Long-term follow-up of riboflavin/ultraviolet A (370 nm) corneal collagen cross-linking to halt the progression of keratoconus

Aims To determine long-term efficacy of riboflavin/ultraviolet A corneal cross-linking (CXL). Methods Thirty patients (30 eyes) who had undergone CXL following epithelial removal 4-6 years previously were examined. Results At 1-year mean, spherical equivalent error (SEQ) increased by +0.72 dioptres (D) (p<0.002), corrected distance visual acuity (CDVA) improved (p<0.005), mean simulated keratometry (Sim K) reduced by 0.27D (p<0.04), cone apex power (CAP) reduced by 0.4D (p<0.02), and secondary astigmatism improved (p<0.03) compared with preoperative values. At 4-6 years, mean SEQ increased by +0.82D (p<0.001), CDVA improved (p<0.03), mean Sim K reduced by 0.84D (p<0.00001), CAP reduced by 1.16D (p<0.0005), and root mean square (RMS) (p<0.0001), coma (p<0.0001), secondary astigmatism (p<0.005) and pentafoil (p<0.05) decreased compared with preoperative values. At 4-6 years, mean Sim K reduced by 0.59D (p<0.0005), CAP reduced by 0.76D (p<0.02), RMS (p<0.001), coma (p<0.002) and secondary astigmatism (p<0.02) reduced and central pachymetry increased (p<0.05) compared with 1 year. No treated eyes progressed. None lost >1 line of CDVA. Seven untreated fellow eyes progressed. Conclusions CXL is an effective and safe treatment with up to 4-6 years follow-up. Improvements in topographic and wave-front parameters evident at 1 year continue to improve at 4-6 years.