Comparison of the Efficacy of Standard
Epithelium-off Corneal Collagen Cross-linking
and Iontophoresis-assisted Transepithelial
Corneal-collagen Cross-linking in the Treatment
of Keratoconus: A Systematic Review

Madeleine Tillyer BAppSc MOrth

Discipline of Orthoptics, School of Allied Health, Human Services and Sport, La Trobe University, Melbourne, Australia

Purpose: Keratoconus is an ectatic corneal condition characterised by progressive thinning and steepening of the cornea. Corneal collagen cross-linking (CXL) is a treatment aimed at halting keratoconus progression by increasing corneal rigidity. Of the various techniques, epithelium-off (S-CXL) is the current gold standard. Epithelium-on methods are favourable as the intact epithelium reduces pain and risk of infection, however riboflavin permeability is reduced. Iontophoresis-assisted transepithelial CXL (I-CXL) was developed to overcome this. This systematic review compares the efficacy of I-CXL against S-CXL at halting keratoconus progression to determine if I-CXL could become the new gold standard. 

Methods: A search was performed across Medline, Embase and CINAHL, alongside citation searching, and hand searching of the Australian Orthoptic Journal. Studies comparing I-CXL with S-CXL were included. Critical appraisal and data extraction were performed to conduct a narrative synthesis. 

Results: Seven studies of 378 were deemed eligible for inclusion. All studies found I-CXL to be a safe technique for stabilising keratoconus progression,  roducing results that were either comparable or inferior to S-CXL results. However, no definitive conclusion can be drawn regarding the efficacy of I-CXL  against S-CXL due to the limited number of studies included, their small sample sizes and the influence of bias.