title: Vitreous dynamics: vitreous flow analysis in 20-, 23-, and 25-gauge cutters.
abstract: OBJECTIVE
  To evaluate porcine vitreous flow and balanced saline solution (BSS) flow rates in different vitrectomy systems.
  
  
  METHODS
  Porcine vitreous was obtained within 24 hours of slaughter. A high-speed (2 samples/s) balance, precise to 0.01 g, was used. Variable cut rates and vacuum pressures were analyzed in vitreous and BSS. The vitreous was labeled with glass microspheres and triamcinolone acetonide. A high-speed (400 frames/s) camera was used to record cutting for each condition.
  
  
  RESULTS
  For all cutters, there was no vitreous flow at zero cut rates (off). In 25-gauge cutters, at 500 mmHg of vacuum, the electric cutter produced higher average flow rates at high cut rates (600 cpm, 0.004 mL/s, and 1500 cpm, 0.013 mL/s) than pneumatic, which demonstrated a decreased flow at speeds higher than 1000 cpm (1000 cpm, 0.015 mL/s, and 1500 cpm, 0.006 mL/s). The percentage of vitreous flow rate/BSS flow rate in different aspiration and cut rates showed an ascending curve. This demonstrates evidence of flow obstruction in 25- (all cut rates), 23- (all cut rates), and 20-gauge (all cut rates). Flow obstruction and surge movements were seen in the high-speed videos.
  
  
  CONCLUSIONS
  The vitrectomy systems each illustrate different performances of vitreous removal. The physical characteristics of vitreous resulted in nonuniform flow in all vitreous cutters.
authors.affiliation: Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA. octavianomj@terra.com.br
authors.forename: Octaviano
authors.initials: O
authors.lastname: Magalhaes
authors.forename: Lawrence
authors.initials: L
authors.lastname: Chong
authors.forename: Charles
authors.initials: C
authors.lastname: DeBoer
authors.forename: Prashant
authors.initials: P
authors.lastname: Bhadri
authors.forename: Ralph
authors.initials: R
authors.lastname: Kerns
authors.forename: Aaron
authors.initials: A
authors.lastname: Barnes
authors.forename: Sophia
authors.initials: S
authors.lastname: Fang
authors.forename: Mark
authors.initials: M
authors.lastname: Humayun
mesh_terms: D000085:Acetates / Q000378:metabolism; D000818:Animals; D004338:Drug Combinations; D008903:Minerals / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism; D013552:Swine; D014821:Vitrectomy / Q000295:instrumentation*; D014822:Vitreous Body / Q000378:metabolism*
chemical_list: D000085:Acetates; C030660:BSS solution; D004338:Drug Combinations; D008903:Minerals; D012965:Sodium Chloride