The study was approved by the Human Research Committee of the Kyoto Prefectural University of Medicine, Kyoto, Japan. Vitreous fluid was obtained from 49 eyes of 48 patients with PDR (49 specimens) at the time of therapeutic vitrectomy, and 19 patients who underwent nondiabetic vitrectomies (19 specimens) served as controls. The specimens were collected with proper informed consent. The diabetic subjects comprised 20 men and 28 women whose mean (±SD) age was 54.3 (±11.9) years. The duration from the initial diagnosis of diabetes mellitus to surgical procedure varied from 0.3 to 30 years, with a mean of 12.4 years. The glycosylated hemoglobin value, measured within 1 month of the operation, was 0.08±0.02% (7.7±1.9%). Of these 48 patients, 27 (28 specimens) had been receiving insulin treatment as their glycemic management, and 21 (21 specimens) had not. Of the 49 specimens, 21 had TRD combined with VH, 19 had TRD without VH, 6 had VH without TRD, and 3 had neither VH nor TRD. Of these PDR specimens, 5 patients had rubeotic glaucoma, and 9 had "burned-out" retinopathy, whose neovascular activity is inactive. The 19 control subjects comprised 8 men and 11 women, whose mean (±SD) age was 60.2 (±12.3) years; 9 had an idiopathic macular hole, 6 had retinal detachment due to a macular hole, and 4 had rhegmatogenous retinal detachment. No proliferative changes were found in the retinal detachments. Table 1 details the patients in the group with PDR and the control group.