EXPERIMENTAL STUDY OF A DONOR CORNEA UV CROSS-LINKING ENZYMATIC STABILITY

Purpose. To study the stability of a crosslinking modified donor cornea to collagenase preserved in the Borzenok-Moroz solution.Material and methods. Donor cornea (n=24) divided into 4 groups were the target of the research. All cornea were preserved in the Borzenok-Moroz solution for 24 hours according to standard procedure (2) before the experiment start. The first group contained only the donor cornea preserved in the BorzenokMoroz solution (n=6). The second group included preserved donor corneas with the added riboflavin treated according to the crosslinking method (n=6). The third group was formed by preserved donor corneas treated with collagenasa: result was evaluated in dynamics 24 hours (n=3) as well as 72 hours (n=3) later. The forth group consisted of preserved donor corneas with the added riboflavin after cross-linking and treated with collagenasa: result was evaluated in dynamics 24 hours (n=3) as well as 72 hours (n=3) later. Scanning electron microscopy (SEM) was carried outResults. The first group of corneas was used for reference, and according to the SEM results the corneal stroma was presented by plates of collagen protein fibers strictly oriented. In the second corneal stroma group a thickening of collagen fibrils was observed as well as a reduction of distance between the collagen plates and a more compact stacking of plates under influence of riboflavin and ultraviolet compared to the reference group. In the third group of corneas, upon collagenase impact a destruction of collagen fibrils, a breaking of the longitudinal collagen plates orientation, a disorder of protein structure were also noted after 24 hours, the remaining coagulated protein fractions were visualized. Corneal collagen fibrils in the fourth group treated with riboflavin, ultraviolet and collagenase after 24 hours retained their structure and orientation and a more compact stacking of collagen plates was noticed compared to the third group corneas. Dynamic evaluation of collagenase impact on the third and fourth groups after 72 hours showed that in the group 4 the impact of collagenase on the cornea was minimal, the structure and orientation of the collagen layers were preserved.Conclusions. Cross-linking procedure has a stabilizing physical-chemical effect on corneal collagen fibrils, enhances biochemical resistance to proteolytic tear enzymes and inflammatory cells what can be effective in treatment of corneal diseases.