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Guillotine performance: duty cycle analysis of vitrectomy systems.

PURPOSE
To evaluate the duty cycle of different vitrectomy cutters and classify their blade movement.


METHODS
A precise weighing (0.01 g) high speed (2 samples/s) balance was used to study the 20-gauge and 25-gauge Bausch & Lomb Lightning-Millenium (St. Louis, MO), the 20-gauge (1500 cpm) and the 25-gauge Alcon Accurus (Fort Worth, TX), the 20-gauge Alcon Innovit, and the 23-gauge DORC (Netherlands) cutters. The weight of balanced saline solution (BSS) was recorded in real time using LabView software and then translated into a graph of volume removed versus time. Variable cut rates and vacuum pressures were analyzed in vitreous and BSS. A high-speed (400 frames/s) camera was used to record cutting for each condition.


RESULTS
Three types of duty cycle were investigated: parabolic incomplete (pneumatic), sinusoid (electric), and trapezoid (double pneumatic). The parabolic incomplete and trapezoid had a decreased duty cycle at 1500 cuts per minute when it was compared to 600 cuts per minute. The sinusoid had no statistical difference between cut rates.


CONCLUSIONS
Systems showed different performances of duty cycle. This new classification will be useful for improved understanding of vitrectomy in these different systems.