title: Automated analysis of digital fundus autofluorescence images of geographic atrophy in advanced age-related macular degeneration using confocal scanning laser ophthalmoscopy (cSLO).
abstract: BACKGROUND
  Fundus autofluorescence (AF) imaging using confocal scanning laser ophthalmoscopy (cSLO) provides an accurate delineation of areas of geographic atrophy (GA). Automated computer-assisted methods for detecting and removing interfering vessels are needed to support the GA quantification process in longitudinal studies and in reading centres.
  
  
  METHODS
  A test tool was implemented that uses region-growing techniques to segment GA areas. An algorithm for illuminating shadows can be used to process low-quality images. Agreement between observers and between three different methods was evaluated by two independent readers in a pilot study. Agreement and objectivity were assessed using the Bland-Altman approach.
  
  
  RESULTS
  The new method (C) identifies vascular structures that interfere with the delineation of GA. Results are comparable to those of two commonly used procedures (A, B), with a mean difference between C and A of -0.67 mm2 (95% CI [-0.99, -0.36]), between B and A of -0.81 mm2, (95% CI [-1.08, -0.53]), and between C and B of 0.15 mm2 (95% CI [-0.12, 0.41]). Objectivity of a method is quantified by the mean difference between observers: A 0.30 mm2 (95% CI [0.02, 0.57]), B -0.11 mm2 (95% CI [-0.28, 0.10]), and C 0.12 mm2 (95% CI [0.02, 0.22]).
  
  
  CONCLUSIONS
  The novel procedure is comparable with regard to objectivity and inter-reader agreement to established methods of quantifying GA. It considerably speeds up the lengthy measurement process in AF with well defined GA zones.
authors.affiliation: Institute of Medical Biometry and Informatics, University of Heidelberg, Im Neuenheimer Feld 305, 69120 Heidelberg, Germany. deckert@imbi.uni-heidelberg.de
authors.forename: A
authors.initials: A
authors.lastname: Deckert
authors.forename: S
authors.initials: S
authors.lastname: Schmitz-Valckenberg
authors.forename: J
authors.initials: J
authors.lastname: Jorzik
authors.forename: A
authors.initials: A
authors.lastname: Bindewald
authors.forename: F G
authors.initials: FG
authors.lastname: Holz
authors.forename: U
authors.initials: U
authors.lastname: Mansmann
mesh_terms: D000465:Algorithms; D001284:Atrophy; D005453:Fluorescence; D005654:Fundus Oculi; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007834:Lasers; D008268:Macular Degeneration / Q000175:diagnosis*; D015588:Observer Variation; D009887:Ophthalmoscopy / Q000379:methods*; D010857:Pigment Epithelium of Eye / Q000098:blood supply / Q000473:pathology*; D010865:Pilot Projects; D015203:Reproducibility of Results