The incidence of progression (23% at one year follow-up and 18% at two years, respectively) is considerably higher than in previously reported results of corneal collagen crosslinking (CXL) in eyes with mean Kmax of 58.0D or greater. Researchers in Switzerland evaluated the effectiveness standard Dresden epi-off CXL in treating 61 eyes of 56 patients with steep eyes and documented progressive keratoconus.

Mean Kmax was 63.9±6.1D preoperatively and 62.9±5.9D after one year. This represented a significant decrease in steepness. Mean pachymetry decreased significantly from 433.7±44.8μm preoperatively to 423.0±41.8μm at one year. Progression occurred in 14 of the 61 eyes (23%) at one year, and five (8.2%) steepened more than 2.0D. In the group of 50 eyes with two-year follow-up, mean Kmax was 63.0±5.0D before CXL and decreased to 61.5±4.8 at two years. Nine of the 50 eyes 18%) showed an increase of Kmax of one diopter or greater.

The study concluded that the practitioner should discuss with the patient preoperatively the higher rate of postoperative progression as well as consider lamellar or penetrating keratoplasty as an alternative first-line treatment.