Choroidal vascularity index in hydroxychloroquine toxic retinopathy

Purpose: To investigate choroidal involvement in eyes of patients treated with hydroxychloroquine (HCQ), by quantifying the choroidal vascularity index (CVI) and other choroidal biomarkers. Methods: Vertical enhanced depth imaging spectral domain optical coherence tomography (SD-OCT) scans were performed in eyes with either advanced-stage or mild HCQ toxic retinopathy, as well as in healthy age-matched and sex-matched controls. Based on SD-OCT scans, the subfoveal and mean choroidal thickness (ChT) was measured. The CVI, total choroidal area (TCA), luminal choroidal area (LCA), and stromal choroidal area (SCA) were calculated based on a binarization image process. These variables were computed and compared between the three groups (i.e., advanced stage, mild toxicity, and healthy controls). Results: Forty-eight eyes of 47 patients under HCQ (26 eyes presented with advanced stage HCQ toxicity and 22 eyes with mild toxicity) and 34 eyes of 31 healthy controls were included. Both CVI and ChT were significantly different between the three groups ( P < 0.001, P < 0.001). When comparing the advanced stage toxicity group to healthy controls, both the subfoveal and the mean ChT were diminished ( P < 0.001). The CVI, TCA, LCA, and SCA were significantly lower in the advanced stage of toxicity group when compared with controls ( P < 0.001, <0.00001, <0.0001, and P = 0.0094, respectively). Conclusion: Our study suggests that eyes with HCQ toxic retinopathy, especially at advanced stages, present with choroidal impairment, giving further pathophysiological insights into the unfolding of this retinal toxicity.