title: An analysis of normal variations in retinal nerve fiber layer thickness profiles measured with optical coherence tomography.
abstract: OBJECTIVE
  To assess the normal variations in retinal nerve fiber layer (RNFL) thickness measured with optical coherence tomography (OCT).
  
  
  METHODS
  Both eyes of 48 individuals (age 56.4+/-9.5 y) with normal vision and refractive errors between +/-6.0 D were tested with the fast RNFL scan protocol of the OCT3 (Zeiss Meditech). Their 256-point RNFL profiles were exported for analysis. The location and peak amplitude of the maxima of the RNFL profiles were measured. Intersubject and interocular variations were assessed with a coefficient of determination, R2. An R2 of 1.0 indicated that the average profile from all 48 individuals (or of the 2 eyes) accounted for 100% of the variation of an individual eye's profile.
  
  
  RESULTS
  The R2 for the interocular comparison was good, with averages of 0.91+/-0.07 (right eye) and 0.92+/-0.05 (left eye). The R2 for the comparison of the individual's profile to the mean group profile was only 0.61+/-0.29 (right eye) and 0.65+/-0.24 (left eye), with 27% of the R2 values below 0.5. Even after normalizing each individual's profile by its mean, R2 was only 0.75+/-0.16 (0.75+/-0.16) for the right (left) eye. The location of the peaks for the right (left) eye ranged over 91 degrees (88 degrees) for the superior peak and over 64 degrees (66 degrees) for the inferior peak. The range of peak amplitudes for the right (left) eye spanned a factor of 1.7 (1.8) and 2.0 (1.7) for the superior and inferior peaks, respectively.
  
  
  CONCLUSIONS
  There was a wide variation in the amplitude and shape of the individual RNFL profiles. However, the RNFL profiles of the 2 eyes of an individual were extremely similar. Adding an interocular comparison with OCT RNFL tests should help identify some false positives.
authors.affiliation: Department of Psychology, Columbia University, New York, NY 10027, USA.
authors.forename: Quraish
authors.initials: Q
authors.lastname: Ghadiali
authors.forename: Donald C
authors.initials: DC
authors.lastname: Hood
authors.forename: Clara
authors.initials: C
authors.lastname: Lee
authors.forename: Jack
authors.initials: J
authors.lastname: Manns
authors.forename: Alex
authors.initials: A
authors.lastname: Llinas
authors.forename: Larissa K
authors.initials: LK
authors.lastname: Grover
authors.forename: Vivienne C
authors.initials: VC
authors.lastname: Greenstein
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Liebmann
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Odel
authors.forename: Robert
authors.initials: R
authors.lastname: Ritch
mesh_terms: D000328:Adult; D000368:Aged; D001369:Axons; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012165:Retinal Ganglion Cells / Q000166:cytology*; D012680:Sensitivity and Specificity; D041623:Tomography, Optical Coherence / Q000379:methods*; D014792:Visual Acuity