collagen cross - linking for Pellucid Marginal degeneration

Pellucid marginal degeneration (PMD) is a rare progressive condition resulting in inferior corneal thinning and astigmatism. Alongside keratoconus and keratoglobus, it is considered one of noninflammatory corneal ectasias. The focus of corneal thinning is greatest inferiorly resulting in diminished visual acuity and overall reduction in visual quality. Traditional methods of treatment or disease management have been similar to those proposed for keratoconus, contact lenses, escalating to intrastromal rings, lamellar keratoplasty or penetrating keratoplasty. Collagen cross-linking (CXL) has steadily gained acceptance as the treatment of choice for progressive corneal ectasias. Although it has been described at length for keratoconus, there is little literature describing or advocating its use in PMD. In this article, we will review the evidence for CXL and its use in PMD.