Molecular processes of corneal collagen cross-linking in keratoconus therapy

Abstract

Corneal collagen cross-linking (CXL) with riboflavin and UVA light is a therapeutic procedure to restore the mechanical stability of corneal tissue. The treatment method applies to pathological tissue changes, such as keratoconus. It induces the photochemical formation of new collagen cross-links. Although therapeutic effects are indisputable, the exact molecular process of CXL and how cross-links are formed is still unclear. In this work, Fouriertransform infrared (FT-IR) spectroscopy is used to investigate the cross-linking process. For that purpose, in-situ experiments with porcine corneas are carried out using attenuated total reflection (ATR) spectroscopy. Furthermore, IR micro-spectroscopic imaging in transmission mode is used to investigate thin tissue sections of the cornea and initial approaches for the distinction of cross-linked and untreated tissue by IR microspectroscopic imaging were performed. Multivariate methods are applied to access changes that occur as a result of CXL. It is shown that spectral changes after cross-linking are caused predominantly by an increase of methyl- and methylene groups as well as primary and secondary amines. In addition, a decrease of carbonyl groups could be observed.

Keywords

• corneal collagen crosslinking
• ft-ir spectroscopy
• microspectroscopic imaging
• attenuated total reflection