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S. Bhartiya, M. Kumar, V. Kumar, S. Khanduja, S. K. Mishra, T. Dada; Comparison of Time Domain and Spectral Domain Optical Coherence Tomography in Retinal Nerve Fiber Layer Thickness Measurements. Invest. Ophthalmol. Vis. Sci. 2010;51(13):245.
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To compare retinal nerve fiber layer (RNFL) measurements by two optical coherence tomography (OCT) systems: the Stratus time domain OCT and the Cirrus spectral domain OCT (both by Carl Zeiss Meditec, Dublin, CA).
40 patients of primary open angle glaucoma and 40 healthy controls were enrolled in this observational cross-sectional study. Participants were imaged by a single trained operator using the Stratus OCT (fast RNFL scan mode) and Cirrus HD-OCT (optic disc cube mode) at the same visit. The order of the machines was randomized and the RNFL thicknesses measured by the two instruments were compared. A randomly selected eye of each of the participants was used for statistical analysis.. Reliability was assessed by the Intra-class correlation coefficient (ICC) and the Bland Altman plot for the limits of agreement for the overall mean RNFL thickness as well as for each quadrant.
The mean temporal, superior, nasal and inferior RNFL thickness as measured by the two machines are described in Table 1.ICC for the temporal, superior, nasal and inferior quadrant RNFL thickness measurements were 0.82, 0.85, 0.64 and 0.92 respectively. Bland Altman plots showed the limits of agreement (95%CI) for average RNFL to be -24.68 to 15.50 in the control group. In patients of glaucoma, Bland-Altman plots showed the limits of agreement (95%CI) for average RNFL to be -18.38 to 23.58.
There were clinically significant differences in the RNFL thickness measurements as determined by Stratus OCT and Cirrus HD-OCT. These two machines may not be used interchangeably during longitudinal follow-up of glaucoma patients and normal individuals.
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