Corneal collagen cross-linking with riboflavin and ultraviolet-A light in progressive keratoconus. Results after 10-year follow-up

Riboflavin and ultraviolet-A induced cross-linking (CXL) is a promising therapeutic option to halt the progression of keratoconus. The aim of the study was to prove a long-term stabilizing effect of riboflavin and ultraviolet-A induced collagen CXL in young and otherwise healthy patients with progressive keratoconus and a corneal thickness of at least 400 mu m on average 10 years after treatment. Corneal CXL was performed after removing epithelial tissue by instilling riboflavin 0.1 % solution for 30 min before and during 30 min of ultraviolet-A irradiation (370 nm, 3 mW/cm(2)). This long-term retrospective study included 30 eyes of 20 patients with progressive keratoconus. Preoperative and postoperative examinations on average 10 years after treatment included best corrected visual acuity (BCVA), corneal topography (keratometry values K-MAX, K-MIN and K-Apex), corneal thickness (CT) and if available endothelial cell density. The mean preoperative age was 28 +/- 7 years (range 14-42 years), 4 patients were female (7 eyes) and 16 patients (23 eyes) were male. Preoperatively, the mean K-value on the apex of keratoconus was 62 +/- 13.2 dpt which showed a statistically significant reduction after 10 years to 55 +/- 8.1 dpt (p = 0.001). The mean K-MAX (53 +/- 8.2 versus 49 +/- 6.6 dpt) and K-MIN values (48 +/- 5.5 vs. 45 +/- 5.1 dpt) also showed a statistically significant decrease (p = 0.001). In comparison BCVA also showed a statistically significant preoperative and postoperative difference (p = 0.005). There was a significant improvement of BCVA by a mean of -aEuro parts per thousand 0.13 +/- 0.25 logMAR. The mean change in corneal thickness at the 10-year follow up was 46 mu m (p = 0.001). Bias possibly occurred because of a change of the measurement method from ultrasound pachymetry to optical pachymetry with Oculus PentacamA (R). Neither corneal endothelium nor deeper structures suffered any damage. Only two patients had continuous progression of keratoconus and needed a reapplication of CXL. The results of this study indicate that riboflavin and ultraviolet-A induced corneal CXL is a promising therapeutic option for progressing keratoconus to obtain long-term stabilization. There was a sustained improvement of all K-values and BCVA 10 years after treatment and CXL is minimally invasive and easy to handle. Side effects, such as endothelial damage did not occur.