Incidence and prevalence of keratoconus in Denmark – an update

Abstract

Purpose: To describe the annual incidence rate of keratoconus in Denmark 1995–2015 and prevalence of keratoconus in the National Danish Patient Register 1977–2015. Methods: All patients diagnosed with keratoconus in the National Danish Patient Register 1977–2015 were included in the study. The annual incidence rates and the overall prevalence of diagnosed keratoconus in the register were calculated using life tables from the general Danish population. A sub-analysis excluding immigrants and descendants was performed. Results: An increase in the annual incidence rate was seen from 1.24 per 100 000 person-years in 2003 to 3.83 per 100 000 in 2011. The average incidence rate 2011–2015 was 3.60 per 100 000 person-years. A survey of primary-sector ophthalmologists supported that the register data could be considered complete from 2011. The prevalence of diagnosed keratoconus in the National Patient Register 1977–2015 was 44 per 100 000 persons. Excluding immigrants and descendants yielded an average incidence rate 2011–2015 of 2.89 per 100 000 person-years and a prevalence of diagnosed keratoconus in the National Patient Register 1977–2015 of 40 per 100 000 persons. Conclusion: The present incidence rate (based on 2011–2015 data) has increased 2–3-fold during the last 10–15 years. The increase is possibly largely a consequence of more complete data due to the availability of corneal cross-linking, which has changed the referral pattern from the primary sector. Other factors such as better diagnostic tools and immigration may also play a role.