title: Reproducibility of nerve fiber layer thickness measurements using optical coherence tomography.
abstract: OBJECTIVE
  Optical coherence tomography (OCT) is a new technology that uses near-infrared light in an interferometer to produce approximately 10-microns resolution cross-sectional images of the tissue of interest. The authors performed repeated quantitative assessment of nerve fiber layer thickness in individuals with normal and glaucomatous eyes, and they evaluated the reproducibility of these measurements.
  
  
  METHODS
  The authors studied 21 eyes of 21 subjects by OCT. Each subject underwent five repetitions of a series of scans on five separate occasions within a 1-month period. Each series consisted of three circular scans around the optic nerve head (diameters, 2.9, 3.4, and 4.5 mm). Each series was performed separately using internal (fixation with same eye being studied) and external (fixation with contralateral eye) fixation techniques. The eye studied and the sequence of testing were assigned randomly.
  
  
  RESULTS
  Internal fixation (IF), in general, provides a slightly higher degree of reproducibility than external fixation (EF). Reproducibility was better in a given eye on a given visit than from visit to visit. Reproducibility as measured by intraclass correlation coefficients were as follows: circle diameter (CD), 2.9 mm, 0.51/0.57 (normal/glaucoma) (IF), 0.43/0.54 (EF); CD, 3.4 mm, 0.56/0.52 (IF), 0.43/0.61 (EF); CD, 4.5 mm, 0.53/0.43 (IF), 0.42/0.49 (EF).
  
  
  CONCLUSIONS
  Nerve fiber layer thickness can be reproducibly measured using OCT. Internal is superior to external fixation; each circle diameter tested provides adequate reproducibility.
authors.affiliation: New England Eye Center, Tufts University School of Medicine, Boston, MA 02111, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Schuman
authors.forename: T
authors.initials: T
authors.lastname: Pedut-Kloizman
authors.forename: E
authors.initials: E
authors.lastname: Hertzmark
authors.forename: M R
authors.initials: MR
authors.lastname: Hee
authors.forename: J R
authors.initials: JR
authors.lastname: Wilkins
authors.forename: J G
authors.initials: JG
authors.lastname: Coker
authors.forename: C A
authors.initials: CA
authors.lastname: Puliafito
authors.forename: J G
authors.initials: JG
authors.lastname: Fujimoto
authors.forename: E A
authors.initials: EA
authors.lastname: Swanson
mesh_terms: D000368:Aged; D005260:Female; D005654:Fundus Oculi; D005901:Glaucoma / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D009412:Nerve Fibers / Q000473:pathology*; D009900:Optic Nerve / Q000473:pathology*; D015203:Reproducibility of Results; D012160:Retina / Q000473:pathology*; D014054:Tomography / Q000379:methods*; D014794:Visual Fields