The goal of this clinical trial is to learn if the efficacy of dexamethasone implant combined with anti-VEGF superior to anti-VEGF monotherapy in the treatment of DME in Chinese patients. The main questions it aims to answer are:

1. Whether combination therapy improves the best corrected visual acuity at 6 months and 12 months?
2. Does combination therapy improve retinal anatomy better than monotherapy at each time point?

Researchers will compare the combination therapy to the monotherapy to see if dexamethasone implant combined with anti-VEGF will leads to better results.

Participants will:

1. be randomly assigned to one of two groups with equal probability to receive the combination of intravitreal anti-VEGF and dexamethasone implant injections or intravitreal anti-VEGF injections.
2. During the first 3 months, patients in both groups will receive monthly injections of anti-VEGF. In the double protocol group, the first dexamethasone implant injection will be administered simultaneously with the first loading dose of anti-VEGF injections. Between 4 and 12 months, patients will receive intravitreal anti-VEGF injections as needed/pro-re-nata (PRN).
3. Patients will have regular follow-up. Routine examination includes Central retinal thickness (CRT), intraocular pressure (IOP), slit lamp examination, best corrected visual acuity (BCVA) and OCT.

Inclusion Criteria:

• Type 1/type 2 diabetes mellitus with good glycaemic control and glycated haemoglobin ≤ 10.0%; DR stage II-III;
• DME with involvement of the central concavity and resulting in the patient's vision loss;
• Central retinal thickness (CRT) ≥250 μm;
• No refractive interval clouding and pupillary constriction affecting fundus examination;
• No Pan-Retinal Photocoagulation treatment within 3 months before enrolment;
• No macular laser treatment in the past or during the follow-up period;
• Good patient cooperation and compliance.

Exclusion Criteria:

• other macular lesions such as macular preexisting membranes, macular schisis, or other causes of macular oedema such as uveitis and central retinal vein occlusion;
• Co-existence of diabetic optic neuropathy;
• Previous intraocular injection therapy such as anti-VEGF drugs or glucocorticoid drugs in the target eye;
• History of vitreoretinal surgery in the target eye;
• A history of uncontrolled stable glaucoma or hypertension, hormonal hypertension in the target eye;
• Aphakic eyes with posterior lens capsule rupture with an anterior chamber IOL (ACIOL), iris or transscleral fixed intraocular IOLs, and patients with posterior lens capsule rupture;
• Pregnant or breastfeeding patients, uncontrolled hypertension within 3 months, cerebrovascular accident or myocardial infarction, uncontrolled diabetes mellitus, or other reasons for not being able to co-operate with the relevant examination;
• Lost visits and data loss.

demographic data, diagnostic results, treatment data, lab test results, follow-up data Etc.