Corneal collagen cross-linking for the treatment of progressive keratoconus: 3-year prospective outcome

Objective: To assess the long-term effects of treatment of progressive keratoconus with ultraviolet A-riboflavin collagen cross-linking (CXL). Design: This was a prospective clinical study. Participants: Seventeen eyes of 17 patients with progressive keratoconus were treated with CXL. Methods: Patients were examined preoperatively, at week 1, months 1, 3, 6, 9, 12, 24, and 36 after treatment. We assessed uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA), refraction, biomicroscopy and fundus appearance, intraocular pressure, endothelial cell density (ECD), corneal topography, minimal corneal thickness (MCT), macular optical coherence tomography, axial length, and corneal biomechanics with the ocular response analyzer. Results: Comparing the 36-month time point results with pretreatment values, we found that UCVA and BSCVA were unchanged. Steepest meridian keratometry (D) and mean cylinder (D) did not show significant change compared with pretreatment values but showed a slight increase as compared with the 24-month time point (53.9 vs 51.7 vs 52.5, and 10.5 vs 8.1 vs 9.2 before, at 24 months, and at 36 months, respectively). Axial length (mm) showed an elongation trend throughout the follow-up period (24.56 vs 24.61 [p = 0.04] vs 24.71 [p = 0.05], before, at 24 months, and at 36 months, respectively). No significant change was observed in ECD, corneal hysteresis and corneal resistance factor, MCT, or foveal thickness. Conclusions: Three-year results after CXL show stable visual acuity, stable corneal thickness, and stable corneal biomechanical parameters. The decreasing trend in keratometry values that was observed during the first 2 years after CXL was no longer evident. Longer follow-up is needed to decide whether it is a first sign of loss of achieved stability and resumption of keratoconus progression.