Optical coherence tomography angiography analysis of interocular asymmetry in hydroxychloroquine retinal toxicity

Introduction The purpose of our investigation was to analyze interocular asymmetry of choroidal and retinal microcirculation in patients taking hydroxychloroquine (HCQ) to deepen understanding of the pathogenic mechanism of HCQ retinal toxicity. Methods We conducted a retrospective study. The study included 21 patients using HCQ for over 5 years (high-risk group), 25 patients using HCQ for 5 years or less (low-risk group) and 25 healthy patients. Asymmetry index (AI) of optical coherence tomography angiography (OCTA) quantitative parameters (vessel density (VD) and foveal avascular zone (FAZ) area of superficial capillary plexus (SCP), deep capillary plexus (DCP), total capillary plexus (TCP), and choriocapillaris (CC)) in 4.5 mm × 4.5 mm cube were registered. Results In the HCQ group, AI of CC VD in the central area was decreased compared to the control group, even though statistical significance was not reached ( p value 0.053). In the high-risk group, AI of TCP VD in the foveal region was diminished compared to the low-risk group ( p value 0.021). No differences in AI of SCP and DCP VD and FAZ area were observed between HCQ group and control group, and between high-risk and low-risk groups ( p value >0.05). Conclusion We demonstrated a lower AI of TCP VD in the central area in patients using HCQ for over 5 years. Thus, we suggest that HCQ may play a protective role in preserving ocular microcirculation in patients with autoimmune diseases.