title: Precise montaging and metric quantification of retinal surface area from ultra-widefield fundus photography and fluorescein angiography.
abstract: OBJECTIVE
  Accurate quantification of retinal surface area from ultra-widefield (UWF) images is challenging due to warping produced when the retina is projected onto a two-dimensional plane for analysis. By accounting for this, the authors sought to precisely montage and accurately quantify retinal surface area in square millimeters.
  
  
  METHODS
  Montages were created using Optos 200Tx (Optos, Dunfermline, U.K.) images taken at different gaze angles. A transformation projected the images to their correct location on a three-dimensional model. Area was quantified with spherical trigonometry. Warping, precision, and accuracy were assessed.
  
  
  RESULTS
  Uncorrected, posterior pixels represented up to 79% greater surface area than peripheral pixels. Assessing precision, a standard region was quantified across 10 montages of the same eye (RSD: 0.7%; mean: 408.97 mm(2); range: 405.34-413.87 mm(2)). Assessing accuracy, 50 patients' disc areas were quantified (mean: 2.21 mm(2); SE: 0.06 mm(2)), and the results fell within the normative range.
  
  
  CONCLUSIONS
  By accounting for warping inherent in UWF images, precise montaging and accurate quantification of retinal surface area in square millimeters were achieved.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Croft
authors.forename: Jano
authors.initials: J
authors.lastname: van Hemert
authors.forename: Charles C
authors.initials: CC
authors.lastname: Wykoff
authors.forename: David
authors.initials: D
authors.lastname: Clifton
authors.forename: Michael
authors.initials: M
authors.lastname: Verhoek
authors.forename: Alan
authors.initials: A
authors.lastname: Fleming
authors.forename: David M
authors.initials: DM
authors.lastname: Brown
mesh_terms: D005451:Fluorescein Angiography / Q000379:methods*; D005654:Fundus Oculi; D006801:Humans; D008962:Models, Theoretical; D015588:Observer Variation; D010781:Photography / Q000379:methods*; D015203:Reproducibility of Results; D012164:Retinal Diseases / Q000175:diagnosis*; D012171:Retinal Vessels / Q000473:pathology