ABSTRACT
Background Haze formation is a key factor of vision reduce following corneal refractive surgery.Transforming growth factor-β1 (TGF-β1) and α-smooth muscle actin (α-SMA) are documented to participate in haze formation.Laboratory study showed that bevacizumab can not only inhibit corneal neovascularization,but also promote the healing of corneal epithelial basement membrane.However,the impact of bevacizumab on corneal healing after Off-flap epipolis laser in situkeratomileusis (Off-flap Epi-LASIK) is unclear.Objective The present study was to investigate the inhibition effect of bevacizumab on corneal haze after off-flap Epi-LASIK and its active mechanism.Methods Off-flap Epi-LASIK was performed in 24 adult pigmented rabbits and these rabbits were randomized into three groups.Bevacizumab of 0.1 ml (2.5 mg) was subconjunctivally injected 10 minutes after surgery in 16 rabbits and the same amount of bevacizumab was repeatedly injected 4 days after the initial injection in 8 eyes of 16 eyes.In addition,equivalent amount of normal saline solution was used in the same way in the other 8 rabbits.Another 2 health rabbits were used as the blank controls.Operative eyes were examined by slit lamp biomicroscope daily after surgery and haze was scored based on SundarRayde criteria.Corneas were obtained 4 weeks after operation for hematoxylin & eosin and periodic acid Schiff staining.Expressions of TGF-β1 and α-SMA in corneal tissue were detected by immunochemistry.Results Corneal epithelium healed completely in all eyes 4-5 days after operation.The haze scores were lower in the bevacizumab single injection group and repeat injection group than those in the normal saline solution group (P＜0.05) in 1 week and 4 weeks after operation.However,no significant difference was seen in the haze scores between the bevacizumab single injection group and repeat injection group (P ＞ 0.05).The hostopathological examination showed that the fibrosis response of cornea tissue was slight in the bevacizumab single injection group and repeat injection group comparison with the normal saline solution group.At 1 week after operation,the expression levels of TGF-β1 were (49.8 ± 2.1) PU and (38.6 ±4.4) PU in the bevacizumab single injection group and repeat injection group,and those of 4 weeks were (37.7 ±4.8) PU and (28.3 ± 3.5) PU,indicating significant decrease in the TGF-β1 expression compared with (65.1 ±5.3) PU and (51.6±2.2) PU of the normal saline solution group in both 1 week and 4 weeks (P＜0.01).The expression levels of α-SMA in corneas were (67.2±10.0) PU and (32.7±3.1) PU at 1 week,and (34.2±5.7) PU and (22.8±3.0) PU at4 weeks after operation in the bevacizumab single injection group and repeat injection group,which were significantly lower than (87.8±7.7) PU and (59.4±5.6) PU in the normal saline solution group in both 1 week and 4 weeks (P＜0.05).Meanwhile,the expression levels of TGF-β1 and α-SMA were declined in the bevacizumab repeat injection group compared with single injection group (P＜0.01).Periodic acid Schiff staining exhibited that the basement membrane of cornea was intact and continued in bevacizumab injection group.But corneal basement membrane was discontinuous in the normal saline solution group.Conclusions Subconjunctival injection of bevacizumab downregulates the expressions of TGF-β1and α-SMA in cornea after Off-flap Epi-LASIK and thus prevents haze formation.