Comparative Research Of Corneal Wound Healing Response After Epipolis Laser In-Situ Keratomileusis And Flap-Free Epipolis Laser In-Situ Keratomileusis In Rabbits

Objective To evaluate the effect of different way of corneal epithelium wound healing to the early corneal response on Epi–LASIK(epipolis laser in-situ keratomileusis) compared to Flap -free Epi–LASIK(Flap -free epipolis laser in-situ keratomileusis) in rabbits.The study includes two partsExperiment 1 To study the different way of corneal epithelium wound healing on Epi–LASIK(epipolis laser in-situ keratomileusis) compared to Flap-free Epi–LASIK(Flap-free epipolis laser in-situ keratomileusis) in rabbitsExperiment 2 To study the effects of different way of corneal epithelium wound healing to the early Inflammatory response on Epi–LASIK(epipolis laser in-situ keratomileusis) compared to Flap -free Epi–LASIK(Flap -free epipolis laser in-situ keratomileusis) in rabbits.MethodsExperiment 1 Epi-LASIK or Flap -free Epi–LASIK was performed on New Zealand rabbits eyes ,t reated-eyes were randomly divided into four groups(1d,2d,4d,7d ) and rabbits eyes without treatment were served as blank controls. The way of the corneal epithelium wound healing was observed at 1,2,4,7 days after surgery by light microscope and electron microscope.The number of keratocytes cells in the central anterior stroma were counted from hematoxylin-eosin-stained specimens of Epi–LASIK and Flap-free Epi–LASIK .The expression of Basic fibroblast growth factor(bFGF) in corneal stroma were assessed by Immunohistochemistry staining.Experiment 2 Epi-LASIK or Flap -free Epi–LASIK was performed on New Zealand rabbits eyes ,t reated-eyes were randomly divided into four groups(1d,2d,4d,7d ) and rabbits eyes without treatment were served as blank controls. To compare the changes of corneal wound healing between Epi-LASIK groups and Flap-free Epi–LASIK groups, including keratocytes apoptosis,the number of inflammatory cells in the central anterior stroma and expression of Interleukin (IL-1β),expression of nuclear factor(NF)-κB for ablation area of corneal epithelium and stroma .ResultsExperiment 1(1)Morphology : Light microscope and electron microscope demonstrated that at the first day after surgery the basement membrane of the corneal epithelium in Epi-LASIK specimens conjuncted with stroma tightly. At the second day after surgery,there was the edema of the epithelium flap in the Epi–LASIK specimens. The perinuclear space was expanded and there was the edema of the chondriosome too. At the 4 to 7 days after the surgery ,the edema of epithelium in the Epi–LASIK specimens resolved gradually. At the first day after surgery , there was one layer of neogenesis corneal epithelium cell covered the filed of operation in Flap-free Epi-LASIK specimens .It would increased gradually in the 7days.There was no edema in this process. At the7 days after the surgery the epithelium cell were 5-6 sheets and the epithelium cell accreted with the stroma well. The epithelium cell basilar membrane were both integrity. The alignment of the fiber in the corneal stroma is regularity.( 2) Expression of bFGF in the cornea :There was no statistically significant difference in the expression of bFGF in the corneal stroma between Epi-LASIK and Flap-free Epi-LASIK specimens at 1,7days after surgery.But there was a significant increase in the expression of bFGF in the corneal stroma of Flap-free Epi–LASIK compared to Epi–LASIK specimens at 2,4 days after surgery (p<0.05) .( 3) The number of keratocytes :There was no statistically significant difference in the number of keratocytes cells in the corneal stroma between Epi-LASIK and Flap-free Epi-LASIK specimens at 1,2 and 7days after surgery .There was a significant difference for the more number of keratocytes cells in the corneal stroma of Flap-free Epi-LASIK compared to Epi-LASIK at 4days after surgery (p<0.05).Experiment 2(1)Expression of IL-1βin the cornea : No difference in the expression of IL-1βin the corneal epithelium between Epi–LASIK and Flap-free Epi–LASIK at 1,2,4,7 days (p>0.05),and there was a significant decrease in the expression of IL-1βin the corneal stroma of Flap-free Epi–LASIK compared to Epi–LASIK at 1,4,7 days (p<0.05) and no difference at 2 days after surgery.( 2) Expression of NF-κB in the cornea :There was a significant decrease in the expression of NF-κB in the corneal epithelium of Flap-free Epi–LASIK compared to Epi–LASIK at 1,2,7 days after surgery(p<0.05) and no difference at 4 days after surgery(p>0.05) .There was a significant decrease in the expression of NF-κB in the corneal stroma of Flap-free Epi–LASIK compared to Epi–LASIK at 2,4 days after surgery(p<0.05) and no difference at 1,7 days after surgery(p>0.05).( 3) The number of inflammatory cells:There was statistically significant difference increase the number of inflammatory cells in the corneal stroma of Epi–LASIK compared to Flap-free Epi–LASIK at 1,2 day after surgery.(p<0.05)and no inflammatory cell infiltrated for Flap-free Epi–LASIK,Epi-LASIK groups at 5,7 days postoperatively.( 4) Keratocyte apoptosis:At 1,7 days after surgery, no difference in TUNEL positive cells were seen between specimens of Epi-LASIK and Flap-free Epi–LASIK ;There was a significant difference for the more number keratocyte apoptosis in Epi–LASIK compared to Flap-free Epi–LASIK specimens at 2,4days after surgery(p<0.05).ConclusionThere were the specific way of both the epithelium removal and epithelium healing in Flap-free Epi–LASIK. It's advantageous to lessen the Inflammatory response and stimulated symptom after the surgery. It's also good for the corneal wound healing and It maybe would reduce the occurrence of Haze.