In order to overcome the contra-indication of crosslinking corneas with a thickness bordering on 400μm, a number of treatment modifications have been proposed for the treatment of very thin corneas. These include the use of hypo-osmolar riboflavin solutions to swell the cornea to reach the optimum tissue thickness for cross-linking [1]; the use of transepithelial riboflavin solutions [2] and/or iontophoresis-assisted riboflavin delivery [3] to avoid the requirement for removal of the epithelium and maximise the thickness of the tissue; the use of higher riboflavin concentrations to protect the corneal endothelium by reducing the amount of UVA radiation reaching the deeper layers of the tissue [4]; the use of pachymetry-guided epithelial debridement (‘epithelial island technique’) to selectively remove the epithelium from regions of the cornea with a thickness >400 µm [5]; the use of a shielding riboflavin-soaked contact lens (‘contact lens-assisted cross-linking’) [6]; and the use of additional corneal tissue (refractive lenticules) spread over the cornea to thicken the thinnest parts of the tissue prior to cross-linking (‘lenticule assisted cross-linking’) [7].

[1] Hafezi, F. et al. Collagen crosslinking with ultraviolet A and hypoosmolar riboflavin solution in thin corneas. Journal of Cataract and Refractive Surgery. 2009;35:621-4.

[2] Spadea, L, et al. Transepithelial corneal collagen cross-linking in ultrathin keratoconic corneas. Clin Ophthalmol 2012; 6: 1785-1792

[3] Bikbova, G. et al. Standard corneal collagen crosslinking versus transepithelial iontophoresis-assisted corneal crosslinking, 24 months follow-up: randomized control trial.  Acta Ophthalmol 2016; 94: e600-e606

[4] O’Brart, NAL. et al An investigation of the effects of riboflavin concentration on the efficacy of corneal cross-linking using an enzymatic resistance model in porcine corneas. Invest Ophthalmol Vis Sci 2018; 59: 1058–1065

[5] Kymionis, G. et al. Customized pachymetric guided epithelial debridement for corneal collagen cross linking. BMC Ophthalmology. 2009;9:10.

[6] Knyazer, B. et al Corneal cross-linking in thin corneas: 1-year results of accelerated contact lens-assisted treatment of keratoconus. J Refract Surg 2019; 35: 642–648.

[7] Sachdev, MS. et al Tailored stromal expansion with a refractive lenticule for crosslinking the ultrathin cornea. J Cataract Refract Surg 2015; 41: 918–923.

Last updated: December 2021