Keratoconus Prevalence in Families: A French Study

Purpose: To assess the keratoconus (KC) prevalence among first-degree relatives of affected subjects. Methods: We performed large epidemiological, prospective, and observational cohort, which took place in the French KC National Reference Centre, in Bordeaux. We studied data from 94 unrelated patients with KC and at least 2 first-degree relatives assessable. Each subject had a thorough ocular examination including visual acuity, refraction, slitlamp biomicroscopy, indirect ophthalmoscopy, keratometry, corneal topography and tomographer (Topographic Modeling System; Tomey Corporation, Japan; and Galilei G4, Ziemer, Switzerland, respectively), pachymetry, and biomechanical properties of cornea (Ocular Response Analyzer; Reichert, Depew, NY). Additional data were collected about atopy, smoking, and eye-rubbing habits. KC prevalence, multivariate analysis, and familial correlation analysis have been studied. Results: Of the 221 relatives, 9.05% (n = 20) had clinically manifest KC, and 15.4% (n = 31) had subclinical KC. The prevalence of KC was estimated equal to 0.14 [95% confidence interval (CI), 0.07-0.22] among parents, 0.03 (95% CI, 0-0.10) among offspring, and 0.10 (95% CI, 0.04-0.20) among siblings. In multivariable analysis, age and eyerubbing were associated with an increased risk of KC. The familial correlation of KC among probands' first-degree relatives was estimated at 0.55 among parents, 0.29 among offspring, and 0.49 among siblings. Conclusions: Being a first-degree relative of a subject with KC remains a risk factor for developing KC. This should be taken into account especially when screening for KC in pediatric patients, for refractive surgery candidates, and for patients being evaluated for cataract surgery.