The prevalence of keratoconus in northern Poland: A cross-sectional study of patients from a primary healthcare practice

Introduction: Keratoconus is defined as central and/or paracentral corneal thinning and steepening with conse-quent 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 Elblag 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 (& kappa;) 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 & PLUSMN; 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 (& kappa; = 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.