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A comparison of structural measurements using 2 Stratus optical coherence tomography instruments.

Sehi M, Guaqueta DC, Feuer WJ, Greenfield DS

Department of Ophthalmology, University of Miami Miller School of Medicine, Bascom Palmer Eye Institute, Palm Beach Gardens, FL 33418, USA. msehi@med.miami.edu

PURPOSE: To compare measures of peripapillary retinal nerve fiber layer (RNFL) thickness, optic disc topography, and central foveal thickness generated using 2 different Stratus optical coherence tomography (OCT) instruments. METHODS: Ten normal subjects and 10 glaucoma subjects were included. One randomly selected eye per subject was scanned consecutively using a fast RNFL thickness protocol, fast macular thickness map, and fast optic disc protocol by 2 experienced operators on 2 instruments. The order of the machines and operators were randomized. The output power of each machine was measured using an optical power meter. For each OCT measurement 2 factor fixed effects analyses of variance were performed and a restricted maximum likelihood variance component analysis of the proportion of variance due to subject, operator, and machine was calculated. RESULTS: Significant differences (P<or=0.003) between OCT instruments were observed in average, superior, and inferior RNFL thickness and central foveal thickness values among normal eyes; and average and superior RNFL thickness and cup/disc area ratio values among glaucomatous eyes. Overall, the intermachine variability (0.0% to 16.4%) was larger than the interoperator variability (0.0% to 2.4%) for all OCT measurements. In the glaucoma group the variability due to machine differences was 2.6 microm for the average RNFL thickness, 5.7 microm for the superior RNFL thickness, 0 microm for the inferior RNFL thickness, 0.03 microm for the cup/disc area ratio, 0.01 microm for the cup/disc vertical ratio, and 2.8 microm for the average foveal thickness. CONCLUSIONS: Measurements of RNFL thickness, optic disc topography, and central foveal thickness significantly differ between OCT instruments.

Published 17 April 2007 in J Glaucoma, 16(3): 287-92.
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