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D. Baleanu, R. P. Tornow, F. K. Horn, R. Laemmer, F. E. Kruse, C. Y. Mardin; Comparison of Retinal Nerve Fiber Layer Thickness Measurements and Diagnostic Accuracy Between Spectral Domain and Time Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2010;51(13):251.
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© ARVO (1962-2015); The Authors (2016-present)
To compare peripapillary retinal nerve fiber layer (RNFL) thickness measurements between two optical coherence tomography (OCT) instruments (high resolution spectral domain (SD) OCT Spectralis, Heidelberg Engineering and time domain (TD) OCT Stratus OCT, Carl Zeiss Meditec) in healthy subjects and glaucoma patients and compare their diagnostic precision.
The RNFL of 104 healthy subjects and 138 glaucoma patients from Erlanger glaucoma registry was imaged on the same day with each OCT. RNFL thickness was measured with undilated pupils around the disc with 16 automatically averaged consecutive circular B-scans (3.4 mm diameter, 768 A-scans) using an online tracking system to compensate for eye movements for SD-OCT and with dilated pupils with 3 manually averaged 3.4 mm diameter circular B-scans for TD-OCT.One eye of each patient entered the study. RNFL thicknesses were calculated for 4 sectors (superior, nasal, inferior and temporal) for each OCT. RNFL thicknesses obtained by the two OCTs were compared. Receiver operating characteristics (ROC) curves were used to determine diagnostic precision.
Table 1 gives the mean values of RNFL thickness globally and in each of 4 sectors by diagnostic group and the comparison of global and sectoral RNFL thicknesses by SD- and TD-OCT. A good agreement between both OCTs was found for global RNFL thickness, the difference between SD and TD-OCT being within 10 µm in 95.2% of healthy eyes and in 86.9% of glaucomatous eyes.With both, SD- and TD-OCT, the highest ROC curve areas were found in the inferior sector (0.93 vs. 0.94) followed by global RNFL thickness (0.93 vs. 0.91).
In our study RNFL measurements by Spectralis- and Stratus-OCT showed good agreement and similar diagnostic precision. Because the limits of agreement are acceptable for clinical purposes RNFL measurements obtained from these two OCTs may be used interchangeably.As the resulting RNFL thickness depends on the algorithm used for segmentation, this might be different with other SD-OCT instruments.
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