The Study Of Cross-Linked Cornea's Resistance Against Enzymatic Digestion From The Experiments On Rabbits

Part ? An experimental study of UV-X corneal collagen cross-linking instrument's effect on rabbitObjective:Through the corneal collagen cross-linking and related experiments by UV-X corneal collagen cross-linking instrument on rabbit cornea, to verify the effects of the instrument and make evaluation and lay the foundation for further experiment.Methods:A total of 10 Japanese white rabbits were studied and divided into normal control group(one rabbit) and one eye of 9 rabbits as experimental group while the other as control group.All the eyes' cornea epithelial of the 9 rabbits were scraped,then the experimental group received corneal collagen cross-linking by UV-X corneal collagen cross-linking instrument;Three rabbits were sacrificed at 1 day,3 days,7 days after the operation.Both of the eyes' corneas were taken and were further studied by light microscope(HE staining,VG staining),electron microscope.Results:each eye in the experimental group received cornealcollagen cross-linking smoothly.HE staining showed that all the corneas had edema and inflammatory reactions,but the degree became ease with time passed by.At the 7th day postoperative,no significant corneal edema was observed,also significantly reduce inflammatory reaction.The degree of inflammation and edema were both lighter in the control group,but its recovery was slower as well.Through the difference between the quantities of corneas' grayscales, experimental group's density of collagen fiber was obviously higher than that of control group,and the density was higher on fiber near epithelial in cross-linked corneas.Electron microscopy showed that in experimental group cells had a little edema,the connection between cells was tight,the fiber arranged neatly.While in control group,cells swelled more severe,Content except several endoplasmic reticulum were still visible,others were dissolved.The nucleus became bigger while the density decreased.Collagen fiber spacing increased.Conclusion:Application of UV-X corneal collagen cross-linking instrument for corneal collagen cross-linking is stable,safe and effective.Corneas after applying with the instrument were thicker and the fiber arranged more intensive.Part ? An experiment study on enzyme digestion inhibition of Corneal Cross-linkingObjective Comparative observation of three kinds of protease's(pepsin,trypsin and collagenase) digestion on cross-linked and uncross-linked rabbit eye corneas,then to verify wether the corneal cross-linking can strengthen the inhibition of enzyme digestion.Methods A total of 9 Japanese white rabbits were studied and randomly divided into 3 groups.All the eyes' cornea epithelial of the 9 rabbits were scraped,randomly take an eye as experimental group and conducted corneal collagen cross-linking.Then they sacrificed and took corneas.Put the corneas into corresponding enzyme solutions in their optimum temperature. Observe the change of the cornea during the digestion and record the time when the corneas were digested completely.According to the former experiment, a total of 18 Japanese white rabbits were studied and randomly divided into 3 groups. Two rabbits' residual corneas were taken out at 1 day,3 days,7 days and further studied by light microscope(HE staining).Results Time spent on the corneas' fully digestion:Pepsin-experimental group were66?65?59 days,the average was 63.33±2.19 days,while the control group were 61?59 ? 52 days,the average was 57.33 ±2.73 days.Trypsin-experimental group were 4?4?4 days,the average was 4 days,while the control group were 3?3?2days,the average was 2.67±0.33 days.Collagenase-experimental group were 7?3?5 days,the average was 5±1.15 days,while the control group were 2?2?2 days,the average was 2 days.All experimental groups were obviously longer than control groups(P<0.05).Corneas changed over time in the enzyme solutions-shrivel,thinning and dissolved at last.Experimental groups changed a little slower than control groups.The HE staining showed that With the time of corneas immersed in enzyme solutions increased,cells became swelling, structure disappeared,epithelials became thinner gradually.But the changes in experimental groups were slower than control groups.Conclusion Corneal cross-linking can strengthen the inhibition to enzyme digestion of corneas.