Keratoconus is a progressive corneal condition that typically affects young patients' vision although a less common variant, pellucid marginal degeneration (PMD), occurs in older patients. Often with an onset in teenage years, it results in a progressive bulging forward of the cornea into a cone-like shape. With an incidence of 1:2000 people, until recently progression of the disease could not be prevented or stabilised. In recent years Corneal Cross Linking (CXL) has become available which offers stabilisation of the disease.
Untreated, the natural history of keratoconus is to progress. Eventually the disease stabilises but frequently only after significant visual distortion results. This can make wearing glasses very difficult and result in unsatisfactory quality of vision. When vision is poor with glasses, rigid contact lenses are the mainstay of treatment. This too may not provide sufficient clarity and can have their own issues in terms of comfort and safety. When contact lenses fail the only option until the advent of Corneal Cross Linking has been corneal grafting.