Stromal area (SA=TCA-LA) and choroidal vascularity index (CVI=LA*100/TCA) (%) were calculated. Total choroidal area (TA) and luminal area (LA) were measured with this method. In order to determine the structural features of the choroid, using the image binarization method described by Sonoda et al, the choroidal area centered at the fovea 1500 micron wide was binarized with the Niblack thresholding method. Subfoveal choroidal thickness (CT) was measured with the caliper based on the choroidal margins agreed by the two masked ophthalmologists (KME, AE). The area from Bruch's membrane to the choroidoscleral junction was defined as the choroid. Subfoveal total choroidal area (TCA), luminal area (LA), stromal area (SA), and choroidal vascularity index (CVI) were measured using ImageJ software with Niblack binarization method.Ī single 9 mm horizontal EDI OCT line scan (100 frames) image passing through the center of the fovea was used for choroidal imaging. Images were exported in 3 different types: (a) 1:1 pixels, (b) 1:1 micron, and (c) 1:1 micron image screenshot at 400% magnification. According to the OCT beam pupil entry position, 2 different choroidal imaging were performed in the same season: (1)Centered, (2)Nasally-Decentered. Methods: In this study 45 subjects underwent fovea-centered choroidal imaging with EDI mode SD-OCT. The aim of this study is to calculate the CVI without magnification with the M scale of Heidelberg OCT and compare it with the measurements made using the 400% magnified 1:1 micron (x4 M) scale image and P scale image of the same device. In almost all studies on CVI, measurements were made with images provided with P scale. There is no such information about choroidal vascular index (CVI) measurement. It is recommended to measure with M scale in order to avoid erroneous measurements in case the image is tilted in choroidal thickness measurements. Purpose: Heidelberg optical coherence tomography can give images with 1:1 micron (M) and 1:1 pixel (P) scale. Co-authors: Furkan Kirik, Kamile Melis Ertürk, Mehmet Hakan Ozdemir
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