Most of the published evidence on photochemical corneal collagen cross‑linkage (CXL) using riboflavin and ultraviolet A (UVA) for keratoconus and keratectasia relates to the technique known as 'epithelium‑off' CXL'. 'Epithelium‑on (transepithelial) CXL' is a more recent technique and less evidence is available on its safety and efficacy. Either procedure (epithelium‑off or epithelium‑on CXL) can be combined with other interventions, and the evidence base for these combination procedures (known as 'CXL‑plus') is also limited. Therefore, different recommendations apply to the variants of this procedure, as follows.
Current evidence on the safety and efficacy of epithelium‑off CXL for keratoconus and keratectasia is adequate in quality and quantity. Therefore, this procedure can be used provided that normal arrangements are in place for clinical governance, consent and audit.
Current evidence on the safety and efficacy of epithelium‑on (transepithelial) CXL, and the combination (CXL‑plus) procedures for keratoconus and keratectasia is inadequate in quantity and quality. Therefore, these procedures should only be used with special arrangements for clinical governance, consent and audit or research.
Clinicians wishing to undertake epithelium‑on (transepithelial) CXL, or the combination (CXL‑plus) procedures should take the following actions:
Inform the clinical governance leads in their NHS trusts.
Ensure that patients and their parents or carers understand the uncertainty about the efficacy and safety of the procedures in the long term and provide them with clear information. In addition, the use of NICE's information for the public is recommended.
Audit and review clinical outcomes of all patients having these procedures for keratoconus and keratectasia (see section 7.1).
Patient selection for these procedures should include assessment of corneal thickness and consideration of the likelihood of disease progression.
The procedures should only be carried out by ophthalmologists with expertise in managing corneal disease and specific training in the use of ultraviolet light or by appropriately trained staff under their supervision.
NICE encourages further research into CXL using riboflavin and UVA for keratoconus and keratectasia, especially epithelium‑on (transepithelial) CXL and the combination (CXL‑plus) procedures. Details of the techniques used should be clearly described. Reported outcomes should include visual acuity, corneal topography and quality of life. Data on long-term outcomes for all types of CXL using riboflavin and UVA for keratoconus and keratectasia would be useful – specifically data about prevention of progression to corneal transplantation and about repeat procedures and their efficacy.