In vivo analysis of choroidal vascularity index changes in eyes with Fuchs uveitis syndrome

• Binarisation of the EDI-OCT images might be a useful technique to differentiate which layers of the choroid affected with the ocular diseases. • In patients with Fuchs uveitis syndrome vitreous condensation and chorioretinal scars are signs of involvement of the posterior segment. • We used new binarisation technique and demonstrated that structural changes in the luminal part of choroid in the affected eyes of these patients. This study aimed to investigate changes in the choroidal vascularity index (CVI) in eyes with Fuchs uveitis syndrome (FUS) and determine the effect of heterochromia on choroidal vascularity using binarisation of enhanced-depth imaging (EDI)-optical coherence tomography (OCT) images. The study included the affected eyes (FEs) and unaffected fellow eyes (NFEs) of 24 patients with unilateral FUS and the eyes of 30 healthy controls (HCs). The subfoveal total choroidal area (TCA) and the luminal area (LA) were determined by binarised EDI-OCT images using Image J software (National Institutes of Health, Bethesda, MD). The CVI value was calculated by dividing the LA value by the TCA value. The CVI values were significantly lower in FEs (58.8 ± 3.7 %) compared to NFEs (62.3 ± 3.9 %, p = 0.002) and HCs (61.1 ± 3.7 %, p = 0.008). The mean LA was significantly narrower in FEs than in NFEs (p = 0.047) and HCs (p = 0.001). Additionally, the mean CVI values were significantly lower in eyes with heterochromia compared to those without heterochromia (p = 0.024) in the affected eyes of patients with FUS. This study shows that there are significant quantitative structural changes, especially in the luminal part of the subfoveal choroid, in eyes with FUS. The choroid seems to be more affected in the presence of heterochromia. These findings might support posterior involvement and the chronicity of the disease.