title: Repeatability of nerve fiber layer thickness measurements in patients with glaucoma and without glaucoma using spectral-domain and time-domain OCT.
abstract: BACKGROUND
  The aim of this work is to assess the repeatability of spectral-domain-OCT (SD-OCT) retinal nerve fiber layer thickness (RNFL) thickness measurements in a non-glaucoma group and patients with glaucoma and to compare these results to conventional time-domain-OCT (TD-OCT).
  
  
  METHODS
  In a prospective, comparative, observational case-control study, 50 eyes of 25 non-glaucoma and 22 eyes of 11 patients with primary open angle glaucoma (POAG) were included. SD-OCT and TD-OCT circle scans were centered on the optic disc. In each eye, OCT scans were performed three times by two independent observers. RNFL thickness was measured in four quadrants around the optic disc. In addition, the overall mean RNFL thickness was assessed. Intraclass correlation coefficients (ICC) and coefficients of variation (COV) were calculated. Inter-observer and inter-OCT repeatability was visualized by using Bland-Altman analysis.
  
  
  RESULTS
  Intra-observer repeatability for TD- OCT was good with an ICC(mean RNFL thickness) of 0.939 in non-glaucomas and 0.980 in glaucomatous eyes. For SD-OCT, intra-observer repeatability was higher with an ICC of 0.989 for non-glaucomas and 0.997 for glaucomatous eyes. COVs for TD-OCT ranged from 2.9-7.7% in non-glaucomas and from 6.0-13.3% in glaucoma patients. COVs for SD-OCT ranged from 0.3-1% in non-glaucomas and from 0.9-2.3% in glaucomatous eyes. COVs were influenced by various factors. In the glaucoma group, COVs were significantly higher (p < 0.001) compared to the non-glaucoma group. COVs increased by a mean of 5.1% when TD-OCT was used instead of SD-OCT (p < 0.001).
  
  
  CONCLUSIONS
  SD-OCT RNFL thickness measurements in healthy volunteers and glaucoma patients showed good intra- and inter-observer repeatability. Especially in glaucomatous eyes, repeatability of SD-OCT was superior to TD-OCT.
authors: Division of Ophthalmology, UniversityHospital Zurich, Frauenklinikstrasse 24, 8091 Zurich, Switzerland. marc.toeteberg@usz.ch
authors: Marc
authors: M
authors: Töteberg-Harms
authors: Veit
authors: V
authors: Sturm
authors: Pascal B
authors: PB
authors: Knecht
authors: Jens
authors: J
authors: Funk
authors: Marcel N
authors: MN
authors: Menke
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D008297:Male; D009412:Nerve Fibers / Q000473:pathology*; D015588:Observer Variation; D009898:Optic Disk / Q000473:pathology*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012165:Retinal Ganglion Cells / Q000473:pathology*; D013997:Time Factors; D041623:Tomography, Optical Coherence