Corneal cross-linking with riboflavin for keratoconus

Keratoconus (KC) is a degenerative disorder of the eye in which cornea becomes progressively thinner and bows outward into a more conical shape than its normal gradual curve. KC affects approximately 0.05% of the global population. Patients with KC often experience eye irritation, headaches, light halos, light sensitivity, worsening myopia, and impaired quality of life. KC is usually diagnosed in the adolescent period. Various treatment options for KC include simple correction with glasses, soft or rigid gas permeable contact lenses, surgical implantation of intrastromal corneal ring segments (Intacs), and corneal transplant. In addition, corneal-crosslinking with riboflavin and ultraviolet A (CXL) is increasingly considered as a method for managing KC. The treatment objective for CXL is to stabilize the underlying disease process by strengthening the stromal collagen network in order to delay or defer the need for corneal transplant. In the process of CXL, riboflavin (vitamin B2) works as a photo-mediator to increase the absorption of ultraviolet A light into the corneal stroma. The ultraviolet A (UVA: 370 nm) light increases the degree of molecular bonds of the extracellular matrix of the cornea. Therefore, CXL slows or even stops the progression of KC by increasing the strength and rigidity of the cornea. CXL can be performed with or without removing corneal epithelium. Common reported side-effects of CXL are blurry vision, lacrimation and the sensation of a foreign body for approximately 24 to 48 hours. Serious side effects include corneal haze and keratitis. CXL is only indicated for patients with corneas greater than 400 mcm thick. Corneal cross-linking with riboflavin -- UVA for keratoconus has been increasingly used in some Canadian jurisdictions. However it is currently not covered by any Canadian jurisdiction. Demand for CXL as the standard of care for keratoconus is increasing in some Canadian jurisdictions, although the long-term effectiveness and CXL's impact on the need for corneal transplant is unk