title: Mathematical Modeling of Outflow Facility Increase With Trabecular Meshwork Bypass and Schlemm Canal Dilation.
abstract: OBJECTIVE
  To mathematically model the conventional aqueous humor outflow system with trabecular meshwork (TM) bypass and Schlemm canal (SC) dilation.
  
  
  METHODS
  The SC was modeled as a rectangular channel with the TM modeled as a permeable membrane. The collector channels (CCs) were modeled as fluid sinks distributed along the outer wall of SC. Two different implants were investigated in this study. The Hydrus Microstent (scaffold) was modeled with a TM bypass and a dilated region in SC that was 7 or 15 mm long and approximately 5-fold larger than the normal height of SC (h0). The iStent trabecular microbypass was modeled with a similar structure except that the dilated region in SC was 1 mm long and 25% larger than h0.
  
  
  RESULTS
  Creation of a TM bypass structure would increase the pressure in the surrounding regions inside the SC and make it close to the intraocular pressure. SC dilation would increase the pressure more uniformly in the dilated region. The pressure increase led to higher flow rates in SC and CCs, and subsequently increased outflow facility (C). If CCs were uniformly distributed, the increase in C was the smallest after implantation of 1 microbypass, compared with that after implantation of 2 microbypasses or 1 scaffold. If CCs were nonuniformly distributed, the magnitude of increase in C was sensitive to the location of implant, and the sensitivity was higher for the microbypass than the scaffold.
  
  
  CONCLUSIONS
  The study showed that creation of TM bypass and SC dilation significantly increased outflow facility, and the amount of increase correlated with the length of dilated regions in SC.
authors.affiliation: Departments of *Biomedical Engineering †Ophthalmology, Duke University, Durham, NC ‡Ivantis Inc., Irvine, CA §Department of Ophthalmology, Maisonneuve-Rosemont Hospital, Montreal, QC, Canada.
authors.forename: Fan
authors.initials: F
authors.lastname: Yuan
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Schieber
authors.forename: Lucinda J
authors.initials: LJ
authors.lastname: Camras
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Harasymowycz
authors.forename: Leon W
authors.initials: LW
authors.lastname: Herndon
authors.forename: R Rand
authors.initials: RR
authors.lastname: Allingham
mesh_terms: D001082:Aqueous Humor / Q000378:metabolism*; D004108:Dilatation, Pathologic; D020327:Glaucoma Drainage Implants; D006801:Humans; D007429:Intraocular Pressure; D016850:Limbus Corneae / Q000378:metabolism / Q000473:pathology*; D008962:Models, Theoretical; D014065:Tonometry, Ocular; D014129:Trabecular Meshwork / Q000378:metabolism*