Stability of Target IOP in Gravity-Fed Versus Actively Controlled Phacoemulsification Fluidic Systems
Purpose
To compare 3 phacoemulsification fluidic systems in terms of their ability to maintain a target IOP under varying aspiration flow rates.
Methods
The hand piece of each machine was inserted into a small acrylic test chamber containing access ports for pressure measurement. The machines were operated in a traditional gravity feed irrigation mode with bottles of balanced salt solution hanging from an IV pole. One machine was operated in an active control mode. Another machine was operated using pressurized balanced salt solution. Bottle heights and/or bottle/bag pressures were selected to provide equal starting target pressures at zero aspiration flow. Aspiration flow rates were then adjusted across their respective ranges while steady state IOPs were measured in the test chamber.
Results
For all gravity fed systems, measured IOP decreased with increasing aspiration flow regardless of bottle height or starting IOP. This included the system with pressurized infusion. The system with active fluidics maintained the target IOP at all flow rates (within 0.02 mmHg per cc/min), but experienced a slight decrease in IOP at the highest flow rate (maximum drop = 6.0 mmHg).
Conclusion
At equivalent target IOPs, all gravity fed systems, including the one with pressurized infusion, experienced a decrease in IOP as a function of increasing aspiration flow. The system with active fluidics provided a constant steady state IOP across all but the very highest flow rates under test.