Optimizing the Information Yield of 3-D OCT in Glaucoma

PURPOSE. To determine, first, which regions of 3-D optical coherence tomography (OCT) volumes can be segmented completely in the majority of subjects and, second, the relationship between analyzed area and thickness measurement test-retest variability. METHODS. Three-dimensional OCT volumes (6X6 mm) centered around the fovea and optic nerve head (ONH) of 925 Rotterdam Study participants were analyzed; 44 participants were scanned twice. Volumes were segmented into 10 layers, and we determined the area where all layers could be identified in at least 95% (macula) or 90% (ONH) of subjects. Macular volumes were divided in 2 x 2, 4 x 4, 6 x 6, 8 x 8, or 68 blocks. We placed two circles around the ONH; the ONH had to fit into the smaller circle, an RESULTS. Eighty-two percent of the macular volume could be segmented in at least 95% of subjects; for the ONH, this was 65% in at least 90%. The radii of the circles were 1.03 and 1.84 mm. Depending on the analyzed area, median test-retest variability ranged from 8% to 15% for macular RNFL, 11% to 22% for macular RGCL, 5% to 11% for the two together, and 18% to 22% for ONH RNFL. CONCLUSIONS. Test-retest variability hampers a detailed analysis of 3-D OCT data. Combined macular RNFL and RGCL thickness averaged over larger areas had the best test-retest variability. (Invest Ophthalmol Vis Sci. 2012; 53: 8162-8171) DOI:10.1167/iovs.12-10551