Diabetic macular edema (DME) is the main cause of severe vision loss in diabetic retinopathy. Intravitreal injection of anti-vascular endothelial growth factor (VEGF) and Ozurdex are two safe and effective ways to treat DME. Pars plana vitrectomy is mainly suitable for the treatment of unabsorbed vitreous hemorrhage (VH) and tractional retinal detachment caused by proliferative diabetic retinopathy (PDR). Intraoperative optical coherence tomography (OCT), a diagnostic device, can be used to evaluate the potential condition of the retina. Many patients with PDR have unclear refractive stroma due to VH and other reasons, so preoperative OCT cannot give a clear diagnosis, so the use of intraoperative OCT can judge whether the patients are complicated with DME and give corresponding treatment. The purpose of this study is to explore the prognosis of patients with DME diagnosed by OCT during PPV and treated with PPV combined with aflibercept or PPV combined with Ozurdex, and to observe and compare the postoperative anatomical results, functional results, times of reinjections and the occurrence of adverse events between the two groups, in order to provide accurate treatment for patients, reduce the frequency of postoperative vitreous injection and lighten the burden of patients.

Inclusion Criteria:

• ≥18 years of age;
• Patients and their families fully understand the research and must sign an informed consent form;
• Patients have a history of diabetes and were diagnosed with PDR by ophthalmic examination;
• Haemoglobin A1c (HbA1c) levels of <10% within 3 months;
• No contraindication of vitrectomy;
• Pseudophakia or this operation is combined with phacoemulsification and lens implantation;
• Diagnosed with DME by intraoperative optical coherence tomography during vitrectomy

Exclusion Criteria:

• The follow-up period is less than 6 months;
• Patients need gas or silicon oil tamponade;
• Patients with rubeosis iridis, neovascular glaucoma and endophthalmitis;
• Patients with other intraocular surgeries (except cataract surgery with no ruptured posterior lens capsule);
• Patients with other retinal diseases (i.e., age-related macular degeneration, retinal vein occlusion);
• Patients received intravitreal Ozurdex three months prior to screening or anti-VEGF injection one month prior to screening;
• Patients with uncontrolled systemic disease