Corneal cross-linking (CXL) has constituted a corner stone in the treatment of keratoconus for over almost two decades, being used for early, potentially progressive cases. The original procedure for CXL was described as Dresden’s protocol: riboflavin solution is applied on a bare stroma, followed by UV-irradiation. It provides high rates of success and safety; however, it is a lengthy procedure and is accompanied by unfavourable postoperative symptoms related to epithelial defects and haze

Since then, many modifications have been introduced in an attempt to overcome these drawbacks, and have been concentrated on two arms: drug delivery and irradiation. One modification has been to increase energy while shortening the duration, maintaining the total irradiation dose. Recently, a slit lamp mounted device has been developed to convert the patient’s position during the procedure, from a recumbent pose to a sitting one. To minimise postoperative discomfort, the epithelium is preserved in some protocols (Epi-on). In others, riboflavin solution is injected in a femto-second laser created pocket. Applying a contact lens during the procedure aims to widen the candidates’ spectrum by recruiting cases with lower pachymetry. The solution could be also delivered by iontophoresis, to reduce time, preserve the epithelium, and allow irradiation of thin corneas. This procedure could be combined with others to improve corneal irregularity and improve vision quality. This is either by limited corneal ablation, implanting intracorneal ring segments (ICRS), or implanting corneal allogenic intrastromal ring segments (CAIRS). Some studies have expanded the age of therapy to include paediatric patients with severe cases. CXL has also been utilised in selected cases as a line of therapy for the treatment of corneal infections.

The aim of this Special Issue is to highlight most, if not all, different protocols of CXL. We would expect to demonstrate the degree of success for each modification, to assess the results of additional procedures, and to check the efficacy in other indications. Authors are encouraged to publish in this edition to present their techniques among the wide spectrum of currently available techniques. This will allow a direct comparison of benefits for authors and readers. We welcome both original research and review articles.

Potential topics include but are not limited to the following:

• Epithelium-preserving (Epi-on) CXL
• Contact lens assisted CXL
• CXL with femtosecond laser pocket
• Accelerated CXLs
• Iontophoresis-assisted CXL
• CXL using slit-lamp mounted devices
• CXL for paediatric age groups
• Photoactivated chromophore for infectious keratitis (PACK-CXL)
• CXL combined with excimer laser ablation
• CXL with intracorneal ring segments (ICRS)