title: Intraocular pressure, blood pressure, and retinal blood flow autoregulation: a mathematical model to clarify their relationship and clinical relevance.
abstract: OBJECTIVE
  This study investigates the relationship between intraocular pressure (IOP) and retinal hemodynamics and predicts how arterial blood pressure (BP) and blood flow autoregulation (AR) influence this relationship.
  
  
  METHODS
  A mathematical model is developed to simulate blood flow in the central retinal vessels and retinal microvasculature as current flowing through a network of resistances and capacitances. Variable resistances describe active and passive diameter changes due to AR and IOP. The model is validated by using clinically measured values of retinal blood flow and velocity. The model simulations for six theoretical patients with high, normal, and low BP (HBP-, NBP-, LBP-) and functional or absent AR (-wAR, -woAR) are compared with clinical data.
  
  
  RESULTS
  The model predicts that NBPwAR and HBPwAR patients can regulate retinal blood flow (RBF) as IOP varies between 15 and 23 mm Hg and between 23 and 29 mm Hg, respectively, whereas LBPwAR patients do not adequately regulate blood flow if IOP is 15 mm Hg or higher. Hemodynamic alterations would be noticeable only if IOP changes occur outside of the regulating range, which, most importantly, depend on BP. The model predictions are consistent with clinical data for IOP reduction via surgery and medications and for cases of induced IOP elevation.
  
  
  CONCLUSIONS
  The theoretical model results suggest that the ability of IOP to induce noticeable changes in retinal hemodynamics depends on the levels of BP and AR of the individual. These predictions might help to explain the inconsistencies found in the clinical literature concerning the relationship between IOP and retinal hemodynamics.
authors.affiliation: Department of Mathematical Sciences, Indiana University Purdue University Indianapolis, Indianapolis, Indiana, United States Eugene and Marilyn Glick Eye Institute and Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Guidoboni
authors.affiliation: Eugene and Marilyn Glick Eye Institute and Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States.
authors.forename: Alon
authors.initials: A
authors.lastname: Harris
authors.affiliation: Department of Mathematical Sciences, Indiana University Purdue University Indianapolis, Indianapolis, Indiana, United States.
authors.forename: Simone
authors.initials: S
authors.lastname: Cassani
authors.affiliation: Department of Mathematical Sciences, Indiana University Purdue University Indianapolis, Indianapolis, Indiana, United States.
authors.forename: Julia
authors.initials: J
authors.lastname: Arciero
authors.affiliation: Eugene and Marilyn Glick Eye Institute and Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States.
authors.forename: Brent
authors.initials: B
authors.lastname: Siesky
authors.affiliation: Eugene and Marilyn Glick Eye Institute and Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States.
authors.forename: Annahita
authors.initials: A
authors.lastname: Amireskandari
authors.affiliation: Eugene and Marilyn Glick Eye Institute and Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States.
authors.forename: Leslie
authors.initials: L
authors.lastname: Tobe
authors.affiliation: Eugene and Marilyn Glick Eye Institute and Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States.
authors.forename: Patrick
authors.initials: P
authors.lastname: Egan
authors.affiliation: Eye Clinic, Lithuanian University of Health Sciences, Kaunas, Lithuania.
authors.forename: Ingrida
authors.initials: I
authors.lastname: Januleviciene
authors.affiliation: Eugene and Marilyn Glick Eye Institute and Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, Indiana, United States.
authors.forename: Joshua
authors.initials: J
authors.lastname: Park
mesh_terms: D001794:Blood Pressure; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D017078:Laser-Doppler Flowmetry; D008962:Models, Theoretical; D009798:Ocular Hypertension / Q000503:physiopathology*; D009898:Optic Disk / Q000098:blood supply / Q000503:physiopathology; D012039:Regional Blood Flow / Q000502:physiology*; D012160:Retina / Q000503:physiopathology; D012171:Retinal Vessels / Q000503:physiopathology*; D014655:Vascular Resistance
keywords: autoregulation; blood flow; intraocular pressure; mathematical model; retina