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Yijun Huang, Anne Goulding, Sheri G. Alexander, Jeong W. Pak, Sapna Gangaputra, Larry D. Hubbard, Amitha Domalpally, Qian Peng, Ronald P. Danis; A Comparison Of Macular Thickness Measurements For Different OCT Devices After Data Standardization And Common Segmentation Method. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1017.
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To determine inter-device variability of macular thickness measurements among different Optical Coherence Tomography (OCT) instruments after the data format was standardized and a common computer-assisted manual segmentation used.
OCT scans were obtained from the maculae of both eyes in 4 normal subjects using 4 OCT devices, 3 spectral domain and 1 time domain. 3D cube, and 6-line radial scans (when available in the OCT devices), were performed. Repetitions of 3 scans were obtained for each scanning pattern. Images were then exported, normalized, and converted to DICOM OPT format, and viewed and analyzed in a custom software program. Boundary locations corresponding to the presumed inner limiting membrane (ILM), inner/outer segment junction (IS/OS), anterior border of retinal pigment epithelium (RPE), and Bruch’s membrane (BM) were manually identified by trained graders, and the layer boundaries were fit using spline interpolation. Mean values of the ILM-IS/OS, ILM-RPE, and ILM-BM thicknesses were calculated at the central and the inner subfields of the ETDRS-style macular grid (comprising 1, 3, 6mm concentric circles).
Using this standardization approach, the retinal thickness measurements are comparable among different OCT devices. The ranges of the mean thicknesses in the central field were: ILM-IS/OS, 178-221µm; ILM-RPE, 212-257µm; and ILM-BM, 251-302µm. The within-subject standard deviation were: ILM-IS/OS, 12.0µm centrally (C) and 9.6-12.7µm for the inner (IN) subfields; ILM-RPE, 11.9µm(C) and 8.9-14.6µm(IN); and ILM-BM, 12.4µm(C) and 10.1-16.7µm(IN).
Thickness measurements of retinal layers from different OCT devices are comparable in normal subjects when (1) identical definitions of outer retinal boundaries are used, (2) the OCT images are standardized and analyzed in a common analysis platform, and (3) a computer assisted manual segmentation procedure is applied uniformly. With careful standardization of OCT images and layer segmentation method, OCT retinal thickness measurement from different devices may be pooled in multi-center clinical trials. Studies in patients with retinal diseases are required to further substantiate this approach.
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