Objective To compare the outcomes of ranibizumab and conbercept adjunct for pars plana vitrectomy (PPV) in the treatment of proliferative diabetic retinopathy (PDR). MethodsA prospective randomized case-control study. From June 2022 to December 2023, 90 cases (90 eyes) of PDR patients diagnosed through ophthalmic examination at Department of Ophthalmology of Gansu Provincial Hospital were included in the study. All patients underwent the best corrected visual acuity (BCVA), intraocular pressure, B-mode ultrasound, and optical coherence tomography (OCT) examinations. The macular foveal retinal thickness (MFRT) was measured using an OCT instrument. The patients were randomly divided into a intravitreal injection of ranibizumab group (monoclonal-antibody group) and a intravitreal injection of conbercept group (fusion-protein group) using a random number table method, with 45 cases (45 eyes) in each group. Two groups of patients were intravitreal injected with 10 mg/ml ranibizumab or conbercept 0.05 ml, respectively. A standard 23G PPV was performed through the flat part of the ciliary body 3-7 days after intravitreal injection. Relevant examinations were performed using the same equipments and methods as before surgery at postoperative 1 week, 1, 3, 6, and 12 months. The PPV time, intraoperative use of intraocular electrocoagulation, incidence of iatrogenic retinal breaks, and sterile air or silicone oil tamponade rate in the vitreous cavity, the postoperative changes of BCVA and MFRT, and incidence of complications were compared between two groups. Independent sample t test was used for inter group comparison. ResultsThe intraoperative utilization rate of intraocular electrocoagulation in the monoclonal-antibody group was higher than that in the fusion-protein group, and the difference was statistically significant (χ2=3.876, P＜0.05). There were no statistically significant differences in the PPV time (t=0.152), intraoperative bleeding rate (χ2=0.800), incidence of iatrogenic retinal breaks (χ2=1.975), and sterile air and silicone oil tamponade rate in the vitreous cavity (χ2=1.607, 1.553) between the two groups (P＞0.05). There were no statistically significant differences in early and late postoperative vitreous hemorrhage (χ2=1.235, 2.355), and re-PPV (χ2=2.355) between two groups (P＞0.05). The BCVA of the fusion-protein group was significantly better than that of the monoclonal-antibody group at postoperative 3 months, and the difference was statistically significant (t=2.428, P＜0.05). The MFRT of the fusion-protein group was lower than that in the monoclonal-antibody group at postoperative 1 week, and the difference was statistically significant (t=2.739, P＜0.05). None of the patients experienced endophthalmitis, retinal artery occlusion, or severe cardiovascular events after surgery. ConclusionCompared with intravitreal injection of ranibizumab before PPV, intravitreal injection of conbercept before PPV in PDR patients can shorten the surgical time, reduce intraoperative bleeding rate, lower the rate of electrocoagulation and intraocular tamponade, and incidence of iatrogenic retinal breaks, and improve the visual acuity.