The original cross-linking procedure (commonly referred to as the ‘Dresden protocol’ [1]) involved anaesthetising the eye (for example with proxymetacainhydrochloride 0.5% drops), removing the central 8-10mm of the epithelium and applying a riboflavin solution (0.1% riboflavin-5-phosphate and 20% dextran T-500) to the corneal surface 30 minutes before irradiation and at 5 minutes intervals during the course of a 30 minute exposure to 370 nm UVA with an irradiance of 3 mWcm-2.

After treatment, antibiotic eye drops are applied and a therapeutic soft contact lens with good oxygen transmissibility placed upon the eye to decrease pain without decreasing the quality of the regrowing epithelium. Application of topical antibiotics is required for 1 week after the operation and mild steroids may also be prescribed. Patients are usually pain-free within 5-7 days when the contact lens is removed [2].

The well documented clinical drawbacks to this technique are the postoperative discomfort associated with removal of the corneal epithelium, the length treatment time and its unsuitability for the treatment of very thin keratoconus corneas (less than 400 microns) [3].

CXL procedure

CXL procedure

[1] Wollensak, G. et al. Riboflavin/ultraviolet-a-induced collagen crosslinking for the treatment of keratoconus. American Journal of Ophthalmology. 2003;135:620-627.

[2] Abad, J. and Panesso, J. Corneal collagen cross-linking induced by UVA and riboflavin (CXL). Techniques in Ophthalmology. 2008;6:8-12.

[3] Spoerl, E. et al. Safety of UVA-Riboflavin Cross-Linking of the Cornea. Cornea. 2007;26(4):385-9.