title: Agreement for detecting glaucoma progression with the GDx guided progression analysis, automated perimetry, and optic disc photography.
abstract: OBJECTIVE
  To evaluate the ability of the GDx Variable Corneal Compensation (VCC) Guided Progression Analysis (GPA) software for detecting glaucomatous progression.
  
  
  METHODS
  Observational cohort study.
  
  
  METHODS
  The study included 453 eyes from 252 individuals followed for an average of 46+/-14 months as part of the Diagnostic Innovations in Glaucoma Study. At baseline, 29% of the eyes were classified as glaucomatous, 67% of the eyes were classified as suspects, and 5% of the eyes were classified as healthy.
  
  
  METHODS
  Images were obtained annually with the GDx VCC and analyzed for progression using the Fast Mode of the GDx GPA software. Progression using conventional methods was determined by the GPA software for standard automated achromatic perimetry (SAP) and by masked assessment of optic disc stereophotographs by expert graders.
  
  
  METHODS
  Sensitivity, specificity, and likelihood ratios (LRs) for detection of glaucoma progression using the GDx GPA were calculated with SAP and optic disc stereophotographs used as reference standards. Agreement among the different methods was reported using the AC(1) coefficient.
  
  
  RESULTS
  Thirty-four of the 431 glaucoma and glaucoma suspect eyes (8%) showed progression by SAP or optic disc stereophotographs. The GDx GPA detected 17 of these eyes for a sensitivity of 50%. Fourteen eyes showed progression only by the GDx GPA with a specificity of 96%. Positive and negative LRs were 12.5 and 0.5, respectively. None of the healthy eyes showed progression by the GDx GPA, with a specificity of 100% in this group. Inter-method agreement (AC(1) coefficient and 95% confidence intervals) for non-progressing and progressing eyes was 0.96 (0.94-0.97) and 0.44 (0.28-0.61), respectively.
  
  
  CONCLUSIONS
  The GDx GPA detected glaucoma progression in a significant number of cases showing progression by conventional methods, with high specificity and high positive LRs. Estimates of the accuracy for detecting progression suggest that the GDx GPA could be used to complement clinical evaluation in the detection of longitudinal change in glaucoma.
authors.affiliation: Hamilton Glaucoma Center, Department of Ophthalmology, University of California San Diego, La Jolla, California 92093-0946, USA.
authors.forename: Luciana M
authors.initials: LM
authors.lastname: Alencar
authors.forename: Linda M
authors.initials: LM
authors.lastname: Zangwill
authors.forename: Robert N
authors.initials: RN
authors.lastname: Weinreb
authors.forename: Christopher
authors.initials: C
authors.lastname: Bowd
authors.forename: Gianmarco
authors.initials: G
authors.lastname: Vizzeri
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Sample
authors.forename: Remo
authors.initials: R
authors.lastname: Susanna
authors.forename: Felipe A
authors.initials: FA
authors.lastname: Medeiros
mesh_terms: D018450:Disease Progression; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis* / Q000503:physiopathology; D006068:Gonioscopy; D006801:Humans; D007429:Intraocular Pressure; D016013:Likelihood Functions; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis / Q000503:physiopathology; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis* / Q000503:physiopathology; D010781:Photography / Q000379:methods*; D011446:Prospective Studies; D015203:Reproducibility of Results; D057109:Scanning Laser Polarimetry / Q000379:methods*; D012680:Sensitivity and Specificity; D058609:Visual Field Tests / Q000379:methods*