Inclusion Criteria:  PDR patients with severe vitreous hemorrhage who cannot collect oct images and need vitrectomy Type 2 diabetes, aged 18~80 years old Good blood sugar control (glycated hemoglobin <8.3%) Sign the informed consent form voluntarily, and are willing and able to follow the outpatient visits and research procedures within the time specified in the trial  Exclusion Criteria:  Exclude severe infections of conjunctiva, cornea, and sclera Combined with other retinal vascular diseases such as retinal vein occlusion Cardiorenal insufficiency Myocardial infarction or stroke occurred within 6 months.