Treatment of keratoconus by collagen cross linking

Background. We were able to show a significant increase in corneal stiffness of rabbit and porcine eyes after combined riboflavin/UVA-induced collagen cross-linking. In this study, we tried to treat keratoconus patients with this method to stop the progression of corneal ectasia. Patients and methods. We treated 16 eyes of 15 patients with progressive keratoconus and mostly moderate keratectasia (48-56 dpt). After removal of the epithelium (7 mm circle divide), riboflavin solution was applied on the cornea, which was irradiated with UVA (370 nm, 3 mW/cm(2)) at a distance of 1 cm for 30 min. Post-operative follow-up controls were conducted every 3 months in the first year and then every 6 months, always including visual acuity testing, corneal topography and measurements of endothelial cell density. The follow-up time was between 1 and 3 years. Results. Progression of keratectasia was stopped in all patients. Best corrected visual acuity and the maximal keratometry values improved slightly in about 50% of the cases. In all patients corneal transparency, the degree of keratectasia registered by corneal topography and the density of endothelial cells remained unchanged within the follow-up time. No negative side-effects were observed. Conclusions. Our results show that collagen cross linking might be a useful conservative treatment modality to stop the progression of keratoconus. By this means the need for keratoplasty might be significantly reduced. Given the simplicity of the technique and minimal costs of the treatment it might also be well suited for developing countries. Further studies are envisaged to exclude long-term side effects and to evaluate the long term durability of the mechanical stiffness effect.