title: Semiautomated image processing method for identification and quantification of geographic atrophy in age-related macular degeneration.
abstract: OBJECTIVE
  To determine intraobserver and interobserver longitudinal measurement variability of novel semiautomated software for quantification of age-related macular degeneration-associated geographic atrophy (GA) based on confocal scanning laser ophthalmoscopy fundus autofluorescence (FAF) imaging.
  
  
  METHODS
  Three-field FAF (excitation 488 nm, emission 500-700 nm), near-infrared reflectance (820 nm), and blue reflectance (488 nm) images of 30 GA subjects were recorded according to a standardized protocol at baseline after 6 and 12 months. At all visits, the GA area was analyzed on central FAF images by seven independent readers using semiautomated software. The software allows direct export of FAF images from the database and semiautomated detection of atrophic areas by shadow correction, vessel detection, and selection of seed points.
  
  
  RESULTS
  The mean size of atrophy at baseline and the mean progression rate were 5.96 mm² (range, 1.80-15.87) and 1.25 mm²/year (0.42-2.93), respectively. Mean difference of interobserver agreement (Bland-Altman statistics) ranged from -0.25 to 0.30 mm² for the baseline visit and from -0.14 to 0.11 mm²/year for the atrophy progression rate. Corresponding reflectance images were helpful for lesion boundary discrimination, particularly for evaluation of foveal GA involvement and when image quality was poor.
  
  
  CONCLUSIONS
  The new image processing software offers an accurate, reproducible, and time-efficient identification and quantification of outer retinal atrophy and its progression over time. It facilitates measurements both in natural history studies and in interventional trials to evaluate new pharmacologic agents designed to limit GA enlargement.
authors.affiliation: Department of Ophthalmology and GRADE Reading Center, University of Bonn, Bonn, Germany. steffen.schmitz-valckenberg@ukb.uni-bonn.de
authors.forename: Steffen
authors.initials: S
authors.lastname: Schmitz-Valckenberg
authors.forename: Christian K
authors.initials: CK
authors.lastname: Brinkmann
authors.forename: Florian
authors.initials: F
authors.lastname: Alten
authors.forename: Philipp
authors.initials: P
authors.lastname: Herrmann
authors.forename: Nina K
authors.initials: NK
authors.lastname: Stratmann
authors.forename: Arno P
authors.initials: AP
authors.lastname: Göbel
authors.forename: Monika
authors.initials: M
authors.lastname: Fleckenstein
authors.forename: Martin
authors.initials: M
authors.lastname: Diller
authors.forename: Glenn J
authors.initials: GJ
authors.lastname: Jaffe
authors.forename: Frank G
authors.initials: FG
authors.lastname: Holz
mesh_terms: D018450:Disease Progression; D005451:Fluorescein Angiography; D057092:Geographic Atrophy / Q000175:diagnosis*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008268:Macular Degeneration / Q000175:diagnosis*; D008875:Middle Aged; D015588:Observer Variation; D009887:Ophthalmoscopy; D015203:Reproducibility of Results