The heritability of corneal hysteresis and ocular pulse amplitude: a twin study.

PURPOSE To examine the roles of genetic and environmental factors in corneal hysteresis and ocular pulse amplitude by performing a classic twin study. DESIGN Cross-sectional twin study. PARTICIPANTS AND/OR CONTROLS Two hundred sixty-four twin pairs: 135 monozygotic (MZ) and 129 dizygotic (DZ). METHODS Corneal hysteresis was measured using the Reichert Ocular Response Analyzer (ORA; Reichert, Buffalo, NY), and ocular pulse amplitude was measured using the Pascal Dynamic Contour Tonometer (DCT; Swiss Microtechnology AG, Port, Switzerland). MAIN OUTCOME MEASURES Contribution of genetic and environmental effects on corneal hysteresis and OPA among MZ and DZ twins. RESULTS The mean corneal hysteresis was 10.24+/-1.54 mmHg and the mean ocular pulse amplitude was 2.88+/-0.97 mmHg. The MZ correlations were higher than DZ for both corneal hysteresis and ocular pulse amplitude (correlation coefficients, 0.75:0.42 and 0.59:0.32 for MZ:DZ twins, respectively). Modeling suggested heritability of corneal hysteresis of 0.77 (95% confidence interval [CI], 0.70-0.82), with the remaining proportion of variance because of individual environmental effects of 0.23 (95% CI, 0.18-0.30). For ocular pulse amplitude, the heritability was 0.62 (95% CI, 0.51-0.70), with the remaining proportion of variance the result of individual environmental effects of 0.38 (95% CI, 0.30-0.49). CONCLUSIONS This study demonstrated that additive genetic influences explained most of the individual differences in corneal hysteresis and ocular pulse amplitude among these twins.