Longitudinal Alterations of Retinal and Choroidal Structure in Patients Recovered from COVID-19

Figure 1

Choroidal vascular index (CVI). The first column (a–c) shows the baseline visit of a patient. The second (d–f) and third (g–i) columns relate to the same person in the first and third visits. To calculate CVI, the image was converted to 8 bits and the brightness was set at the measure of the average of three 9-micron lumens of blood vessels. Corneoscleral junction was determined. The image was binarized using Niblack auto local threshold (the middle rows). The area was added to the ROI tool. Then, the image was converted to the RGB, and the color threshold tool was used for thresholding the image. The area was added to ROI; another time was with the AND tool. The selected area was measured as the luminal area (LA). In the last rows between the yellow areas, the grey zones represent the LA and the bright zones demonstrate the stromal area. The CVI was calculated by dividing LA by the total choroidal area.

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