The change of collagen in rabbit conjunctiva after conjunctiva cross-linking

Abstract Background We aimed to determine the ultrastructural changes of collagen fibrils in the rabbit conjunctiva after conjunctiva cross-linking using riboflavin and UVA light of 45mW / cm 2 irradiation intensity. Conjunctiva cross-linking may increase conjunctiva stiffness. Methods The super-temporal quadrant of the right eyes of twenty-four adult rabbits were treated with topical riboflavin solution (0.25%) followed by irradiation with UVA light (45mW/cm 2 ) for 4 min. After 3 weeks, the collagen fibrils in fibril bundles were examined with electron microscopy. Immunohistochemical staining was applied to detect the expression of collagen I and III in the rabbits’ conjunctiva. Results The diameter of collagen fibrils in the fibril bundles varied slightly and ranged from 30 to 60 nm in control group conjunctival stroma. While in the treatment group, the diameter of collagen fibrils ranged from 60 to 90 nm. Thickest collagen fibrils were observed in the treatment group (fibril diameters up to 90 nm), whereas thickest collagen fibrils in control group conjunctival stroma are considerable smaller (up to 60 nm in diameter). However, both of the thickness of collagen fibrils displayed a unimodal distribution. Collagen I and collagen III were increased after treatment with riboflavin and UVA light of 45 mW/cm 2 .Conclusions The data indicate that in rabbits, conjunctiva cross-linking with riboflavin and UVA light of 45 mW/cm 2 for 4 min is relatively safe and does not induce ultrastructural alterations of conjunctiva cells. The conjunctiva cross-linking riboflavin and UVA light of 45 mW/cm 2 can increase the diameter of collagen fibrils, but the average density of collagen I and collagen III have no statistical significance.