MODIFIED PROTOCOL FOR THE TREATMENT OF THIN CORNEAS

In order to overcome the contra-indication of treating corneas with a thickness bordering on 400μm,  Kymionis et al. [1] developed the use of pachymetry-guided epithelial debridement- a treatment modification in which the epithelium is only removed from regions of the cornea with a thickness in excess of 400μm. The safety and efficacy of the treatment has yet to be fully validated,

An alternative solution proposed by Hafezi et al. [2] is the replacement of the standard iso-osmolar riboflavin solution (containing dextran) with a hypo-osmolar riboflavin solution (without dextran) in order to swell the cornea to an acceptable thickness prior to cross-linking. Treatment of 20 patients with thin corneas (minimum preoperative stromal thickness of 323µm) using this method resulted in keratoconus progression being arrested in all cases [2]. It is however advised that a minimal preoperative stromal thickness of 330μm is required for successful cross-linking using this modified protocol [3].

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

[2] 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.

[3] Hafezi, F. Limitation of collagen cross-linking with hypoosmolar riboflavin solution: failure in an extremely thin cornea. Cornea. 2011;30(8):917-9.