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Amr Elsawy, Taher Kamel Eleiwa, Mariam Raheem, Giovanni Gregori, Mohamed Abdel-Mottaleb, Mohamed Abou Shousha; Segmentation of inner microlayers of abnormal cornea in Optical Coherence Tomography images using graph segmentation. Invest. Ophthalmol. Vis. Sci. 2019;60(11):024.
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© ARVO (1962-2015); The Authors (2016-present)
To report on a graph-based automated segmentation method to segment the epithelium, Bowmans (BW), Stroma (ST) and Descemets (DM) microlayers of abnormal cornea using high definition optical coherence tomography (HD-OCT) images.
Fifteen eyes were imaged using HD-OCT (Envisu R2210, Bioptigen, Buffalo Grove, IL, USA). These eyes had different diagnoses: Dry eye (2 eyes), Keratoconus (5 eyes), Fuchs Dystrophy (3 eyes), and controls (5 eyes). The 15 images were manually segmented by two expert operators. The automated segmentation algorithm segmented the Epithelium (EP) and the Endothelium (EN) microlayers and used them to segment the inner microlayers. A flat-EP image was obtained, and its vertical gradient was computed. A directed graph was used to segment the BW and ST as the two hyper-reflective microlayers after the EP. A flat-EN image was obtained and its vertical gradient was computed. A directed graph was used to segment the DM as the hyper-reflective microlayer before the EN. In both graphs, the edge energy included gradient energy and directional energy. Some of the segmentation results are shown in Fig. 1.
The epithelium, Bowmans, Stroma and Descemets microlayers of those abnormal corneas were successfully segmented using the graph method in all images. The inter-operator error between the two manual operators was 1.75±1.54 pixels for the epithelium, Bowmans, 1.73±1.43 for the Stroma and 3.10±2.28 for the Descemets (mean 2.17±1.88 pixels). The mean segmentation difference between the graph-based segmentation and the manual operators was 1.69±1.90 pixels for the epithelium, Bowmans, 2.47±3.15 pixels for the Stroma and 4.36±3.21 for the Descemets (mean 2.77±2.99 pixels). The segmentation results were comparable to the manual segmentation (see Fig. 2). The mean segmentation time for all microlayers in one image was 4.27±0.65 seconds and the segmentation had zero intra-operator error.
The proposed graph-based segmentation method, for segmenting corneal microlayers using HD-OCT images, was objectively comparable to the manual segmentation for abnormal and healthy corneas and it is significantly faster and repeatable.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.
Fig. 1 Examples of segmentation of inner corneal microlayers
Fig. 2 Segmentation difference comparison
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