title: Diagnostic capability of optical coherence tomography in evaluating the degree of glaucomatous retinal nerve fiber damage.
abstract: OBJECTIVE
  To evaluate the role and ability of optical coherence tomography (OCT) to detect differences in peripapillary retinal nerve fiber layer (RNFL) thickness between normal and glaucomatous eyes and also between different severities of glaucoma.
  
  
  METHODS
  This cross-sectional observational study included 160 eyes of 160 healthy subjects and 134 eyes of 134 patients with primary open-angle glaucoma (POAG). Peripapillary RNFL thickness was measured on OCT using the fast RNFL thickness protocol. The RNFL thickness parameters used for evaluation included average RNFL thickness and inferior, superior, nasal, and temporal RNFL thickness. The glaucomatous eyes were subdivided into three subgroups on the basis of visual field defects and a fourth subgroup of eyes blinded by glaucoma. RNFL thickness parameters were compared among the normal eyes and the glaucoma subgroups. Correlation of global visual field indices with RNFL thickness parameters was also performed.
  
  
  RESULTS
  The average RNFL in control subjects, early glaucoma, moderate glaucoma, severe glaucoma, and blind glaucoma were 102.30 +/- 10.34, 77.68 +/- 15.7, 66.07 +/- 15.5, 53.65 +/- 14.2, and 44.93 +/- 4.95 microm, respectively. There was a significant difference in all RNFL thickness parameters between normal and all glaucoma subgroups (P < 0.001). Average and inferior RNFL thicknesses showed the highest area under the receiver operating characteristic curve, with 0.905 and 0.862 for normal versus early glaucoma, 0.705 and 0.722 for early versus moderate glaucoma, 0.737 and 0.717 for moderate versus severe glaucoma, and 0.635 and 0.584 for severe versus blind glaucoma. Both mean deviation (MD) and corrected pattern standard deviation (CPSD) showed a significant correlation with all the RNFL thickness parameters in eyes with glaucoma (P < 0.001).
  
  
  CONCLUSIONS
  RNFL thickness measured on OCT may serve as useful adjuncts in accurately and more objectively distinguishing normal from glaucomatous eyes, even in the early stages of glaucoma and may help to differentiate various severities of glaucoma. Average and inferior RNFL thicknesses are among the most efficient parameters for distinguishing such a differentiation. RNFL thicknesses in eyes blinded by glaucoma provide an estimate of the component of the RNFL thickness, which is not related to visual function.
authors.affiliation: Glaucoma Research Facility, Dr. Rajendra Prasad Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi. rjsihota@hotmail.com
authors.forename: Ramanjit
authors.initials: R
authors.lastname: Sihota
authors.forename: Parul
authors.initials: P
authors.lastname: Sony
authors.forename: Viney
authors.initials: V
authors.lastname: Gupta
authors.forename: Tanuj
authors.initials: T
authors.lastname: Dada
authors.forename: Rajvir
authors.initials: R
authors.lastname: Singh
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D005902:Glaucoma, Open-Angle / Q000145:classification / Q000175:diagnosis*; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000145:classification / Q000175:diagnosis*; D012372:ROC Curve; D012165:Retinal Ganglion Cells / Q000473:pathology*; D041623:Tomography, Optical Coherence / Q000379:methods*; D014786:Vision Disorders / Q000175:diagnosis; D014794:Visual Fields