Comparative study of long-term outcomes of accelerated and conventional collagen crosslinking for progressive keratoconus

Purpose To compare the long-term outcomes of accelerated corneal collagen crosslinking (CXL) to conventional CXL for progressive keratoconus. Patients and methods Comparative clinical study of consecutive progressive keratoconic eyes that underwent either accelerated CXL (9 mW/cm(2) ultraviolet A (UVA) light irradiance for 10 min) or conventional CXL (3 mW/cm(2) UVA light irradiance for 30 min). Eyes with minimum 12 months' follow-up were included. Post-procedure changes in keratometry readings (Flat meridian: K1; steep meridian: K2), central corneal thickness (CCT), best spectacle-corrected visual acuity (BSCVA), and manifest refraction spherical equivalent (MRSE) were analysed. Results A total of 42 eyes were included. In all, 21 eyes had accelerated CXL (20.5 +/- 5.5 months' follow-up) and 21 eyes had conventional CXL group (20.2 +/- 5.6 months' follow-up). In the accelerated CXL group, a significant reduction in K2 (P = 0.02), however no significant change in K1 (P = 0.35) and CCT (P = 0.62) was noted. In the conventional CXL group, a significant reduction was seen in K1 (P = 0.01) and K2 (P = 0.04), but not in CCT (P = 0.95). Although both groups exhibited significant reductions in K2 readings, no noteworthy differences were noted between them (P = 0.36). Improvements in BSCVA (accelerated CXL; P = 0.22 and conventional CXL; P = 0.20) and MRSE (accelerated CXL; P = 0.97 and conventional CXL; P = 0.54) were noted, however were not significant in either group. Conclusion Accelerated and conventional CXL appear to be effective procedures for stabilising progressive keratoconus in the long-term.