| Objective We trickled the amniotic extraction on the ocular surface of the rabbit corneas after the excimer laser photorefractive keratectomy in order to discuss the effect and mechanism of the amniotic extraction on the healing of the corneal wound and explore a new way to reduce the haze after PRK.Method Eighteen New Zealand healthy white rabbits without any ocular disease were divided into three groups randomly, Each group had 6 rabbits,12 eyes. And then they were undergone PRK in the same way using the fifth multiscan exciser laser therapeutic apparantus. After removing corneal epithelium in PTK mode, a wound 6.5 mm in diameter with a depth of 150μm was created in the centre of the cornea in PRK healing mode. All eyes were allocated randomly to be treated with amniotic extraction, or 0.1% dexamethasone as negative control, or steroid as blank control. Each eye's general condition was observed postoperatively every day. The rabbits were killed respectively at 1,4 and 8 weeks postoperatively. Both corneas of each rabbits were removed immediately for H&E staining and undergone examination by light microscopy. Corneal stroma cell apoptosis was evaluated by terminal deoxyribonucleotidy transferase-mediated deoxynuridine triphophate nick end labeling (TUNEL) assay. Myofibroblast genaration were evaluated by immunofluorescence checking the expression ofαlpha-smooth muscle actin(α-SMA). Inflammatory positive cells were evaluated by immunofluorescence checking the expression of CD11b. The number of TUNEL andα-SMA positive cells were semi quantitatively analyzed to explore their effects on corneal haze.Result 1,In three groups, multi-layered neonatal corneal epithelial cell was completely covered the laser section within 4-6 day and the expertimental group grew faster than the other two groups. Epithelial cells of several sizes appeared in the basal lamina. At the 4th week, corneal epithelial cell covering the laser section in both groups. Much neoformative collagen arranged irregularly and cicatricial tissue in the anterior stromal layer. At the 8 week postoperatively, three groups still have not restored the normal thichness of corneal epithelial cell; but in the blank control group there was more neoformative irregular collagen in the anterior stromal layer. More scar can be observed.2,There were no significant inflammatory positive cells in 1,4,8 weeks in all three groups.3,1 week after surgery the TUNEL-positive cells can be observed in all three groups by immunofluorescence staining in stroma, and the experimental group has much less positive cells than the other two groups. 4 week after surgery the TUNEL-positive cells can be observed in bank control, and the experimental group and negative control group has no significant positive cells(p<0.01). There were no significant positive cells in 8 weeks in all three groups.4,1 week, 4 weeks and 8 weeks after surgery the number of myofibroblast cell can be observed by immunofluorescence staining in stroma in negative control and blank control. And the blank control has much more than the negative control. But there were no significant positive cells in experimental group in each three weeks after surgery(p<0.01).Conclusion Our results suggested that amniotic extractraction can reduce the formation of haze. It might release certain factor which transported into corneal matrix, then affected the healing of epithelial cell by enteracting with the corneal cell factor, reduce the cell apoptosis, corneal wound healing response and rebuilt the corneal matrix with less myofibroblast, collagen and less scar.
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