title: Estimating Lead Time Gained by Optical Coherence Tomography in Detecting Glaucoma before Development of Visual Field Defects.
abstract: OBJECTIVE
  To estimate the diagnostic accuracy and lead time gained by retinal nerve fiber layer (RNFL) thickness measurements from optical coherence tomography (OCT) for detecting glaucoma before the development of visual field defects.
  
  
  METHODS
  Observational cohort study.
  
  
  METHODS
  The study group included 75 eyes of 75 patients suspected of having glaucoma. These eyes had normal standard automated perimetry (SAP) at baseline and demonstrated repeatable (3 consecutive) abnormal tests during a median follow-up of 6.3 years. A control group of 75 eyes of 75 healthy subjects matched by age and number of OCT tests during follow-up was included.
  
  
  METHODS
  The RNFL thickness measurements were obtained at the time of development of the earliest SAP defect (time 0) and also at times -1, -2, -3, and so forth, corresponding to 1 year, 2 years, 3 years, and so forth, before the development of field loss. The OCT measurements at corresponding intervals were analyzed for controls. Time-dependent receiver operating characteristic (ROC) curves were used to evaluate diagnostic accuracy of OCT.
  
  
  METHODS
  Areas and sensitivities of ROC curve at fixed specificities at different times before development of field loss.
  
  
  RESULTS
  At the date of conversion to the earliest visual field defect (time 0), mean ± standard deviation average RNFL thickness was 75.0±9.8 μm in glaucomatous eyes and 90.6±8.0 μm for controls (P < 0.001). Significant differences were seen up to 8 years before development of visual field defects (86.3±8.2 μm vs. 91.4±7.6 μm, respectively; P = 0.021). The ROC curve areas decreased with increasing times before detection of field defects. At times 0, -4, and -8 years, ROC curve areas were 0.87, 0.77, and 0.65, respectively. At 95% specificity, up to 35% of eyes had abnormal average RNFL thickness 4 years before development of visual field loss and 19% of eyes had abnormal results 8 years before field loss.
  
  
  CONCLUSIONS
  Assessment of RNFL thickness with OCT was able to detect glaucomatous damage before the appearance of visual field defects on SAP. In many subjects, significantly large lead times were seen when applying OCT as an ancillary diagnostic tool.
authors.affiliation: Hamilton Glaucoma Center and Department of Ophthalmology, University of California, San Diego, La Jolla, California; Department of Ophthalmology, Taipei Veterans General Hospital, Taipei, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Tammy M
authors.initials: TM
authors.lastname: Kuang
authors.affiliation: Hamilton Glaucoma Center and Department of Ophthalmology, University of California, San Diego, La Jolla, California; Department of Ophthalmology, First Affiliated Hospital, Harbin Medical University, Harbin, China.
authors.forename: Chunwei
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Hamilton Glaucoma Center and Department of Ophthalmology, University of California, San Diego, La Jolla, California.
authors.forename: Linda M
authors.initials: LM
authors.lastname: Zangwill
authors.affiliation: Hamilton Glaucoma Center and Department of Ophthalmology, University of California, San Diego, La Jolla, California.
authors.forename: Robert N
authors.initials: RN
authors.lastname: Weinreb
authors.affiliation: Hamilton Glaucoma Center and Department of Ophthalmology, University of California, San Diego, La Jolla, California. Electronic address: fmedeiros@ucsd.edu.
authors.forename: Felipe A
authors.initials: FA
authors.lastname: Medeiros
mesh_terms: D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006068:Gonioscopy; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D012372:ROC Curve; D012165:Retinal Ganglion Cells / Q000473:pathology*; D013997:Time Factors; D041623:Tomography, Optical Coherence; D014786:Vision Disorders / Q000175:diagnosis*; D058609:Visual Field Tests; D014794:Visual Fields