Publication Exclusive: Contact lens-assisted cross-linking treats corneal ectatic disorders in thin corneas

Collagen fibers in the human body are normally bonded together and stabilized by covalent cross-links. The tensile strength of mature collagen fibers is largely due to intermolecular covalent cross-links. Collagen cross-linking was described by Theo Seiler et al as a means to strengthen a weak and ectatic cornea. This works by utilizing ultraviolet A at a wavelength of 370 nm in the presence of the photosensitizer riboflavin to create an increased number of covalent bonds among corneal stromal collagen fibers.Riboflavin is a photosensitizer and causes damage at a lower UVA irradiance level of 0.36 mW/cm2. The creation of oxygen free radicals leads to induction of collagen cross-links, which in turn leads to more compact interlamellar connections. Riboflavin also has an additional protective role by increasing the absorption coefficient, thereby decreasing final irradiance at the endothelial level down to 0.18 mW/cm2. However, 400 µm of riboflavin-saturated stroma above the endothelium is considered safe to avoid adverse effects. In patients with corneas thinner than this, conventional cross-linking cannot be performed. For patients with corneal stromal thickness between 350 µm to 400 µm after epithelial removal, we have performed a new technique called contact lens-assisted cross-linking (CACXL). This was described by Soosan Jacob.