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Parvathi T. hari, Rajesh S. Kumar, Sathi Devi A.V, Ramgopal Balu, Narendra K.P, Dhanraj Rao, Rohit Shetty, Bhujang K. Shetty; Agreement between Spectral domain and Time domain OCT for Assessing Retinal Nerve Fiber Layer Thickness Measurements. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1166.
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To determine the agreement between the retinal nerve fiber layer (RNFL) thickness measurements from the Stratus Time domain Optical Coherence Tomography (OCT) and the Spectralis Spectral Domain OCT.
Peripapillary RNFL thickness was measured with the Stratus OCT and the Spectralis OCT in both eyes on the same day of each subject to determine agreement. Two operators used the same instruments for all scans. Bland- Altman plots were used to assess agreement between the two devices.
A total of 232 eyes (147 subjects) of normals and subjects with glaucoma were analyzed. The subjects were divided into groups based on visual field criteria: normal (n =129), early glaucoma (n = 42), moderate glaucoma (n =35) and severe glaucoma (n= 26). The average age of glaucoma subjects was significantly higher than normal subjects: 60.71 ±13.89 years versus 43.27 ± 16.57 years (p<0.001). For Stratus OCT, the average RNFL values was 102.4 ± 10.17 µ, 82.29 ± 11.9 µ, 73.45 ± 12.9 µ, 56.54 ± 11.36 µ in the normal, early, moderate and severe glaucoma groups, respectively. The corresponding values for the Spectralis were 99.7 ± 9.6 µ, 80.2± 10.7 µ, 72.48± 12.2 µ and 55.8 ± 12.8 µ. The Stratus - Spectralis differences were not significant except in the normal group p = 0.02. Quadrant wise Bland - Altman plot analysis showed a systematic difference in measuring RNFL thickness between the 2 devices; Spectralis underestimated thinner RNFL and overestimated thicker RNFL compared to Stratus OCT.
Spectralis and Stratus RNFL thickness measurements cannot be used interchangeably. Spectralis measurements appear to be smaller at thinner RNFL and should be interpreted with caution in severe disease.
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