Keratoconus detection by novel indices in patients with Down syndrome: a cohort population-based study

Purpose To use novel indices to determine the prevalence of KC and its progression in patients aged 10-30 years with Down syndrome. Study design Cohort population-based study. Methods Two hundred twenty-six of 250 invited Down syndrome patients were enrolled. The diagnostic criteria were confirmed by two independent expert examiners using slit-lamp examinations and topographic indices measured by Pentacam HR (Oculus Optikgerate): maximum keratometry centered on the steepest point (zonal Kmax-3 mm), Ambrosio's relational thickness (ART), inferior-superior asymmetry (IS-value), Belin/Ambrosio deviation value (BAD-D), the Tomographic and Biomechanical Index (TBI), and a posterior elevation map. In the KC cases, Corvis ST (Oculus Optikgerate) was done. All the KC cases completed the second phase in 2017. Results KC was identified in 28 patients (12.39%; 95% confidence interval: 8.2-17.9%): 20 bilateral and eight unilateral cases. Of these, 24 were in the <= 20-years age group, and four, in the > 20-years age group. The frequency of KC was not significantly correlated with age (P = 0.804) or gender (P = 0.322). In the KC cases, the mean zonal Kmax-3 mm, ART-max, IS-value, BAD-D, CBI, and TBI were 50.40 +/- 5.88 D, 321.63 +/- 111.94 mu m, 1.99 +/- 2.51, 3.73 +/- 3.12, 0.54 +/- 0.61, and 0.86 +/- 0.20, respectively, and the minimum corneal thickness was 492.17 +/- 42.67 mu m. Of the 28 patients, 39.6% showed progression, and all were in the <= 20-years age group. Conclusion The prevalence of KC in Down syndrome patients is significantly higher than that reported in non-Down syndrome individuals of the same age groups. The progression rate is approximately similar to that of the non-Down syndrome population. Screening programs should be applied to prohibit serious visual impairment in these populations.