Cross-linking of collagen refers to the ability of collagen fibrils to form strong chemical bonds with adjacent fibrils. In the cornea, collagen cross-linking occurs naturally with aging due to an oxidative deamination reaction that takes place within the end chains of the collagen

Riboflavin
A photosensitizer is a molecule that absorbs light energy and produces a chemical change in another molecule.

In CXL, Riboflavin is used as the photosensitizer. It is safe systemically and can be adequately absorbed by the corneal stroma topically. It has an absorption peak at 370 nm.

UV Light
As the absorption peak of riboflavin was noted to be 370 nm, UV-A light was found to be ideal for CXL, while at the same time protecting the other ocular structures. The total fluence required was found to be 5.4J/cm2.

The Bunsen Roscoe law states that the photochemical effect should be similar if the total fluence remains constant. Based on this, various protocols have been devised with different combinations of the intensity and duration of UV-A exposure.[4] However, it has been noted that CXL fails to be effective once the energy intensity exceeds 45mW/cm2.

college cross linkages for keratoconus CXL
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