Influence of ethnic origin on the incidence of keratoconus and associated atopic disease in Asians and white patients.

PURPOSE: To investigate the influence of ethnic origin on the incidence of keratoconus and the association of atopic diseases in patients with keratoconus.

METHODS: Retrospective study of new patients referred to Dewsbury District General Hospital and diagnosed with keratoconus in a 6-year period between 1994 and 2000. The ethnic origin of the patient was defined as white, Asian, or other. Incidence was calculated from the catchment population of 176 774 (82% white people, 17% Asians, 1% others). t-Test, confidence intervals and chi2 tests were used to show statistical significance.

RESULTS: A total of 74 cases of keratoconus were diagnosed over this period. Of these patients 29 (39%) were white and 45 (61%) were Asian. This equated to an incidence of keratoconus of 25 per 100 000 (1 in 4000) per year for Asians, compared with 3.3 per 100 000 (1 in 30 000) per year for white people (P<0.001). Asians presented significantly younger than white patients. The incidence of atopic disease was found to be significantly higher in white compared to Asian keratoconic patients.

CONCLUSIONS: Asians were significantly more likely to present with keratoconus. The Asian patients were mostly of Northern Pakistani origin. This community has a tradition of consanguineous, especially first-cousin marriages. The higher incidence in this population was highly suggestive of a genetic factor being significant in the aetiology. The incidence was higher than revealed by previous studies. Atopic disease was significantly less common in Asians compared to white people, supporting the theory of a different aetiology in these patients.