| Objective To observe the pathologic changes in rat cornea after cautery with acid, discuss the correlation between the infiltrating of leucocytes and the epithelial defect, the corneal neovascularization (CNV), and to investigate whether oxidative damage occurs during cornea acid burn.Methods The model of mild, moderate and severe acid burn in the cornea of healthy Long-evans rat was established with 1mol/L sulfuric acid. Corneal angiogenesis and the epithelium deficiency were observed with a slit lamp microscope and the eye photos were taken with a digital camera immediately after cautery with acid, and on day 1 , 3, 7, 14, 21 , 28. The ratio of neovascularization area to that of cornea was calculated. The histopathological changes in rat cornea were observed by hematoxylin and eosin(HE) staining technique, trypan blue and alizarin red S staining technique, and the ultrastructural changes were observed by transmission electron microscope (TEM). The number of leucocytes was calculated, the contents of SOD and MDA in cornea were detected and the result was analyzed statistically using Pearson correlation.Results1. In mild acid-burn, only epithelial damage could be seen in cornea. The speed of corneal wound healing was fast; the cornea was transparent, and no CNV could be seen. Only a few of leucocytes could be seen in corneal limbus. Compared to normal cornea ,there was no statistical difference of MDA and SOD in mildly-burned cornea.2. In moderate acid-burn cornea, the damage could be seen both in corneal epithelium and stroma, and it took more time for corneal wound to heal. Thin nebula and a little of CNV left after corneal wound healing. More leucocytes infiltrated and more fibroblast arised in stroma during the period of repairing. The content of MDA increased slightly, and the vigor of SOD decreased transiently, then increased compensatedly.3. In severe acid-burn cornea, All layers of cornea were damaged. The epithelium andstroma often shed and the cornea became thinner. It took much more time for corneal wound to heal. Ulcer focus could be seen in cornea, and several corneal perforation occurred. Heavy opacity and a lot of CNV presented. Necrosis and shedding in endothelial cells could be seen in the wound area. During corneal repairing, the endothelial cells enlarged, deformed and migrated from peripheral area, which was not damaged, to the wound area and covered it. Sometimes several layers of endothelial cells could be seen. A great number of leucocytes infiltrated in cornea and a lot of fibroblast arised in stroma. The content of MDA increased, and the vigor of SOD decreased. There was significant negative correlation between the changes of MDA and SOD(r=-0.7926, P<0.01). The content of MDA got to the peak while the vigor of SOD decreased to rock bottom on day 7 after severe acid-burn, and the cornea melted most seriously at that time.4. The epithelium deficiency and CNV were positively correlated with the infiltrating leucocytes (r=0.7296, PO.01; r=0.1779, PO.05) and the content of MDA(r=0.6277, P<0.01; r=0.6056, P<0.01); and negatively correlated with the vigor of SOD(r=-0.7082, P<0.01;r=-0.3168, PO.01).Conclusion1. The direct damage of acid burn depended on the concentration of acid and the time that the acid contacted with cornea. Along with the contacted time prolonging, the whole layers of cornea could be damaged severely while the concentration of acid kept constant.2. Leucocytes infiltrated in cornea after acid burn, and the number of leucocytes was correlated with the degree of acid-burn positively. The infiltrating leucocytes could delay the healing of corneal epithelium and promoted the CNV.3. Oxidative damage took part in the secondary lesion after severe acid burn, and it correlated with the corneal melting, the epithelial deficiency and the CNV.
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