ABSTRACT
Background Researches demonstrated that avastin-assisted vitrectomy for serious proliferative diabetic retinopathy can decrease intra-operation complication and bring down difficulty of surgery.It is speculated that this is associated with suppression of avastin on neovascularization.However,the evidence of its pathology is lack.Objective The aim of this study was to evaluate the application and mechanism of avastin in vitrectomy for severe proliferative diabetic retinopathy. Methods Twenty-four eyes from consecutive 24 patients with vitrectomy for severe proliferative diabetic retinopathy were enrolled in this study.Fourteen eyes received all intravitreal injection of 0.06 ml avastin(1.5 mg)14 days prior to vitrectomy。And the other 10 eyes underwent only vitrectomy without avastin injection as controls,Preretinal membranes were collected during vitrectomy for histopathologic examination by hemotoxylin and eosin staining.The differences in the density of the neovessels and micro-neovessels between the two groups were observed by detecting the expression of CD34 in vesse]endothelial cells using immunohistochemistry.Written informed consent was obtained from each patient before surgery. Results No statistically significant differences were found in the demography and eye manifestations between only vitreetomy group and avastin+vitrectomy group(P＞0.05).The neovessels with grade three was in 10 eyes in only vitrectomy group and 1 eye in avastin+vitrectomy group(P＜0.01).More capillary-like neovascularization with single vascular endothelial cells,obvious hemorrhage and inflammatory cells infiltration were observed on preretinal membranes in vitrectomy group.However,there were less hemorrhage,ceUular components and few capillary-like neovascularization but more hyaline degeneration of fibrous tissue were observed in avastin+vitrectomy group under the light microscope.Immunochemistry revealed that CD34 was positively expressed in vascular endothelial cells on preretinal membrane in both two groups.The neovessels density and miero-neovessels density were 15.40±7.42/field and 1.88±1.70/field in avastin+vitrectomy group and those in vitreetomy group were 18.00±3.80/field and 0.45±0.56/field respectively,showing significant differences between these two groups(neovessels density:Z=-4.102,P＜0.01;micro-neovessels density:Z=-4.137,P＜0.01).Conclusion As an adjunct drug during the vitrectomy for proliferative diabetic retinopathy, avastin can improve the successful rate of surgery by inhibiting the neovascular formation and alleviating retinal edema.