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

Purpose: To compare the fluidics of different phaco tip designs: straight, flared and balanced, across 2 orthogonal planes centred on tip aperture, at the aim of inferring lens fragments attraction and repulsion determined by sheer 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 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 mode.