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J. Kim, J. Xu, H. Ishikawa, K. Sung, G. Wollstein, R. A. Bilonick, L. Kagemann, J. S. Duker, J. G. Fujimoto, J. S. Schuman; RNFL Reproducibility Improved With 3D Spectral Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3763.
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© ARVO (1962-2015); The Authors (2016-present)
To test reproducibility of retinal nerve fiber layer (RNFL) thickness measurement using Stratus OCT and Cirrus HD-OCT (Carl Zeiss Meditec, Inc., Dublin, CA). In addition, two methods for assessing Cirrus RNFL measurements were evaluated: defining the circle center in each image (MC) or using a universal center that was exported from one image to another (UC).
Twenty-seven eyes of 14 healthy subjects were enrolled. The peripapillary region was scanned 3 times for each eye with each device. Fast RNFL scan for Stratus and Glaucoma Basic Combo with 200x200x1024 samplings in 6.0x6.0x2.0 mm centered on optic nerve head (ONH) for Cirrus were obtained. Cirrus images were analyzed in two ways; 1) MC - ONH center was defined on each image separately, and 2) UC - ONH center was defined on one image and then exported to other 2 images after aligning images for horizontal and vertical shift. A 3.4 mm diameter virtual circle centered on the ONH was then resampled on Cirrus 3D OCT images using the resulting ONH center, and RNFL thickness was measured using software of our own design. Linear mixed effect models were used to compute the estimated measurement variability (EMV) with 95% confidence intervals for mean, quadrant, and clock hour RNFL thickness measurements.
EMV for mean RNFL was 2.51 µm (confidence interval: 1.59-3.96) for Stratus, 2.23 µm (1.86-2.67) for MC method, and 2.15 µm (1.39-3.34) for UC method. There was no statistically significant difference in EMV between MC and UC methods except for 9 o’clock. The UC method showed a significantly smaller EMV than Stratus in all measurements except for clock hours 3, 8, 9; these had a significantly larger EMV than Stratus. The MC method showed a significantly smaller EMV than Stratus in 2 quadrants (nasal and inferior) and 5 clock hours (1, 2, 6, 11, and 12) and a significantly larger EMV than Stratus at 9 o’clock.
Cirrus RNFL measurement generally showed better RNFL thickness measurement reproducibility than Stratus OCT. Having a universal center point may be advantageous in terms of better RNFL measurement reproducibility.
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