Fluid dynamics of vitrectomy probes.

PURPOSE: To characterize the fluidics of vitreous cutter port in response to aspiration and blade motion using particle image velocimetry techniques. Diverse surgical scenarios and fluid characteristics were replicated.
METHODS: The 23-gauge vitreous cutters were immersed in seeded Balanced Salt Solution (BSS) (Alcon, Forth Worth, TX) or egg albumen, and high-speed video was recorded. Fluid velocity, kinetic energy (KE), and acceleration generated by Venturi and peristaltic pumps were measured in aspiration only (200 and 300 mmHg), low-speed vitrectomy (1,600 cuts per minute; 200 mmHg vacuum), and high-speed vitrectomy (3,000 cuts per minute; 300 mmHg vacuum) modes.
RESULTS: The Venturi pump generated significantly higher KE than peristaltic pump in BSS (P < 0.0001 for each pair), and aspiration only yielded significantly higher KE. Cutting activation generated significant acceleration (P < 0.001), and the peristaltic pump produced higher positive and negative acceleration peaks (P < 0.001) than the Venturi pump. In egg albumen, the peristaltic pump generated significantly more KE than the Venturi pump (P < 0.001) and perturbed a much wider area. Acceleration was higher for the peristaltic pump in low-speed mode (P < 0.001), whereas in high-speed modality, the Venturi pump produced the highest acceleration peaks (P < 0.001).
CONCLUSION: Pump type and blade motion largely influence velocity, KE, and acceleration. In BSS, the Venturi pump induces higher KE and acceleration, although perturbing fluid less diffusely. In egg albumen, the peristaltic pump perturbed a much wider area and induced a higher KE and acceleration than the Venturi pump, even more so at lower cut rates. As a conclusion, particle image velocimetry allowed precise characterization of fluid velocity in response to cutter activation, suggesting a pragmatic approach to surgical scenarios.