Involvement of Oxidative Stress-Related Inflammatory Mediators in the Pathogenesis and Treatment Response of Macular Edema Secondary to Branch Retinal Vein Occlusion

Background: Branch retinal vein occlusion (BRVO) represents a segmental retinal ischemic disorder characterized by localized oxidative–inflammatory activation. While redox-driven cytokine responses have been described in central retinal vein occlusion, their role in BRVO-specific macular edema and treatment responsiveness remains unclear. This study investigated whether novel redox-related inflammatory mediators in the aqueous humor are associated with disease severity and structural response to anti-vascular endothelial growth factor (VEGF) therapy in BRVO. Methods: Aqueous humor samples were collected from 30 treatment-naïve patients with BRVO and 19 control patients. Levels of VEGF and the novel redox-related inflammatory factors FMS-related tyrosine kinase 3 ligand (Flt-3L), fractalkine, CXCL-16, and endocan-1 were measured by suspension array, and the severity of macular edema was evaluated by measuring central macular thickness and neurosensory retinal thickness (TNeuro) by spectral-domain optical coherence tomography. Therapeutic response was assessed one month after intravitreal ranibizumab injection (IRI). Results: Aqueous levels of VEGF, Flt-3L, and endocan-1 were significantly higher in the BRVO group, and levels of Flt-3L, CXCL-16, and endocan-1—markers associated with oxidative endothelial damage and leukocyte recruitment—correlated significantly with each other and with aqueous flare values. Notably, baseline Flt-3L levels significantly correlated with the reduction in TNeuro, suggesting that this redox-sensitive signaling molecule is a potential biomarker for treatment sensitivity. Conclusions: These findings suggest that novel inflammatory factors, potentially driven by oxidative-nitrosative stress, play a pivotal role in the pathophysiology of BRVO. Baseline Flt-3L may serve as a predictive biomarker for structural responsiveness to anti-VEGF therapy in BRVO, suggesting that oxidative–inflammatory signaling contributes not only to disease severity but also to therapeutic heterogeneity.