Topographic Keratoconus is not Rare in an Iranian population: The Tehran Eye Study

Purpose: To determine the prevalence of topographic keratoconus in an Iranian population, selected from Tehran districts 1 to 4. Methods: In a cross-sectional study, samples were selected from four districts of Tehran through stratified cluster sampling. Participants underwent ophthalmic and optometric examinations and Orbscan topography maps were acquired from 442 people. Based on Orbscan topography maps, cases of keratoconus were categorized. Results: In the study sample, 263 people (61.7%) were female, and the participants' mean age was 40.8 +/- 17.1 years (range 14-81 years). Age-and sex-standardized prevalence of keratoconus was 3.3% (95% confidence interval, CI, 0.1-5.5%. The standardized prevalence of bilateral keratoconus was 1.8% (95% CI 0.2-3.5). The age-standardized prevalence of keratoconus was 3.9% and 2.6% in men and women, respectively (p = 0.341). The prevalence of keratoconus was 0.8% in the 14-29-year-old age group and 7.5% in those >= 60 years; the prevalence of keratoconus significantly increased with age (odds ratio, OR, 1.05, 95% CI 1.01-1.08). The prevalence of keratoconus was 2.5% (95% CI 0.5-4.6) in the Persian ethnic group and 7.9% (95% CI 1.6-15.7) among non-Persians (p = 0.063 and OR 3.33). Conclusions: This study provides the first population-based estimate of the prevalence of keratoconus in Iran. The prevalence of topographic keratoconus was high among citizens of Tehran districts 1 to 4. To confirm the hypothesis of a high rate of keratoconus in Iran, more extensive studies are needed which would examine the role of genetics and the environment.