Table 9. Summary of other complications from representative studies across corneal collagen cross-linking protocols in progressive keratoconus.

A-CXL: accelerated corneal cross-linking; ATE-CXL: accelerated transepithelial corneal cross-linking (a high-intensity, short-duration epi-on protocol); CXL: corneal collagen cross-linking; ECD: endothelial cell density (the number of endothelial cells per square millimeter in the cornea); RF: riboflavin; TE-CXL: transepithelial corneal cross-linking

Complication	Study	CXL Protocol	Rate	Notes
Corneal scarring	Ferdi et al., 2019 [21]	Dresden	3.0% at 1 year	Declining over time
Endothelial cell loss	Manumuraleekrishna et al., 2024 [83]	A-CXL (Hypo-osmolar RF)	1 eye	Significant ECD loss
Microbial keratitis	Kandel et al. (Registry), 2024 [24]	A-CXL	1 case	Led to scarring
Need for re-treatment	Ishii et al., 2022 [78]	ATE-CXL	2 eyes	Due to progression
Persistent epithelial defect	Ferdi et al., 2019 [21]	TE-CXL	1.40%	Overall rate
Sterile infiltrates	Kandel et al. (Registry), 2024 [24]	A-CXL	Reported	Resolved with treatment
Stromal edema	Bikbova et al., 2016 [40]	Dresden	Observed	Resolved 6-12 months