Panretinal photocoagulation (PRP) has been the standard treatment for Proliferative diabetic retinopathy (PDR) since the Diabetic Retinopathy Study demonstrated its benefit nearly 40 years ago,but PRP has inevitable adverse effects on visual function. Intravitreal injection of vascular endothelial growth factor(VEGF) can induce short-term regression of retinal neovascularization(NV). The purpose is to assess and compare the efficacy and safety between intravitreal injection of conbercept and PRP.

Proliferative diabetic retinopathy (PDR) is a leading cause of vision loss in patients with diabetes mellitus,which of the initial manifestation of PDR is retinal neovascularization at the disc or elsewhere.Panretinal photocoagulation (PRP) has been the standard treatment for PDR since the Diabetic Retinopathy Study demonstrated its benefit nearly 40 years ago,but PRP has inevitable adverse effects on visual function including peripheral visual field defects, night vision loss, loss of contrast sensitivity.Recent evidences have indicated that anti-vascular endothelial growth factor(VEGF) treatment can reduce the severity and delay the progression of DR.However,the impact of this treatment on visual function and the effect of anti-VEGF agents on retinal neovascularization compared with PRP remain unclear. It is possible that a long-acting anti-VEGF agent such as conbercept. So we design the study with is a prospective randomized controlled trial about Intravitreal injection of conbercept versus PRP on PDR.Primary outcome is the change in BCVA from screening to 12 months in the study eye measured in the ETDRS letter score at 4 m

Inclusion Criteria:

1. Participants of either sex aged 18 years or over.
2. Diagnosis of diabetes mellitus (type 1 or 2).
3. Best-corrected visual acuity (BCVA) in the study eye better than or equal to 30 Early Treatment Diabetic Retinopathy Study (ETDRS) letters
4. PDR with no evidence of previous PRP.
5. Media clarity, pupillary dilation and participant cooperation sufficient for adequate fundus photographs.

Exclusion Criteria:

1. a glycated haemoglobin (HbA1c) level of more than 10%;
2. Blood pressure > 180/100 mmHg
3. Myocardial infarction, other acute cardiac event requiring hospitalization, stroke, transient ischemic attack, or treatment for acute congestive heart failure within 6 months
4. dialysis or renal transplant
5. Systemic anti-VEGF or pro-VEGF treatment within 6 months prior to randomization
6. For women of child-bearing potential: pregnant or lactating or intending to become pregnant within the next 3 years
7. Traction retinal detachment involving the macula
8. Exam evidence of neovascularization of the angle
9. History of major ocular surgery or anticipated within the next 6 months following randomization