Patients were randomized into three groups according to the random number table: vitrectomy group, vitrectomy + panretinal photocoagulation group and panretinal photocoagulation group alone. 1. Vitrectomy group: vitrectomy was performed for severe non-proliferative diabetic retinopathy, but retinal laser photocoagulation was not performed. 2. Vitrectomy + panretinal photocoagulation group: vitrectomy was performed for severe non-proliferative diabetic retinopathy, and retinal laser photocoagulation was performed during the operation. 3. panretinal photocoagulation group: only retinal laser photocoagulation treatment was performed for severe non-proliferative diabetic retinopathy. All patients were regularly reviewed after surgery (preoperative, 1 week, 1 month, 3 months, 6 months, 12 months, 24 months, and the time and frequency of follow-up were increased according to the specific condition recovery), and the same physician assessed the retinal restoration and visual acuity recovery, and the follow-up time was not less than 12 months. The main outcome measures included the incidence of PDR, such as vitreous hemorrhage, the presence of neovascularization, fibroproliferative membranes, or traction retinal detachment. Secondary study endpoints included: (1) optimal corrected visual acuity; (2) Changes in the thickness of each retina layer; (3) Visual field changes; (4) area of retina without perfusion; (5) retinal neovascularization area; (6) the epiretinal membrane; (7) Low intraocular pressure/increased intraocular pressure, iris neovascularization and lens opacity, etc.
To investigate the prognosis of retinal structure and function after vitrectomy in patients with severe non-proliferative diabetic retinopathy, to explore the feasibility of vitrectomy in patients with severe non-proliferative diabetic retinopathy(NPDR), and to seek the best way to delay the progression of diabetic retinopathy from the perspective of therapeutic effect.