A Comparative Study Of Off-flap Epi-LASIK And PRK By The Pathology Effect Of Rabbit Cornea

Objective :To investigate the pathological effects of off-flap Epi- LASIK versus PRK on corneas of rabbits.Method :Newzealand rabbits were used in the experiment. Epi-polis laser in-situ keratomileusis (Epi- LASIK ) was used on right eyes of 32 rabbits and the left eyes of them were photorefractive keratectomized(PRK). Vehicle control eyes were 4 intact eyes of 2 rabbits. 4h,1d, 3 d, 5 d, 7 d, 14d, 1m, 3m after operation,corneas were caught for make specimens. HE staining was used to observe the the variety of the anterior corneal stroma cells. PCNA were stained by means of immunohistochemistry to see the proliferation of the corneal limbus epithelium cells. The proliferation of the central corneal keratocytes was observed by Ki-67.α-SMA was used to research the transformation of the central corneal keratocytes to myofibroblasts and the ultrastructural changes of cornea were observed by transmission electron microscope. We counted these numbers and semiquantitatively analyzed the datas from the effect factors of the formation of haze.Results:The number of anterior corneal stroma cells significantly reduced after PRK or Epi-LASIK and the lowest number was observed 1d after the operation(p<0.01). Compared with the Epi-LASIK group, the number of anterior corneal stroma cells of PRK group on each time stage after the operation was significantly lower(p<0.01). In two groups, the PCNA highly expressed after operation and the highest level were observed 3d after opration , 1m later, it came to normal(p<0.05). The number of PCNA positive cells in PRK group were more than the Epi-LASIK group 1d, 3 d, 5 d, 7 d, 14d after operation(p<0.05). Ki-67 came to express in the superficial layer of anterior corneal stroma 4h after the operation and the highest level observed 3d after opration ,1m later,it came to normal(p<0.01). The number of Ki-67 positive cells in PRK group were more than the Epi-LASIK group 4h, 1d, 3 d, 5 d, 7 d, 14d after operation(p<0.01).α-SMA came to express highly in the superficial layer of anterior corneal stroma 5d after the operation and the highest level observed 1m after opration (p<0.01). The number ofα-SMA positive cells in PRK group were more than the Epi-LASIK group 5 d, 7 d, 14d, 1m, 3m after operation(p<0.01). From the transmission electron microscope, compared with the PRK group, the conjunction of cells in the Epi-LASIK group were more compacted whin 7 days, and the collagen fibers arranged more regularly 1m, 3m after opration.Conclusion:1. Compared with the PRK, the off-flap Epi-LASIK made the lower injury and proliferation response of corneal epithelium.2. Compared with the PRK, the off-flap Epi-LASIK made the lower injury and proliferation response of corneal keratocyte.3. Compared with the PRK, the off-flap Epi-LASIK made the lower potentiality of the transformation to the myofibroblast.4. Compared with the PRK, the off-flap Epi-LASIK made the lower predictability of haze.