High heritability of posterior corneal tomography, as measured by Scheimpflug imaging, in a twin study

Purpose: Anterior corneal curvature shows significant heritability. Scheimpflug imaging also permits assessment of posterior tomography. We estimated heritability of posterior and anterior tomographic parameters. Methods: Oculus Pentacam (Oculus, Wetzlar, Germany) images were obtained in twins from the TwinsUK cohort. Mean anterior and posterior radii of curvature (right cornea) were compared within twin pairs, and heritability calculated (maximum likelihood structural equation modelling, using OpenMx package). Heritability estimates were also calculated for other parameters (anterior and posterior elevation at apex and thinnest point; pachymetry at apex and thinnest point; average pachymetry progression index). Results: Images from 138 twins were included (32 MZ and 37 DZ twin pairs). Mean (SD) age was 61 (11) years; 91% were female. Coefficients for intra-pair correlation for MZ and DZ twins were, respectively, 0.89 and 0.42 for anterior curvature, and 0.93 and 0.46 for posterior curvature (p ≤ 0.0001 for differences between MZ and DZ correlations; Fisher r-to-z transformation). Heritability estimates (95% CI) for anterior and posterior curvature were 89% (79 - 93%) and 90% (83 - 94%) respectively. Estimates for all other parameters were ≥75%, except anterior apical elevation (61%). Point estimates for posterior parameters were consistently higher than anterior parameters, although confidence intervals overlapped. Age-matching yielded similar estimates. Inter-eye correlations were high; correlations with age were weak (r<0.30). Conclusions: This is the first study to explore heritability of a number of different parameters of corneal tomography, including posterior curvature. Almost all parameters appeared highly heritable, with a trend towards higher heritability estimates for posterior parameters.