Cross-Linking of Corneal Collagen with UVA and Riboflavin for the Treatment of Corneal Disease

Introduction In recent years, reduced corneal biomechanics have been identified as an important element in the pathogenesis of various corneal diseases. The biomechanical characteristics of a connective tissue such as strength and resistance against mechanical stress are indispensable prerequisites to maintain regular shape and function of that tissue. Intraand intermolecular cross-links between collagen molecules are essential elements of these biomechanical properties. Accordingly, collagen cross-links occur physiologically in all organs and tissues with certain biomechanical characteristics. In other surgical fields, cross-linking has been used for decades to increase the biomechanical properties of connective tissue structures: in cardiac surgery, porcine aortic valve bioprosthesises are treated with glutaraldehyde prior to implantation to ensure increased cross-linking, which increases biomechanical resistance against biodegradation. Additionally, in otolaryngology, polymers inducing crosslinking are used in the treatment of destabilized vocal cords and for nasal reconstruction. In the cornea, a variety of conditions such as primary acquired (keratoconus and pellucid marginal corneal degeneration) and secondary induced (iatrogenic keratectasia after refractive laser surgery) ectatic disorders lead to a reduced biomechanical resistance. Corneal collagen cross-linking with riboflavin/UVA (CXL) represents a new approach to these diseases. To assist researchers and clinicians interested in the field, this article attempts to provide a structured overview on the current state of the method, basic principles, technique, and application of CXL in primary and iatrogenic keratectasia. Furthermore, it addresses safety issues and potential complications of the method.