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Ramon Carsola Dimalanta, Kevin Miller, Manuel Nicoli; Fluidic Dynamics of Intraocular Pressure (IOP) as it Applies to Gravity-Fed versus Actively-Controlled Phacoemulsification Systems. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1897.
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© ARVO (1962-2015); The Authors (2016-present)
To use fundamental fluid dynamic theory to explain and compare the performance of 3 phacoemulsification fluidic systems in terms of their ability to maintain a target IOP under varying aspiration flow rates.
The hand piece of each machine was inserted into a small, rigid test chamber fitted with access ports for pressure measurement. The machines were operated in a traditional gravity fed irrigation mode with bottles of balanced salt solution hanging from an adjustable pole. One machine was operated in an active control mode. Another machine was operated using pressurized air to augment the pressure within the hanging bottle. 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 pressures were measured in the test chamber.
For all gravity fed systems, measured IOP decreased with increasing aspiration flow regardless of bottle height or starting IOP; following Bernoulli’s equation. 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).
Guided by classic fluid mechanic fundamentals of inviscid fluids, laboratory experiments demonstrated that 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.
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