Long-term outcome of corneal collagen crosslinking with riboflavin and UV-A irradiation for keratoconus

Purpose To evaluate long-term outcomes of corneal collagen crosslinking (CXL) using riboflavin and UV-A irradiation and to determine when to repeat CXL. Methods In this retrospective consecutive interventional case series 131 eyes of 131 patients (95 male, 36 female, mean age 29.7±11.4 years) between 2006 and 2016 received standard CXL (Dresden protocol, epithelium-off) for progressive keratoconus. Corrected distance visual acuity (CDVA) and corneal tomography (K 1 , K 2 , K max ) were repeatedly recorded 1 year (n=103 eyes) to 10 years (n=44) postoperatively. Only one eye per patient was included. Paired t-test or Wilcoxon matched-pairs signed rank test was used for parametric and nonparametric data, respectively. Results 1 to 3 years pre operatively, median K 2 significantly increased by 1.1D (p<0.001). Post operatively, median K 2 increased by 0.1D after 1 year, then decreased over the remaining postoperative period by 0.85D (p=0.021). Median apical corneal thickness decreased by 16µm (p=0.012) after 5 years and then returned to preoperative values. Mean CDVA showed a significant improvement (decrease in logMAR 0.12 after 10 years, p=0.010). K max fluctuated without significant change. CXL non-responders, defined by a postoperative increase in K max >2D, increased from 16% after 5 to 33% after 10 years. Risk factors for non-response were young age, high astigmatism, thin cornea, and atopic dermatitis. 4 eyes were re-treated 3–4 years after first CXL without complications and keratoconus stabilized thereafter. Conclusions CXL can slow or stop keratoconus progression. However, as the number of responders declines after 5 years, patients with risk factors may require re-treatment.