in optimizing the parameters for increasing the efficiency and safety of the surgeon’s phaco technique.

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