To evaluate the impact of segmentation error correction on retinal layers thickness and retinal vessel density measurements.

Macular Optical Coherence Tomography (OCT) and Optical Coherence Tomography Angiography (OCTA) scans of eyes from 45 subjects (25 subject with diabetes and 20 subject who was normal) that were obtained through a dilated pupil using the RTVue Avanti spectral-domain optical coherence tomography system with the AngioVue software (Version 2016.1.0.26; Optovue, Inc, Fremont, CA) were evaluated by two independent person for segmentation error and this artifact were corrected manually. Level of agreement between rater was assessed. The frequency of segmentation error was compared between scans of two groups. Retinal layers thickness and vessel density of retinal layers in the foveal and parafoveal region also compared between two groups and before and after correction.

All scans of patients with diabetes had macular edema in OCT. Intraclass correlation coefficients (ICC) demonstrated excellent inter-grader agreement (ICC ≥ 0.9) in all parameters of both groups. All scans of diabetic eyes need correction and only 15% of healthy eyes need segmentation correction. Segmentation error in outer plexiform layer slabs was more common than the inner plexiform layer in both groups. After segmentation error correction, retinal layers thickness changes weren't significantly different. Comparison of the absolute changes between diabetic and control groups revealed that all parameter other than parafoveal deep vessel density changed significantly. (P<0.05)

Segmentation error in OCT scans of patients with diabetic macular edema is common. This artifact is less common in the scans of healthy subjects. Correcting retinal segmentation error significantly change vessel density of deep plexus in the parafoveal region of diabetic patients but not retinal layer thickness. Thickness and vessel density of normal subjects didn't change significantly after correction of segmentation error.