·AIM:To evaluate the efficacy of Avastin on treating the bleb fibrosis after trabeculectomy in rabbits.·METHODS:Forty eyes of 20 rabbits undergone trabeculectomy were randomly divided into three different doses of Avastin experimental groups,mitomycin C(MMC)group and blank control group.The eyes in three Avastin experimental groups were randomly received subconjunctival injection of 0.5,1,2mg Avastin when trabeculectomy finished and on 3rd,7th days after surgery.In the MMC treated group,MMC cotton patch,0.2g/L,was put under the capsule Tenons and scleral flap during operation.The appearance of filtrating bleb and inflammatory reactions were observed under slit-lamp;the filter areas were taken histopathologic examination on postoperative 7,14 days.·RESULTS:Filter blebs could be seen clearly in each group on postoperative 7 days.And on postoperative 14 days in the 2mg Avastin group and MMC group,filtering blebs were larger and more elevated than other groups;in 1mg Avastin group,there were only some small blebs;and in 0.5mg Avastin group and blank control group,filter blebs disappeared,and marked hyperplasia of fibrous tissue could be seen.Under the microscope on postoperative 7 days,there was no significant difference in the percentage of the bleb cavity surface area in the conjunctiva and the percentage of bleb-forming region in the conjunctiva.On postoperative 14 days,the percentage of the bleb cavity surface area in the conjunctiva of 2 mg and 1mg Avastin groups and MMC group were respectively 1.0%,0.8%,0.9%;and the percentage of bleb-forming region in the conjunctiva were 26.1%,2.9%,25.8%.The percentage of the bleb cavity surface area in the conjunctiva and the percentage of bleb-forming region in the conjunctiva of 2mg and 1 mg Avastin group were significantly higher than the blank control group,respectively(P=0.00;P=0.00).But there was no significantly difference between 2mg Avastin group and MMC group on the filtering bleb area percentage.·CONCLUSION:Subconjunctival injection of Avastin can effectively prevent the bleb fibrosis,maintain larger bleb area.This indicates that Avastin is most likely to be a novel agent to prevent excessive scarring following trabeculectomy.·