title: Hydraulic Resistance of Vitreous Cutters: The Impact of Blade Design and Cut Rate.
abstract: OBJECTIVE
  To measure the hydraulic resistance (HR) of vitreous cutters equipped with a Regular guillotine Blade (RB) or double edge blade (DEB) at cut rates comprised between 0 and 12,000 cuts per minute (CPM) and compare it with vitreous fragment size. This was an in vitro experimental study; in vivo HR measure and vitreous sampling.
  
  
  METHODS
  HR, defined as aspiration pressure/flow rate, was measured in balanced salt solution (BSS; Alcon, Fort Worth, TX) (in vitro) and during pars plana vitrectomy of 20 consecutive patients aged 18 to 65, undergoing macular surgery. HR was recorded at increasing cut rates (500-6000 CPM for the RB and 500-12,000 CPM for the DEB; 5 mL/min flow). Vitreous samples were withdrawn and analyzed with Western and collagen type II and IX immunostaining to evaluate protein size. The main outcome measures were hydraulic resistance (mm Hg/ml/min [±SD]) and optic density for Western blot and immunostaining.
  
  
  RESULTS
  RB and DEB showed identical HR in BSS between 0 and 3000 CPM. Above 3000 CPM, RB HR steadily increased, and was significantly higher than DEB HR. Vitreous HR was also similar for the two blades between 0 and 1500 CPM. Above 1500 CPM, RB offered a significantly higher resistance. Western blot and immunostaining of vitreous samples did not yield a significant difference in size, regardless of blade type and cut rate.
  
  
  CONCLUSIONS
  DEB is more efficient, offering a lower HR than RB over 1500 CPM in human vitreous. There is no viscosity reduction as a function of cut-rate between 1500 and 12,000 CPM, as HR does not vary.
  
  
  CONCLUSIONS
  Future vitreous cutters will benefit of a DEB; optimal cut rate needs to be defined, and the simple increase of cut rate does not provide benefits after a certain limit to be assessed.
authors.affiliation: IRCCS Azienda Ospedaliera Universitaria San Martino, IST Istituto Nazionale per la Ricerca sul Cancro, Genoa, 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: Carlo
authors.initials: C
authors.lastname: Malvasi
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: Mario
authors.initials: M
authors.lastname: Morini
authors.affiliation: IRCCS - G.B. Bietti Foundation, Rome, Italy.
authors.forename: Graziana
authors.initials: G
authors.lastname: Esposito
authors.affiliation: IRCCS - G.B. Bietti Foundation, Rome, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Micera
authors.affiliation: University of Rome La Sapienza, Rome, Italy.
authors.forename: Natale Mario
authors.initials: NM
authors.lastname: di Luca
authors.affiliation: IRCCS - G.B. Bietti Foundation, Rome, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Ripandelli
keywords: cut rate; human vitreous hydraulic resistance; pars plana vitrectomy; vitreous cutter; vitreous viscosity; volumetric flow rate