A Specular Microscopic Study of Corneal Endothelium After Accelerated Corneal Collagen Cross Linking

Keratoconus (KC) is a progressive, non-inflammatory corneal degenerative disease. It is a pathology characterized by a progressive thinning and protrusion of the cornea that ends in a cone-shaped cornea. This results in progressive myopia and irregular astigmatism with associated progressive loss of vision and thus reduced quality of life.Collagen cross-linking (CXL) is a relatively new conservative approach for progressive corneal ectasia. The main indication for CXL is to slow the progression of corneal ectatic diseases, such as keratoconus, pellucid marginal degeneration (PMD), keratoglobus and iatrogenic ectasia.The basic principle of this method is the chemical interaction of ultraviolet A radiation (315-400nm ) and riboflavin to induce covalent bond formation between collagen fibers of the cornea. In this way, the stiffness and rigidity of the cornea are provided.Corneal collagen cross-linking (CXL) was first introduced by Wollensak with an ultraviolet-A (UVA) protocol of 3 medium wave mW/cm2 intensity at 370 nm over an exposure time of 30 minutes (now termed the "Dresden protocol"). Researchers have proposed accelerated CXL (ACXL) protocols, to improve convenience and comfort for patients. These ACXL protocols have the aim of decreasing UVA exposure time by increasing UVA fluency to achieve the same overall total UVA dosage.Despite corneal CXL is a safe and effective procedure with few known side effects .Persistent corneal edema and possible endothelial cell damage have been reported in a few cases after CXL. Based on the extent of endothelial damage, patients may require penetrating keratoplasty.