High heritability of central corneal thickness : the twins eye studies

PURPOSE: A classical twin study was performed to determine the heritability of central corneal thickness, an important parameter in glaucoma assessment. METHODS: The concordance of CCT between monozygotic (MZ) and dizygotic (DZ) twins was compared. A total of 256 twin pairs (131 MZ and 125 DZ) were recruited from 3 centers: the Twin Eye Study in Tasmania, the Brisbane Adolescent Twin Study and the Twins UK adult registry held at St. Thomas' Hospital in London. As part of an extensive ophthalmic evaluation, CCT was measured using ultrasound pachymetry. Structural equation modelling using the Mx program was used to determine the heritability of CCT. RESULTS: The mean age of subjects was 38 years (range 8-81). The mean CCT of all eyes examined was 544.5˜í¬¿m (standard deviation [SD] 37.3). The CCT measurements were more highly correlated in MZ twins than in DZ twins, with intraclass correlation coefficients of 0.95 and 0.52, respectively, suggesting a strong genetic influence. A model of additive genetic and unique environmental effects provided the best fit, yielding a heritability of 0.95 (95% Cl 0.93-0.96) with the remaining variation being attributable to unique environmental factors. CONCLUSION: In this study of Australian and United Kingdom twins, we found that genetic factors are of major importance in CCT, with a heritability of 0.95.