Epithelium-on Cross-linking Versus Observation of Fellow Eyes of Patients With Unilateral Clinically Evident Keratoconus

Keratoconus (KC) is a bilateral asymmetric progressive corneal degenerative disease associated with corneal thinning and protrusion with resultant irregular astigmatism and visual loss. Although several studies showed that epithelium-off corneal cross-linking (epi-off CXL) is more effective in preventing KC progression compared with epithelium-on corneal cross-linking (epi-on CXL), the removal of corneal epithelium in epi-off CXL might be associated with a number of serious complications such as persistent epithelial defects and sight-threatening infectious keratitis. Additionally, recent systematic reviews and meta-analysis concluded that epi-on CXL is as effective as epi-off CXL in terms of visual and topographic stability of keratoconus, but has the advantage of being much safer avoiding the complications of epithelial removal. The management of the better eye, of young patients with unilateral clinically evident KC, is controversial. Some ophthalmologists prefer to cross-link the better eye, while others prefer to conservatively follow it up, in order to avoid complications of epithelial removal in epi-off CXL.