title: Feasibility of conjunctival hemodynamic measurements in rabbits: reproducibility, validity, and response to acute hypotension.
abstract: OBJECTIVE
  To evaluate the feasibility of conjunctival hemodynamic measurements based on assessment of reproducibility, validity, and response to acute hypotension.
  
  
  METHODS
  Image sequences of the conjunctival microvasculature of rabbits were captured using a slit lamp biomicroscope under a steady-state condition, after topical administration of phenylephrine, and after intravenous administration of esmolol. Venous hemodynamic parameters (diameter, blood velocity, blood flow, and wall shear stress) were derived.
  
  
  RESULTS
  Conjunctival venous diameters ranged from 9 to 34 μm and blood velocities ranged from 0.08 to 0.95 mm/s. Coefficients of variation of venous diameter and blood velocity measurements were, on average, 6% and 14%, respectively. Automated and manual measurements of venous diameter and velocity were highly correlated (R = 0.97; p < 0.001; n = 16). With phenylephrine administration, diameter and velocity were reduced by 21% and 69%, respectively. Following esmolol administration, blood pressure was reduced with a concomitant decrease in velocity, followed by recovery to baseline. Venous blood velocity, flow, and WSS were correlated with blood pressure (R ≥ 0.52; p ≤ 0.01).
  
  
  CONCLUSIONS
  The feasibility of quantifying alterations in microvascular hemodynamics in the bulbar conjunctiva was established. The method is of potential value in evaluating microcirculatory hemodynamics related to cardiovascular function.
authors.affiliation: Department of Ophthalmology, Loyola University Medical Center, Maywood, Illinois, USA.
authors.forename: Bruce
authors.initials: B
authors.lastname: Gaynes
authors.forename: Pang-Yu
authors.initials: PY
authors.lastname: Teng
authors.forename: Justin
authors.initials: J
authors.lastname: Wanek
authors.forename: Mahnaz
authors.initials: M
authors.lastname: Shahidi
mesh_terms: D000208:Acute Disease; D058671:Adrenergic beta-1 Receptor Antagonists / Q000009:adverse effects; D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D003228:Conjunctiva / Q000098:blood supply* / Q000503:physiopathology*; D007022:Hypotension / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D010656:Phenylephrine / Q000009:adverse effects / Q000494:pharmacology; D011412:Propanolamines / Q000009:adverse effects / Q000494:pharmacology; D011817:Rabbits; D015203:Reproducibility of Results; D014680:Veins / Q000473:pathology / Q000503:physiopathology
chemical_list: D058671:Adrenergic beta-1 Receptor Antagonists; D011412:Propanolamines; D010656:Phenylephrine; C036604:esmolol