Association between choroidal vascularity index and disease activity in Behçet uveitis using BOS24 and FFA scores

To compare the choroidal vascularity index (CVI) between eyes with Behçet uveitis and healthy control eyes and to evaluate its relationship with clinical and angiographic disease activity.

This retrospective cross-sectional study included 66 eyes of 36 patients with Behçet uveitis and 60 eyes of 30 healthy participants evaluated between April 2022 and April 2024. CVI was calculated from total choroidal and luminal area measurements obtained from three 9-mm horizontal enhanced-depth imaging optical coherence tomography scans. Clinical activity was assessed using the Behçet's Disease Ocular Attack Score 24 (BOS24), a 24-point composite score incorporating anterior chamber cells, vitreous haze, and newly developed posterior-segment inflammatory lesions. Angiographic activity was assessed using a modified Angiography Scoring for Uveitis Working Group system based on fundus fluorescein angiography (FFA) findings. Generalized estimating equations were used to account for inter-eye correlation.

Mean CVI was significantly lower in eyes with Behçet uveitis than in healthy control eyes (p = 0.001), despite comparable central macular and subfoveal choroidal thickness. BOS24-active eyes had significantly lower CVI and luminal area values than BOS24-inactive eyes (p ≤ 0.005). Although CVI values tended to be lower in FFA-active eyes, most differences were not statistically significant. The lowest CVI values were observed in eyes with concurrent clinical and angiographic activity (FFA+/BOS24+). BOS24-defined peripheral new lesions were the only variable independently associated with lower mean CVI (β = -0.162, p = 0.024).

CVI was lower in Behçet uveitis despite comparable choroidal thickness, indicating alterations in choroidal luminal-stromal composition that were not reflected by thickness measurements alone. Its relationship with BOS24-defined clinical activity was more evident than that with FFA-defined activity. The observed CVI pattern may reflect the combined effects of current inflammation and cumulative vascular remodeling. These findings position CVI as a promising noninvasive structural biomarker that may complement conventional clinical and angiographic assessments of choroidal involvement in Behçet uveitis.