| Objective We stitched 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 membrane on the healing of the corneal wound,the quality of tear-film and explore a new way to reduce the haze and dry eye after PRK.Method Eighteen New Zealand healthy white rabbits without any ocular disease were undergong PRK in the same way using the fifth multiscan exciser laser therapeutic apparantus,18 rabbits,36 eyes in all. 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 control, or steroid as blank.Each group had 6 rabbits,12 eyes.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 and undergone examination by light microscopy,meanwhile the thickness of proliferative epithelial cell in the centre of cornea was measured and analyzed statistically.Haze of all rabbits was observed by slit lamp microscopy ,recorded by photo slit lamp syste and evaluated according to Fantes Grade at 1th,4th and 8th postoperatively.These morphological changes were histopathologically analysed using dichlortriazinyl aminofluorescein.Meanwhile tear film was observed.Result During the early postoperative stage,the result of fluorescent staining was positive in all eyes.In three groups,multi-layered neonatal corneal epithelial cell was completely covered the laser section within 4-6 day,which of the expertimental group grew faster than the other groups;epithilial cells of several sizes appeared in the basal lamina.There was no difference among the three groups.At the 4th week,corneal epithelial cell covering the laser section in both groups was much neoformative collagen arranging 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 group there was more neoformative irregular collagen in the anterior stromal layer.More scar can be observed. In the center of the laser section,the thickness of epithelial cell in the experimental group was significantly less than that in and control group and blank.(p<0.05).Not only the result of impression cytological,but the number of caliciform cell acquired by ferning test,there were more significant deviation in experimental group than the blank. at 4 and 8 weeks postoperatively,and more significant than control at 4 weeks postoperatively(p<0.05).Although different levels of haze had appeared since one week postoperatively, predominant at 4 week postoperatively,the degree of it was singnificantly lower in the experimental group than the control and blank.There was no statistical difference between experimental group and control group(p<0.05).Conclusion Our results suggested that PRK combined amniotic extractraction was safe and effective.It was able to reduce corneal wound healing response and formation of postoperative haze.Amniotic membrane matrix might release certain factor which transported into corneal matrix,then affected the healing of epithelial cell by enteracting with the corneal cell factor,and rebuilt the corneal matrix with less collagen and less scar by interaction between epithelial and matrix.Meanwhile,the amniotic extractraction plays an active part in the recovery of the appearance and function of tear-film. |
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