Epidemiology of Keratoconus

Abstract

The burden of a disease is determined by its incidence and prevalence, which in turn inform the provision of relevant healthcare services including screening programmes, primary and specialist medical care. Genetic and environmental factors affect the incidence and prevalence of keratoconus and it has become apparent that previous estimates of prevalence have been overly conservative, as new diagnostic modalities have enabled earlier detection of corneal changes and also the diagnosis of sub-clinical, or `forme fruste' disease. This latter classification has proved important in the field of keratorefractive surgery, where preoperative assessment has identified previously undiagnosed, sub-clinical keratoconus and thus protected patients from iatrogenic worsening of ectasia. Furthermore, cases previously thought to be unilateral have frequently been shown with modern imaging to be bilateral, with one eye at an earlier sub-clinical stage. It is now accepted that truly unilateral keratoconus does not exist, although it may present unilaterally in the context of asymmetric environmental factors, such as eye rubbing. Improved knowledge of the epidemiology of keratoconus has increased our understanding of the underlying pathogenesis, and earlier recognition of subclinical keratoconus has contributed to a surge in new management strategies designed to ameliorate the long-term burden of disease.