Cross-Linking: Interaction between

• Riboflavin and UVA in order to produce O- (singulet oxigen) with oxidative dexaminhation and carbo-amidic bonds production

• This reaction require three elements:– Riboflavin

– UVA

– Collagen

INDEPENDENTLY FROM RIBOFLAVIN TRANS-EPITHELIAL DELIVERY SYSTEM the epithelium leaved in situ and soaked by

riboflavin, induces a «shielding» effect absorbing over 90% of UV-A radiation, confining CXL penetration in a surface level under 100 µm

The Epithelium should be always removed to ensure a deep and sufficient interaction between UV A, Riboflavin

and collagen molecules, maximizing the CXL effect !!!

UV A photons “In situ” Epithelium , without Riboflavin, induces a “shield” effect

Absorbing about 30 % of UV A radiation !

Corneal Epithelium