Repeat corneal collagen cross-linking after failure of primary cross-linking in keratoconus

Background Primary corneal collagen cross-linking (CXL) stabilises 96% of progressive keratoconus. There is limited evidence for the treatment of choice when this fails. We present 10 years of repeat CXL and compare with our published experience of primary CXL to (1) identify perioperative risk factors of primary CXL failure and (2) demonstrate the safety and efficacy of repeat CXL. Methods Patients undergoing repeat accelerated epithelium-off CXL at St James’s University Hospital, Leeds, UK January 2012–August 2022 were identified through electronic patient record, and compared with a previously published cohort of primary CXL patients at the same site. Results Twenty-one eyes underwent repeat CXL. The mean interval between primary and repeat CXL treatments was 47.1 months (SD 22.5). Twenty (95%) eyes stabilised after repeat CXL at a mean follow-up of 29.9 months. These cases were compared with 151 cases of primary CXL from our previous study. Patients failing primary CXL were significantly younger (21.3 years (SD 7.0) vs 26.7 years (SD 6.5), p=0.0008). Repeat CXL and primary CXL induced a similar amount of flattening of Kmax (−1.2 D (SD 3.9) vs −0.7 D (SD 4.4), p=0.22). A small, but clinically insignificant, improvement in best-corrected visual acuity was found in the repeat CXL group (−0.04 (SD 0.17) vs −0.05 (SD 0.13), p=0.04). No complications of repeat CXL were noted. Conclusion Younger age may be associated with failure of primary CXL. Repeat CXL is an effective and safe treatment for progressive keratoconus despite primary CXL.