AIM: To evaluate the relationship between intravitreal bevacizumab(IVB) treatment and the levels of vitreous vascular endothelial growth factor(VEGF), basic fibroblast growth factor(b FGF) and vitreous-retina surface fibrosis in patients with proliferative diabetic retinopathy(PDR).·METHODS: This study was a prospective, open-label,controlled, randomized clinical trial. Sixty-eight eyes of PDR patients(n =53) and macular hole patients(n =15)were enrolled in this study. Thirty-four eyes of the PDR patients received IVB before vitrectomy. Twenty-three of the 34 PDR patients received IVB treatment 5d before vitrectomy(subgroup a), and 11 of the 34 PDR patients received IVB treatment greater than 2wk prior to vitrectomy(subgroup b). Nineteen of the PDR patients did not receive IVB treatment at any time prior to vitrectomy. The levels of b FGF and VEGF in vitreous samples were measured using enzyme-linked immunosorbent assay(ELISA) and the degree of vitreoretinal fibrosis was characterized using clinical data and data obtained intra-operatively.·RESULTS: In PDR patients, VEGF and b FGF levels were significantly increased compared to non-PDR(control) subject’s eyes(P <0.01). In PDR patients,vitreous VEGF levels were significantly decreased following IVB treatment compared to PDR patients that did not receive IVB treatment(P <0.01). The degree of vitreoretinal fibrosis was significantly increased in subgroup b compared to subgroup a(P <0.05) and to patients that did not receive IVB(P <0.05). Vitreous b FGF levels were significantly greater in subgroup b than subgroup a(P <0.01) or in patients who did not receive IVB treatment(P <0.05). A Spearman’s rank correlationtest indicated that higher levels of vitreous b FGF, but not VEGF, correlated with the degree of vitreoretinal fibrosis.·CONCLUSION: We found that b FGF levels increase in PDR patient’s vitreous after IVB treatment longer than two weeks prior to vitrectomy and correlated with the degree of fibrosis after IVB treatment. These findings suggest vitreous fibrosis is increased in PDR patients after IVB treatment may be due to increased levels of b FGF. AIM: To evaluate the relationship between intravitreal bevacizumab (IVB) treatment and the levels of vitreous vascular endothelial growth factor (VEGF), basic fibroblast growth factor (b FGF) and vitreous-retina surface fibrosis in patients with proliferative diabetic retinopathy (PDR). · METHODS: This study was a prospective, open-label, controlled, randomized clinical trial. Sixty-eight eyes of PDR patients (n = 53) and macular hole patients (n = 15) were enrolled in this study. of the PDR patients received IVB before vitrectomy. Twenty-three of the 34 PDR patients received IVB treatment 5d before vitrectomy (subgroup a), and 11 of the 34 PDR patients received IVB treatment more than 2 weeks prior to vitrectomy of the PDR patients did not receive IVB treatment at any time prior to vitrectomy. The levels of b FGF and VEGF in vitreous samples were measured using enzyme-linked immunosorbent assay (ELISA) and the degree of vitreoretinal fibrosis was RESULTS: In PDR patients, VEGF and b FGF levels were significantly increased compared to non-PDR (control) subjects’ eyes (P <0.01). In PDR patients, vitreous VEGF levels were significantly decreased of IVB treatment compared to PDR patients that did not receive IVB treatment (P <0.01). The degree of vitreoretinal fibrosis was significantly increased in subgroup b compared to subgroup a (P <0.05) and to patients that did not receive IVB (P <0.05). Vitreous b FGF levels were significantly greater in subgroup b than subgroup a (P <0.01) or in patients who did not receive IVB treatment (P <0.05). A Spearman’s rank correlation test indicates that higher levels of vitreous b FGF, but not VEGF, correlated with the degree of vitreoretinal fibrosis. CONCLUSION: We found that b FGF levels increase in PDR patient’s vitreous after IVB treatment longer than two weeks prior to vitrectomy and correlated with the degree of fibrosis after IVB t reaThese findings suggest that vitreous fibrosis is increased in PDR patients after IVB treatment may due due to increased levels of b FGF.