title: Fluid Dynamics of a Novel Micro-Fistula Implant for the Surgical Treatment of Glaucoma.
abstract: OBJECTIVE
  The purpose of this study was to describe the fluidics of a novel non-valved glaucoma implant designed to prevent hypotony and compare the fluidics of this device with two commonly used non-valved glaucoma devices.
  
  
  METHODS
  The XEN 45 micro-fistula implant was designed to limit hypotony by virtue of its length and width according to the Hagen-Poiseuille equation. Flow testing was performed using a syringe pump and pressure transducer at multiple flow rates. The pressure differentials across the XEN implant, the Ex-Press implant, and 10 mm of silicone tubing from a Baerveldt implant at a physiologic flow rate (2.5 μL/min) were extrapolated.
  
  
  RESULTS
  The XEN 45 achieved a steady-state pressure calculated at 7.56 mm Hg at 2.5 μL/min. At the same flow rate, the Ex-Press device and Baerveldt tubing reached steady-state pressures of 0.09 and 0.01 mm Hg, respectively.
  
  
  CONCLUSIONS
  Under flow testing, the XEN micro-fistula implant was able to maintain backpressure above numerical hypotony levels without the use of complex valve systems. This is due to the XEN implant's design, derived from the principles that dictate Newtonian fluids.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, United States.
authors.forename: Arsham
authors.initials: A
authors.lastname: Sheybani
authors.affiliation: Department of Ophthalmology, University Clinic Salzburg/SALK, Austria 3Paracelsus Medical University, Salzburg, Austria.
authors.forename: Herbert
authors.initials: H
authors.lastname: Reitsamer
authors.affiliation: Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada 5Credit Valley Eye Care, Mississauga, Ontario, Canada 6Trillium Health Partners, Mississauga, Ontario, Canada.
authors.forename: Iqbal Ike K
authors.initials: II
authors.lastname: Ahmed
mesh_terms: D000818:Animals; D001082:Aqueous Humor / Q000502:physiology*; D005901:Glaucoma / Q000503:physiopathology / Q000601:surgery*; D020327:Glaucoma Drainage Implants; D006801:Humans; D057446:Hydrodynamics; D007429:Intraocular Pressure; D008904:Miniaturization; D011474:Prosthesis Design; D013552:Swine