Objective:To study the effect of ranibizumab on retinal oxidative stress in a rat model of choroidal neovascularization (CNV) and its mechanism.Methods:Sixty SPF male SD rats aged 10 weeks were randomly divided into normal control group, model control group, ranibizumab group, nuclear factor erythroid 2-related factor 2 (Nrf2) inhibitor (ML385) group, ranibizumab+ ML385 group, with 12 rats in each group according to a random number table.Except for the normal control group, the CNV model was established in the other four groups via krypton laser induction.According to grouping, the ranibizumab group, ML385 group and ranibizumab+ ML385 group were intravitreally injected with 1 μl of ranibizumab, ML385 and ranibizumab+ ML385, respectively.Model control group and normal control group received an intravitreal injection of normal saline of equal volume.The CNV area was measured through choroidal wholemounts.Pathological change of the retina was observed by hematoxylin and eosin staining.Expressions of Nrf2, superoxide dismutase (SOD) and quinone oxidoreductase 1 (NQO1) were detected using Western blot and real-time PCR.The use and care of animals complied with laboratory animal welfare guidelines.The study protocol was approved by the Laboratory Animal Welfare and Ethics Committee of Tengzhou Central People's Hospital (No.JN.No20210214S1200430[121]).Results:CNV areas of the model control group, ML385 group and ranibizumab+ ML385 group were (23.01±1.52)×10 3, (30.23±2.01)×10 3 and (18.56±1.85)×10 3 μm 2, respectively, which were significantly higher than (12.35±1.22)×10 3 μm 2 of ranibizumab group (all at P<0.001). The CNV area of ranibizumab+ ML385 group was smaller than that of model control group and ML385 group, and the CNV area of ML385 group was larger than that of model control group, showing statistically significant differences (all at P<0.001). Hematoxylin and eosin staining showed that the structural damage of the retinal pigment epithelium-choroid-sclera complex was slighter in ranibizumab group than model control group, severer in ranibizumab+ ML385 group than ranibizumab group but slighter than model control group, severer in ML385 group than model control group.The mRNA and protein expressions of Nrf2, SOD and NQO1 of ranibizumab group were lower than those of normal control group but higher than those of model control group, ML385 group and ranibizumab+ ML385 group, and the differences were statistically significant (all at P<0.05). The mRNA and protein expressions of Nrf2, SOD and NQO1 were higher in ranibizumab+ ML385 group than model control group and ML385 group, showing statistically significant differences (all at P<0.05). Conclusions:Ranibizumab can inhibit the growth of CNV induced by krypton laser and reduce RPE damage caused by retinal oxidative stress.The mechanism is related to the activation of Nrf2/ARE pathway.