title: Port geometry and its influence on vitrectomy.
abstract: OBJECTIVE
  To determine the influence of port geometry on water and vitreous flow rates and test novel vitreous cutter tips in specific surgical situations.
  
  
  METHODS
  Custom 20-gauge and 25-gauge vitreous cutter tips with different sized ports were evaluated through porcine vitreous and water flow rates. Five cutter tips were designed and fabricated for specific surgical functionalities. Tips were compared with a normal control tip and evaluated by water and porcine vitreous flow rates, vacuum level required to cut porcine retina, time required to cut and aspirate a porcine lens, and surgical evaluation in enucleated porcine eyes.
  
  
  RESULTS
  Both vitreous and water flow asymptotically approached a maximum flow as the port diameter increased. Some tips removed water faster than the normal control tip, but none removed vitreous or lens faster. Several tips required higher vacuum levels to cut retina than the normal tip.
  
  
  CONCLUSIONS
  Increasing the port diameter of a vitreous cutter to increase flow becomes less effective as the port becomes larger. Furthermore, modifying the port geometry of a vitreous cutter affects its surgical interactions with tissue. In the future, combinational instruments or surgery specific instruments may allow the surgeon to use an optimal port for a specific surgical task.
authors.affiliation: Department of Ophthalmology, Keck School of Medicine, University of Southern California, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: DeBoer
authors.forename: Sophia
authors.initials: S
authors.lastname: Fang
authors.forename: Luiz H
authors.initials: LH
authors.lastname: Lima
authors.forename: Matt
authors.initials: M
authors.lastname: McCormick
authors.forename: Prashant
authors.initials: P
authors.lastname: Bhadri
authors.forename: Ralph
authors.initials: R
authors.lastname: Kerns
authors.forename: Mark
authors.initials: M
authors.lastname: Humayun
mesh_terms: D000818:Animals; D004867:Equipment Design; D066298:In Vitro Techniques; D007908:Lens, Crystalline / Q000601:surgery; D012160:Retina / Q000601:surgery; D013552:Swine; D013997:Time Factors; D014821:Vitrectomy / Q000295:instrumentation*; D014822:Vitreous Body / Q000503:physiopathology; D014867:Water
chemical_list: D014867:Water