PURPOSE: To evaluate vitreous flow rates of 25-Gauge (Ga) dual-action, 25,000 cuts per minute (cpm) vitrectomy probes at various vacuum settings and to provide recommendations on optimized vacuum settings for retina shaving.

METHODS: The Bausch + Lomb Bi-Blade+ (BB+) 25,000 cpm dual-action pneumatic cutter was compared to the Bi-Blade (BB) 15,000 cpm cutter. Vitreous flow rates were measured in pig eyes with an open-sky technique with 50 to 660 mmHg vacuum at their maximum cut rates. The eyes were weighed before and after each timed test to calculate flow rate. To analyze near-port flow behavior, particle imaging velocimetry (PIV) was conducted in water at atmospheric pressure with vacuums ranging from 0 to 50 mmHg. Flow dynamics were visualized using Kenalog markers and captured at 10,000 frames per second.

RESULTS: Vitreous flow increased with vacuum for both the BB and BB+ cutters. At 50 mmHg, the BB achieved flow rates of 0.2±0.05 g/min, compared to the BB+ at 0.3±0.02 g/min. At 660 mmHg, flow rates were 3.63±0.07 g/min for the BB and 4.35±0.05 g/min for the BB+, representing a 20% improvement at maximum vacuum. Across the entire vacuum range, the BB+ demonstrated an average flow rate increase of 25% over the BB. The BB+ achieved equivalent flow to the BB at 660 mmHg when operated at only 520 mmHg, reducing the required vacuum by 120 mmHg. PIV of the BB+ port showed localized flow dynamics near the port. At 0 mmHg vacuum, localized outward flow was observed due to blade motion, with velocities reaching 0.16 m/s. At 50 mmHg, no residual outflow was detected.

CONCLUSIONS: The 25 Ga, dual-action 25,000 cpm probes demonstrate superior vitreous aspiration efficiency compared to the 15,000 cpm probes, achieving comparable flow rates with lower vacuum settings. Dual action cutters can support stable retina shaving at low vacuums.