On the basis of Wollensak et al. [1] demonstrating that riboflavin/UVA cross-linked pig corneas placed in a humidity chamber swell less than untreated corneas, cross-linking was proposed as a therapeutic option for the treatment of corneal oedema, such as seen in Bullous Keratopathy. In practice however the standard riboflavin/UVA cross-linking protocol appears to produce only short term improvements in pain, irritation and discomfort, and sometimes (but not always) results in a reduction in corneal thickness [2,3]. Modified riboflavin/UVA cross-linking techniques in which swollen corneas are dehydrated to a normal thickness prior to treatment have produced favourable results, with distinct reductions in corneal thickness and a reduction in patient discomfort immediately post surgery [4,5] and up to 8 months post treatment [6].

Although the effects of cross-linking on corneal oedema appear to be transient and may not prevent the need for corneal transplantation in conditions that involve corneal swelling, it does have the potential to significantly improve patients’ visual comfort whilst waiting for a transplant and possibly extend the time interval for an upcoming corneal transplantation.

[1] Wollensak G, Aurich H, Pham D & Wirbelauer C. Hydration behaviour of porcine cornea crosslinked with riboflavin and ultraviolet A. J Cataract Refract Surg 2007; 33: 516–521.

[2] Gadelha D. et al. [Therapeutic effect of corneal cross-linking on symptomatic bullous keratopathy] Article in Portuguese. Arq Bras Oftalmol 2009; 72: 462–466.

[3] Gharaee H. et al. The effects of riboflavin/Ultraviolet-A corneal cross-linking on the signs and symptoms of Bullous keratopathy. Middle East Afr J Ophthalmol 2011; 18: 58–60.

[4] Hafezi F. et al. Modified corneal collagen crosslinking reduces corneal oedema and diurnal visual fluctuations in Fuchs dystrophy. Br J Ophthalmol 2010; 94: 660–661.

[5] Khan, M. et al. Corneal collagen cross linking (CXL) in treatment of pseudophakic bullous keratopathy. Pak J Med Sci 2016; 32:965-968.

[6] Wollensak G. et al. Potential use of riboflavin/UVA cross-linking in bullous keratopathy. Ophthalmic Res 2009; 41: 114–117.