Effects of Riboflavin and Ultraviolet Illumination on the Biomechanical Properties of Conjunctiva

Purpose: Our experiment evaluated the biomechanical effects of riboflavin and ultraviolet A illumination, in terms of covalent bonding, permeability, and indentation rupture force, on excised cattle conjunctiva.

Materials and methods: Cattle conjunctiva was extracted and divided into the treatment group, which was soaked in riboflavin, followed by ultraviolet light illumination, and the control group. Samples were subsequently analysed on a Fourier transform infrared spectrum test to identify the presence of amide bonds, a permeability test to assess the diffusion of methylene blue across conjunctiva, and an indentation rupture force test.

Results: The Fourier transform infrared spectrum test showed a significantly increased amide I band after treatment (p = 0.043), as well as in amide II, amide A, and amide B bands. The permeability test showed a reduced permeability to methylene blue after treatment (n = 25) compared to the control (n = 24; p = 0.03). The indentation rupture test showed a higher maximal rupture force in the treated samples (n = 10; p = 0.07).

Conclusions: The study suggested that riboflavin and ultraviolet A illumination (commercially available as collagen crosslinking) strengthened cattle conjunctiva by increasing its amount of covalent bonds, reducing its permeability, and possibly improving its resistance to rupture. This is the first study in the collagen crosslinking literature on the biomechanical properties of conjunctival tissue.