title: Predicted and measured retinal nerve fiber layer thickness from time-domain optical coherence tomography compared with spectral-domain optical coherence tomography.
abstract: OBJECTIVE
  New methods are needed to compare peripapillary retinal nerve fiber layer thickness (pRNFLT) measurements taken from time-domain optical coherence tomography (TD-OCT) and spectral-domain OCT (SD-OCT).
  
  
  OBJECTIVE
  To compare the agreement of measured and predicted pRNFLT using different equations based on pRNFLT measurements obtained by TD-OCT and SD-OCT.
  
  
  METHODS
  Cross-sectional single-center study that took place at the Department of Ophthalmology, University of Erlangen-Nuremberg from November 16, 2005, to June 3, 2015, and included 138 eyes of control participants, 126 eyes of patients with ocular hypertension, 128 eyes of patients with preperimetric glaucoma, and 160 eyes of patients with perimetric glaucoma. All participants had standard clinical examinations to obtain TD-OCT (via Stratus OCT) and SD-OCT (via Spectralis OCT) measurements of pRNFLT. Two groups were matched for diagnostic subgroup, eye side, sex, and age. The TD-OCT measurements of the first group were used to predict the mean SD-OCT and 6-sector vertical-split pRNFLT measurements of the second group and vice versa. The agreement between the predicted pRNFLT calculations of conversion equations and measured pRNFLT of the second group was evaluated by intraclass correlation coefficients and Bland-Altman plots.
  
  
  METHODS
  Mean and sectoral pRNFLT measurements obtained by TD-OCT and SD-OCT as well as the agreement between measured and predicted pRNFLT.
  
  
  RESULTS
  The agreement for all investigated equations to predict mean pRNFLT measurements with intraclass correlation coeffecients ranged from 0.937 to 0.939. Bland-Altman plots demonstrated systemic biases between -0.7 μm and +1.1 μm for measured and predicted mean pRNFLT measurements. The ratio method demonstrated an intraclass correlation coefficient of 0.969 for the temporal-inferior sector. The best color-code agreement between both OCT devices was achieved by the no conversion method, with κ = 0.731 (95% CI, 0.656-0.806) for the mean pRNFLT.
  
  
  CONCLUSIONS
  These data suggest that the prediction of mean pRNFLT values by equations derived from TD-OCT and SD-OCT can be conducted with high levels of agreement. In individual cases and singular sectors, high prediction errors may occur. When longitudinal imaging data from both TD-OCT and SD-OCT are available, conversion equations may provide longitudinal comparability.
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Schrems
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Schrems-Hoesl
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Delia
authors.initials: D
authors.lastname: Bendschneider
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Christian Y
authors.initials: CY
authors.lastname: Mardin
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Laemmer
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Friedrich E
authors.initials: FE
authors.lastname: Kruse
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Folkert K
authors.initials: FK
authors.lastname: Horn
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005188:False Negative Reactions; D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D006068:Gonioscopy; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009798:Ocular Hypertension / Q000175:diagnosis; D009898:Optic Disk / Q000473:pathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012165:Retinal Ganglion Cells / Q000473:pathology*; D013997:Time Factors; D041623:Tomography, Optical Coherence / Q000295:instrumentation / Q000379:methods*; D014065:Tonometry, Ocular; D058609:Visual Field Tests