title: Retinal Nerve Fiber Layer Converges More Convexly on Normal Smaller Optic Nerve Head.
abstract: OBJECTIVE
  To investigate retinal nerve fiber layer (RNFL) configuration in the optic nerve head (ONH) and peripapillary area according to disc size and to determine whether it explains cup discrepancy among eyes with different disc sizes.
  
  
  METHODS
  Horizontal and vertical RNFL curvature and mean thickness were measured using confocal scanning laser ophthalmoscopy (Heidelberg Retina Tomograph) in 63 normal subjects grouped by disc size. Average and quadrant RNFL thickness, disc size, average cup-to-disc ratio (CDR), and convergence angle at the optic disc were also measured using Cirrus HD-optical coherence tomography. The relationships between disc size and RNFL curvature, thickness, angle at optic disc, and CDR were evaluated. RNFL curvature and convergence angle reflects convexity "on" and "into" the optic disc, respectively.
  
  
  RESULTS
  CDR was smaller for small discs and was positively correlated with disc size (P<0.001). Horizontal and vertical RNFL curvatures were significantly more convex for small than large discs (P=0.001, 0.017). Horizontal and vertical RNFL angles at the optic disc were positively correlated with disc size (P<0.001, P=0.012). Optic disc area was negatively correlated with mean RNFL thickness at the optic disc margin measured by HRT (P=0.002), but not in the peripapillary area by optical coherence tomography.
  
  
  CONCLUSIONS
  Using imaging techniques, we demonstrated that the shape of the RNFLs converging "on" and entering "into" the optic disc was more convex for small optic discs compared with large discs. A low CDR for small discs could be mediated by these RNFL profiles at the ONH, which may guide the clinical evaluation of glaucomatous ONH damage.
authors.affiliation: Department of Ophthalmology and Visual Science, Seoul St Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Kyoung In
authors.initials: KI
authors.lastname: Jung
authors.forename: Jeong Ah
authors.initials: JA
authors.lastname: Shin
authors.forename: Hae-Young Lopilly
authors.initials: HY
authors.lastname: Park
authors.forename: Chan Kee
authors.initials: CK
authors.lastname: Park
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers; D009887:Ophthalmoscopy; D009898:Optic Disk / Q000033:anatomy & histology*; D012165:Retinal Ganglion Cells / Q000166:cytology*; D041623:Tomography, Optical Coherence / Q000379:methods; D014792:Visual Acuity / Q000502:physiology