Experimental anterior chamber maintenance in active versus passive phacoemulsification fluidics systems.

PURPOSE To evaluate the ability of phacoemulsifiers with active versus passive infusion fluidics control systems to maintain target intraocular pressures (IOPs) under varying flow conditions. SETTING Alcon Research, Ltd., Lake Forest, California, USA. DESIGN Experimental study. METHODS An acrylic test chamber was used to model the anterior chamber of the eye. Two passive (gravity-based) systems were tested using bottle heights yielding infusion pressures of 41, 75, and 109 cm of water under zero-flow conditions. One actively controlled system was tested using equivalent target IOPs of 30, 55, and 80 mm Hg. Test chamber IOPs were measured at aspiration flow rates of 15, 30, 45, and 60 cc/min. RESULTS The measured flow rates were similar between fluidics systems across the range of intended aspiration flow rates. All systems achieved the desired target IOPs under zero-flow conditions. After activation of aspiration flow, however, measured IOPs decreased from target IOPs for the 2 passive systems. Each 15 cc/min increase in the aspiration flow rate produced a pressure drop of 14.0 to 16.2 mm Hg or 9.3 to 14.2 mm Hg, depending on the system. Measured IOPs in the actively controlled system closely matched the targeted IOPs across all tested aspiration flow rates, deviating from targets by no more than 4.3 mm Hg. CONCLUSIONS All phacoemulsification aspiration infusion fluidics systems achieved target IOPs under zero-flow conditions. Only the actively controlled system maintained target IOPs across a range of aspiration flow rates. These experimental findings suggest that anterior chamber stability might be better in the clinical setting using an actively controlled system. FINANCIAL DISCLOSURE Dr. Dimalanta is an employee of Alcon Research, Ltd. Dr. Miller is an investigator and speaker for and a consultant to Alcon Laboratories, Inc. Dr. Nicoli has no financial or proprietary interest in any material or method mentioned.