Posterior choroidal boundary morphology and segmentation errors influence on choroidal thickness assessment in diabetic patients – a swept-source OCT study

Objective: to evaluate the choroidal morphology and choroidal thickness (CT) in normal and diabetic subjects and to compare the differences between automated segmentation (AS) and manual segmentation (MS) of the choroid. Methods: in this observational cross-sectional study we included 48 eyes: 24 normal eyes (group 1), 9 eyes with DM without diabetic retinopathy (DR) (group 2) and 15 eyes with DM and DR (group 3). Swept-source OCT line scans images were analyzed for the presence of the suprachoroidal layer (SCL), choroidal morphology and the CT was measured manually subfoveal and at 750 μ both nasal and temporal to the fovea after AS and MS. SCL was not included in the CT evaluation. CT values were compared between the groups and between the three points of evaluation. Results: SCL was visualized in 21 eyes (43.8%). In diabetic patients, SCL was visible in 11 (45.83%) cases and in nondiabetic patients, in 10 eyes (41.66%). There was a good AS of Bruch’s membrane, which was not further corrected manually. There were statistically significant differences between AS and MS at the level of CSJ for all three locations in all three groups (P ≤ 0.01). After MS, the choroid was statistically significantly thicker. Group 2 and group 3 showed a higher CT thickness. There were no statistically significant differences in the CT between groups in all three locations. Conclusions: Defining posterior choroidal boundary and the applied segmentation method can result in differences in CT measurements. Diabetic patients have altered CT and choroidal morphology. Abbreviations: CT = choroidal thickness, AS = automated segmentation, MS = manual segmentation, CSJ = choroidoscleral junction, SCL = suprachoroidal layer, SCS = suprachoroidal space, DM = diabetes mellitus, DR = diabetic retinopathy, RPE = retinal pigmented epithelium, BM = Buch’s membrane