title: Regionally Discrete Aqueous Humor Outflow Quantification Using Fluorescein Canalograms.
abstract: OBJECTIVE
  To visualize and quantify conventional outflow directly in its anatomic location.
  
  
  METHODS
  We obtained fluorescein canalograms in six porcine whole eyes and six porcine anterior segment cultures. Eyes were perfused with a constant pressure of 15 mmHg using media containing 0.017 mg/ml fluorescein. Flow patterns were visualized using a stereo dissecting microscope equipped for fluorescent imaging. Images were captured every 30 seconds for 20 minutes for time lapse analysis. Anterior chamber cultures were imaged again on day three of culture. Canalograms were first analyzed for filling time per quadrant. We then wrote a program to automatically compute focal flow fits for each macropixel and to detect convergent perilimbal flow patterns with macropixels grouped into 3 equal-radial width rings around the cornea. A generalized additive model was used to determine fluorescence changes of individual macropixels.
  
  
  RESULTS
  The resulting imaging algorithm deployed 1024 macropixels that were fit to determine maximum intensity and time to fill. These individual fits highlighted the focal flow function. In whole eyes, significantly faster flow was seen in the inferonasal (IN) and superonasal (SN) quadrants compared to the superotemporal (ST) and inferotemporal (IT) ones (p<0.05). In anterior chamber cultures, reduced flow on day 1 increased in all quadrants on day 3 except in IT (p<0.05). Perilimbal ring analysis uncovered convergent perilimbal flow.
  
  
  CONCLUSIONS
  An algorithm was developed that analyzes regional and circumferential outflow patterns. This algorithm found flow patterns that changed over time and differ in whole eyes and anterior segment cultures.
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, United States of America.|The Louis J. Fox Center for Vision Restoration, School of Medicine, University of Pittsburgh, Pittsburgh, United States of America.
authors.forename: Ralitsa T
authors.initials: RT
authors.lastname: Loewen
authors.affiliation: Department of Ophthalmology, School of Medicine, Vanderbilt University, Nashville, United States of America.
authors.forename: Eric N
authors.initials: EN
authors.lastname: Brown
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, United States of America.|The Louis J. Fox Center for Vision Restoration, School of Medicine, University of Pittsburgh, Pittsburgh, United States of America.
authors.forename: Pritha
authors.initials: P
authors.lastname: Roy
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, United States of America.|The Louis J. Fox Center for Vision Restoration, School of Medicine, University of Pittsburgh, Pittsburgh, United States of America.
authors.forename: Joel S
authors.initials: JS
authors.lastname: Schuman
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, United States of America.|The Louis J. Fox Center for Vision Restoration, School of Medicine, University of Pittsburgh, Pittsburgh, United States of America.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Sigal
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, United States of America.|The Louis J. Fox Center for Vision Restoration, School of Medicine, University of Pittsburgh, Pittsburgh, United States of America.
authors.forename: Nils A
authors.initials: NA
authors.lastname: Loewen
mesh_terms: D000818:Animals; D000867:Anterior Chamber / Q000378:metabolism; D001082:Aqueous Humor / Q000378:metabolism*; D019793:Fluorescein / Q000378:metabolism*; D021621:Imaging, Three-Dimensional; D009885:Ophthalmology / Q000295:instrumentation*; D034421:Sus scrofa; D059008:Time-Lapse Imaging
chemical_list: D019793:Fluorescein