Abstract
Purpose :
To evaluate long-term (up to 10 years) efficacy and safety of corneal collagen crosslinking with riboflavin and UV-A irradiation (CXL) for progressive keratoconus, and to determine when to repeat CXL.
Methods :
168 eyes of 131 patients (male:female = 95:36) were treated with standard CXL, comprising abrasion, application of iso-osmolar riboflavin/dextran eye drops for 30 min, and application of UV-A irradiation at 3 mW/cm2 for 30 min. Retrospective follow-up was 1 (n=103 eyes) to max. 10 years (n=44 eyes). Inclusion criteria were increase of maximum surface radius of curvature (Kmax measured with Pentacam HR) >1D and corneal thickness >400 µm after abrasion. Paired t test or Wilcoxon matched-pairs signed rank test were used for parametric or nonparametric data, respectively.
Results :
1 to 3 years preoperatively, median Kmax and median K2 significantly increased by 1.5D (p=0.001) and 1.1D (p<0.001) respectively. 9 to 6 months preoperatively, both Kmax and K2 increased by 1D (p=0.007) and 1.4D (p<0.001). Apical corneal thickness decreased by 12µm at 1-3 years preop (p=0.003).
After CXL, median K2 increased by 0.1D after 1 year, but then decreased over the remaining postoperative period by 0.85D (p=0.021) after 10 years. Mean apical corneal thickness decreased by 11µm (p<0.001), 9µm (p=0.014) and 3µm (p=0.358) after 3, 7 and 10 years, respectively. Median Kmax showed high variation with no significant change. After 10 years, a 0.1D increase was noted (p=0.276). Mean best corrected visual acuity (logMAR) significantly increased by 0.14 after 2 years (p<0.001), by 0.15 after 5 and 10 years (p=0.006 and p=0.003).
CXL-responders were defined by postoperative stabilisation of Kmax, i.e. increase <2D or any decrease of Kmax. 1, 7 and 10 years after CXL, 87.8%, 81.1% and 66.7% of eyes met the responder criteria, respectively. 4 eyes were re-treated at 3, 4, 5 and 5 years after first CXL with no complications and keratoconus stabilised thereafter.
Conclusions :
As shown before, CXL can slow down or even stop the progression of keratoconus. However, beyond 5 years after treatment, we noted a continuous decrease of the responder rate. Therefore we advocate to examine patients at regular intervals especially after 5 years post CXL, to recognize and re-treat a progression early.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.