title: Automated assessment of the optic nerve head on stereo disc photographs.
abstract: OBJECTIVE
  To develop automated software for optic nerve head (ONH) quantitative assessment from stereoscopic disc photographs and to evaluate its performance in comparison with human expert assessment.
  
  
  METHODS
  A fully automated system, including three-dimensional ONH modeling, disc margin detection, cup margin detection, and calculation of stereometric ONH parameters, was developed and tested. One eye each from 54 subjects (23 healthy, 17 suspected glaucoma, and 14 glaucoma) was enrolled. The majority opinion of three experts defined disc and cup margins on the disc photographs was used for comparison. Seven ONH parameters, disc area, rim area, rim volume, cup area, cup volume, cup-to-disc (C/D) area ratio, and vertical C/D ratio, were computed based on both machine- and expert-defined margins and compared between the methods.
  
  
  RESULTS
  All automated ONH measurements showed good correlation with the expert defined margins (Pearson r = 0.90, disc area; 0.56, rim area; 0.78, rim volume; 0.88, cup area; 0.93, cup volume; 0.69, C/D area ratio; and 0.67, vertical C/D ratio; all P <or= 0.0001). No statistically significant difference was found in the glaucoma-discriminating ability of all seven ONH parameters (P >or= 0.21). The mean or median of automatically defined disc and cup areas was significantly higher than the subjective assessment (disc area P = 0.0001, t-test; cup area P = 0.036, Wilcoxon signed ranks test), although they had high correlation coefficients. The software failed to detect the disc margin for all the disc photographs with peripapillary atrophy.
  
  
  CONCLUSIONS
  The automated ONH analysis method provides an objective and quantitative ONH evaluation using widely available stereo disc photographs.
authors.affiliation: UPMC Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Juan
authors.initials: J
authors.lastname: Xu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishikawa
authors.forename: Gadi
authors.initials: G
authors.lastname: Wollstein
authors.forename: Richard A
authors.initials: RA
authors.lastname: Bilonick
authors.forename: Kyung R
authors.initials: KR
authors.lastname: Sung
authors.forename: Larry
authors.initials: L
authors.lastname: Kagemann
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Townsend
authors.forename: Joel S
authors.initials: JS
authors.lastname: Schuman
mesh_terms: D000465:Algorithms; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D010781:Photography / Q000379:methods*