The prevalence of keratoconus in northern Poland: A cross-sectional study of patients from a primary healthcare practice
Piotr Kanclerz, Katarzyna Przewłócka, İbrahim Toprak, Jorge L. Alió
Abstract
INTRODUCTION: Keratoconus is defined as central and/or paracentral corneal thinning and steepening with consequent irregular astigmatism. To date, no prospective study has reported its prevalence in Central Europe. This study aimed to evaluate the prevalence of keratoconus assessed with Scheimpflug imaging in a profile of general medicine practice in Poland. METHODS: This cross-sectional study collected data by inviting all patients aged 10-80 years subscribed to a single general practitioner in the Elbląg area, Poland. Corneal measurements were performed using a rotating Scheimpflug corneal tomography system. Three masked examiners established the diagnosis of keratoconus in the right or left eye. Fleiss' kappa coefficient (κ) was used to qualitatively analyze the interexaminer agreement. RESULTS: Of 1,705 patients invited to the study, 771 agreed to participate (45.2%). The mean age of the 728 patients (60.6% female and 39.4% male) with gradable images in at least one eye was 53.6 ± 16.5 years. All of the examiners classified the same four cases as keratoconus (0.549%, 549 per 100,000, 95% confidence interval 150 to 1,400 per 100,000), of which two were bilateral. Fleiss' kappa showed almost perfect agreement among the three examiners regarding the diagnostic decision (κ = 0.784, 95% confidence interval 0.750 to 0.817, p < 0.001). The keratoconus cases were all women (p = 0.106), aged 48, 69, 70, and 71 years old. CONCLUSION: The prevalence of keratoconus in this area was higher than that previously demonstrated in many European countries. Underestimation of the prevalence has been postulated but never demonstrated.