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Hemal Mehta, Dawn A. Sim, Pearse A. Keane, Javier Zarranz-Ventura, Becky Smith, Marcus Fruttiger, Praveen J. Patel, Catherine A. Egan, Adnan Tufail; The Diabetic Retinopathy Repair Project - Reproducibility of EDI OCT Measurements in Manual Segmentation of Novel Choroidal Sub-Layers of Diabetic patients. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2130.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the reproducibility of detailed manual choroidal segmentation of enhanced depth imaging (EDI) optical coherence tomography (OCT).
10 eyes of 10 subjects with diabetic eye disease were analysed. All subjects were imaged centred on the fovea with custom EDI scanning protocols consisting of 13 OCT B-scans obtained in a 20 x 15 degree horizontal raster pattern, and with each individual B-scan generated from 100 averaged scans. Detailed segmentation was performed to quantify the retina and choroidal layers. Further segmentation of the choroidal layer in to Haller’s large vessel and Sattler’s medium vessel layers was performed in Early Treatment Diabetic Retinopathy Study (ETDRS) subfields 1-9. Images were segmented by an experienced and inexperienced grader. Data analysis was performed by a third party. The methods of Bland and Altman were used to calculate the mean difference between graders. The reproducibility of thickness and volume measurements were quantified using bias (mean difference) and analysed by the concordance coefficient with a 95% confidence interval.
Retinal and total choroidal thickness and volumes were highly correlated (r=0.99, p<0.0001) but Haller’s layer thickness showed weaker correlation (r=0.75, p-0.01). The 95% limits of agreement were among retinal, total choroidal thickness and its sub-layers in EDTRS areas 1-9 were -2.3% to -0.7% (bias -1.5%, p=0.003) in retina thickness, 3.2% to 13.2% (bias 8.2%, p=0.005) in total choroidal thickness, and -37.3% to 8.2% (bias 14.6%, p=0.18) in Haller’s large vessel layer. Close agreement was found between retinal thickness and volume measurements but bias was in the choroid which increased with sub-layer segmentation.
These preliminary results suggest that total retinal and total choroidal thickness can be measured with good reproducibility, although detailed analysis of choroidal sub-layers (e.g. Haller's layer) was less reproducible. Further training with introduction of standardised choroidal grading conventions, may allow reproducible quantification of these sub-layers - analysis of such parameters may be useful for a number of posterior segment diseases.
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