Estimation of patient visit rate and incidence of keratoconus in the 23 wards of Tokyo

PURPOSE: To estimate the patient visit rate and the incidence of keratoconus in the 23 Wards of Tokyo. SUBJECTS AND METHODS: We searched for keratoconus patients with questionnaires sent to 141 hospitals in the 23 Wards of Tokyo. The patient visit rate was estimated using the number of patients from 15 to 44 years old. The incidence was estimated from the number of patients in whom the onset of the disease was at the age 15 to 34. RESULTS: Three hundred and twenty-five patients (205 males and 120 females) were found during a survey of three months. The return rate of the questionnaires was 49.6%. Male/female ratio was 1.7/1.0. The patient visit rate of keratoconus during three months was estimated to be 12.4 x 10(-5) (1/8,100) in males and 6.7 x 10(-5) (1/15,000) in females. The annual incidence was estimated to be 12.1 x 10(-5) (1/8,300) in males and 5.6 x 10(-5) (1/17,900) in females. 6.5% of the patients were given corneal transplants. CONCLUSION: We estimated the patient visit rate and the incidence of keratoconus on the basis of the survey of hospitals of the 23 Wards of Tokyo during a 3-month period. Compared with the previous reports, our data suggests that the proportion of women is increasing in patients with keratoconus, and that the ratio of patients who have to receive corneal transplant therapy are decreasing. A large-scale epidemiological study is required.