title: Instantaneous flow rate of vitreous cutter probes.
abstract: OBJECTIVE
  We report on instantaneous volumetric flow rate of vitreous cutters measured by means of particle image velocimetry (PIV).
  
  
  METHODS
  In an in vitro experimental study, vitreous cutters mounting a regular blade (RB) or modified Twedge blade (TB) engineered for higher flow were connected to a console machine equipped with a double peristaltic and Venturi pump, and immersed in balanced salt solution (BSS). Instantaneous flow was measured on aspiration tubing sections proximal to the cutter hand piece. Measures settings were as follows: (1) regular functioning at 3000 and 6000 cuts per minute (cpm) with 300 mm Hg aspiration with both pumps, (2) aspiration tubing clamped proximal to pump cassette, and (3) aspiration tubing clamped proximal to hand piece, and (4) flow fluctuation as a function of cut rate also was calculated. For main outcome measures, instantaneous volumetric flow rate in mL/min and flow fluctuation measured as the standard deviation of flow rate were measured.
  
  
  RESULTS
  Regular functioning shows sinusoidal flow oscillating at cut rate frequency, with amplitude between ±50 mL/min at 3000 cpm and ±35 mL/min at 6000 cpm. The TB always determined a bimodal wave and neither blade nor pump type influenced the sinusoidal pattern of flow. Clamping aspiration tubing zeroes flow, but does not influence fluctuation frequency or amplitude. Clamping at the hand piece determined a significantly higher oscillation. Oscillation amplitude retain a typical resonance pattern with significant changes in function of cut rate and resonance occurs at approximately 4000 cpm.
  
  
  CONCLUSIONS
  Cutter blade action determines instantaneous flow rate fluctuation that interferes significantly with cutter suction and hampers a steady suction through cutter port. In a surgical scenario, this translates into a higher risk of inadvertent retinal entrapment and lower predictability of cutter behavior, especially at frequency approaching resonance.
authors.affiliation: Eye Hospital of Rome, Rome, Italy.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Rossi
authors.affiliation: University of Cagliari, DICAAR, Cagliari, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Querzoli
authors.affiliation: Optikon 2000, Inc., Rome, Italy.
authors.forename: Giampiero
authors.initials: G
authors.lastname: Angelini
authors.affiliation: Optikon 2000, Inc., Rome, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Rossi
authors.affiliation: Optikon 2000, Inc., Rome, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Malvasi
authors.affiliation: Eye Hospital of Rome, Rome, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Iossa
authors.affiliation: Fondazione G.B. Bietti IRCCS, Rome, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Ripandelli
mesh_terms: D057446:Hydrodynamics; D008866:Microsurgery / Q000295:instrumentation*; D014741:Video Recording; D014821:Vitrectomy / Q000295:instrumentation* / Q000379:methods; D014822:Vitreous Body / Q000601:surgery*
keywords: flow rate; fluid dynamics; pars plana vitrectomy; retinal detachment; vitrectomy; vitreous cutter