Quantifying Phacoemulsification Handpiece Repulsion as a Function of Tip Design: A Particle Image Velocimetry Study

INTRODUCTION: The aim of this study was to compare the fluidics of different phaco tip designs: straight, flared, and balanced, across 2 orthogonal planes centred on the tip aperture, with the aim of inferring lens fragment attraction and repulsion determined by shear fluid motion. METHODS: Phaco handpiece of Virtuoso (BVI) longitudinally drove straight and flared tips, while Centurion (Alcon) drove balanced tip in longitudinal, torsional, and combined modes. Tests were run into a Plexiglas chamber filled with balanced salt solution with neutrally buoyant particles, and particle image velocimetry analysis was performed at 6,250 frames per second. RESULTS: BSS velocity increased with stroke length and was significantly higher for the balanced tip longitudinal stroke (p < 0.01). At 90% ultrasound power, the balanced tip generated significantly higher BSS velocities than the straight and flared tips, both in longitudinal, purely torsional, and combined motion (p < 0.05). Aspiration significantly altered BSS velocities in all tested tips (p < 0.05 for all), increasing attraction. Straight tips showed the lowest BSS velocity at all stroke lengths (p < 0.01); balanced tip in torsional mode had the second highest BSS velocity (after the same tip in longitudinal mode) across the vertical plane. CONCLUSION: Straight tips in longitudinal mode determine significantly lower fluid velocity in a test chamber than flared and balanced tips operating in longitudinal, torsional, and combined modes.