The gold standard corneal crosslinking (CXL) technique involves the initial step of epithelial removal, in order to achieve a sufficient treatment effect (meaning: stabilisation of progressive keratoconus (KC). Our aim is to evaluate the effects of transepithelial CXL (TE-CXL), whereby the epithelium is left intact and the cornea is instead treated by a solution composed of 0.1% riboflavin, combined with enhancers, after which standard CXL is performed. This solution seems to facilitate riboflavin penetration into the corneal stroma through the intact epithelium. The investigators expect to achieve a similar effect of TE-CXL with the advantage of a faster healing time and less risk of infections.

Inclusion Criteria:

• Documented progressive KC (by Pentacam and/or corneal topography imaging).
• A clear central cornea.
• A minimal corneal thickness of ≥ 400 µm at the thinnest corneal location (Pentacam imaging).
• Minimal Snellen corrected distance visual acuity of ≥ 0.4.
• Patient age of ≥ 18 years.

For this research study, the inclusion parameters will be the same as mentioned above, with the following additional inclusion criteria:

• Documented progression of KC, as demonstrated by anterior segment imaging and/or corneal topography:

  o Defined an increase in maximal keratometry, steepest keratometry, mean keratometry or topographic cylinder value by ≥ 0.5 D over the previous 6 months and/or a decrease in thinnest pachymetry

• Documented progression of KC defined by increase in refractive cylinder of ≥ 0.5 D over the previous 6 months

Exclusion Criteria:

• Presence of corneal scars.
• History of epithelial healing problems.
• Presence of previous ocular infection (such as herpes keratitis).
• Patients who are pregnant and/or breastfeeding.