Purpose: To compare vitreous and serum concentrations of interleukin (IL-1β) and interleukin-33 (IL-33) between eyes with proliferative diabetic retinopathy (PDR) and nondiabetic surgical controls, and to explore associations between cytokine levels and clinical characteristics. Methods: Eighty-four eyes of 84 consecutive patients were prospectively enrolled: 42 eyes with PDR undergoing pars plana vitrectomy for vitreous hemorrhage or tractional retinal detachment and 42 nondiabetic controls undergoing vitrectomy for idiopathic epiretinal membrane. Undiluted vitreous and paired venous blood samples were collected perioperatively. IL-1β and IL-33 levels were quantified by ELISA. Results: Both vitreous and serum cytokine levels were significantly higher in PDR than in controls. Median vitreous IL-1β and IL-33 concentrations were 18.85 and 43.76 pg/mL in PDR versus 11.74 and 35.36 pg/mL in controls ( P = 0.003 and P < 0.001). The median serum IL-1β and IL-33 levels were 25.87 and 49.27 pg/mL in PDR compared with 20.73 and 34.09 pg/mL in controls ( P = 0.009 and P < 0.001). Serum concentrations exceeded vitreous levels across groups. Within the PDR cohort, vitreous and serum levels were correlated for IL-1β ( r = 0.51, P < 0.001) and IL-33 ( r = 0.39, P = 0.012). Duration of diabetic retinopathy showed a mild negative correlation with serum IL-1β ( r = −0.32, P = 0.037). Conclusions: PDR is characterized by concomitant intraocular and systemic upregulation of IL-1β and IL-33, with serum levels consistently exceeding vitreous concentrations and showing partial correlation between compartments. These findings support an IL-1–IL-33–associated inflammatory signature that spans both retinal and systemic levels and highlight IL-1β and IL-33 as potential biomarkers or candidate mediators in advanced PDR.
Çelik et al. (2026) studied this question.