[Corneal crosslinking for keratoconus: real-life data and Committee for Refractive Surgery (KRC) recommendations]

Keratoconus is a chronic corneal ectasia characterized by a progressive course frequently starting in young age, in which in advanced stages often only a corneal transplantation can help to restore vision. Since the early 2000s, crosslinking has been available as a surgical procedure that can halt the progression of keratoconus. Crosslinking is a low-risk procedure with a high chance of success. To ensure that the costs of crosslinking are covered by the statutory health insurance in Germany, medical evidence of progression must be provided. In the assessment of the Federal Joint Committee on the remuneration for crosslinking a progression is defined as an increase in maximum corneal refractive power (Kmax) or astigmatism in subjective refraction by at least 1 dpt or a decrease in the base curve of the best-fitting contact lens by 0.1 mm. Once the indications for crosslinking have been established, various procedures are available. The standard Dresden Protocol has proven to be a safe intervention in several studies and remains the reference standard for crosslinking procedures but it has some limitations with a minimum pachymetry of 400 µm after corneal abrasion and a long procedural duration. Accelerated crosslinking protocols with increased irradiation intensity and a correspondingly reduced irradiation duration have a similar effectiveness with a lower risk profile. Epi-on protocols, which do not involve epithelial abrasion, reduce the risk of bacterial infections but are less effective than epi-off protocols. New protocols focus on controlling the intensity and duration of irradiation based on pachymetry and topography. The sub-400 protocols made possible by this approach show a high reduction in progression with low endothelial damage despite low pachymetry. The criteria of the Committee for Refractive Surgery (KRC) define the specific range of indications for crosslinking of both the Professional Association of Ophthalmologists in Germany (BVA) and the German Society of Ophthalmology (DOG).