title: Vitreous flow rates through dual pneumatic cutters: effects of duty cycle and cut rate.
abstract: OBJECTIVE
  We aimed to investigate effects of instrument settings on porcine vitreous flow rates through dual pneumatic high-speed vitrectomy probes.
  
  
  METHODS
  The CONSTELLATION(®) Vision System was tested with 250, 450, and 650 mmHg of vacuum using six ULTRAVIT(®) vitrectomy probes of each diameter (25+(®), 25, 23, and 20 gauge) operated from 500 cuts per minute (cpm) up to 5,000 cpm. Duty cycle modes tested included biased open, 50/50, and biased closed. Flow rates were calculated by assessing the change in weight of porcine eyes during vitreous aspiration. Volumetric flow rate was measured with a computer-connected electronic scale.
  
  
  RESULTS
  At lower cut rates, the biased open mode produced higher flow than did the 50/50 mode, which produced higher flow than did the biased closed mode. In the biased closed and 50/50 modes, vitreous flow rates tended to increase with increasing cut rate. Vitreous flow rates in the biased open duty cycle mode remained relatively constant across cut rates.
  
  
  CONCLUSIONS
  Vitreous flow rates through dual pneumatic vitrectomy probes could be manipulated by changing the duty cycle modes on the vitrectomy system. Differences in duty cycle behavior suggest that high-speed cut rates of 5,000 cpm may optimize vitreous aspiration.
authors.affiliation: Medical Affairs, Alcon Research, Ltd, Lake Forest, CA, USA.
authors.forename: Dina Joy K
authors.initials: DJ
authors.lastname: Abulon
keywords: 20-gauge vitrectomy; 23-gauge vitrectomy; 25-gauge vitrectomy; Constellation Vision System; aspiration; enhanced 25-gauge vitrectomy