Diabetic macular edema (DME) remains a leading cause of vision impairment among adults with diabetes worldwide. Although current therapies such as anti-VEGF injections and laser treatment provide clinical benefit, the optimal approach to simultaneously target macular structure, visual function, retinal perfusion, and inflammatory activity remains uncertain.

To evaluate the efficacy of Conbercept Plus Dexamethasone compared with Conbercept alone therapy in patients with DME over a 12-month follow-up period.

Forty-six eyes from 46 patients with DME were enrolled in a prospective controlled trial and assigned to an observation group (n = 23, receiving Conbercept Plus Dexamethasone) or a control group (n = 23, Conbercept alone treatment). Central macular thickness (CMT), best-corrected visual acuity (BCVA, LogMAR), superficial vascular density (SVD), deep vascular density (DVD) were measured at baseline and at 1, 3, 6, and 12 months post-treatment. At baseline and 3 months after the fourth vitreous cavity injection, levels of interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), and vascular endothelial growth factor (VEGF) were measured in the aqueous humor. Repeated measures ANOVA and correlation analyses were performed.

At baseline and during the first three months, CMT and BCVA did not differ between groups. At 6 and 12 months, the observation group had significantly lower CMT (236.09 ± 21.94 μm and 239.61 ± 28.77 μm) than controls (343.83 ± 60.23 μm and 322.70 ± 56.19 μm; both p < 0.001), with BCVA showing a trend toward improvement at 6 months (p = 0.060) and significant gain at 12 months (p = 0.001). DVD increased significantly in the observation group at 6 and 12 months (p = 0.018 and 0.045), while SVD remained similar. Inflammatory cytokines decreased in both groups, but reductions in IL-6, IL-8, IL-10, and VEGF were greater in the observation group (all p < 0.05). CMT strongly correlated with BCVA (r = 0.778, p < 0.001), and weak but significant correlations existed between glycemic indices and retinal parameters.

Conbercept Plus Dexamethasone provides superior long-term structural, functional, and microvascular benefits compared with conventional therapy, likely mediated by enhanced resolution of inflammation. CMT strongly predicts visual outcomes, supporting its use as a primary surrogate marker in clinical management of DME.