Distribution and Heritability of Intraocular Pressure in Chinese Children: The Guangzhou Twin Eye Study

PURPOSE. To assess the distribution and heritability of intraocular pressure (IOP) in Chinese children. METHODS. Twins aged 8 to 16 years were recruited from the Guangzhou Twin Registry. IOP was measured in each twin and co-twin together, with a handheld tonometer by the same operator. Zygosity was determined based on genotyping with 16 polymorphic markers in all same-sex twin pairs. Heritability was estimated with a univariate variance component model. RESULTS. Four hundred seventy-three twin pairs (309 monozygotic [MZ] and 164 dizygotic [DZ] twins) were available for data analyses. The mean IOP was 14.2 (SD 2.3) mm Hg. Neither age nor sex was correlated with IOP. Phenotypic correlation was 0.68 (95% confidence interval [CI], 0.62-0.74) in MZ twins and 0.40 (95% CI, 0.26-0.52) in DZ twins. A genetic model involving additive genetic and unique environmental effects was the best fit. Heritability was estimated as 66.5% ( 95% CI, 60.6%-71.6%). CONCLUSIONS. IOP is not correlated with age and sex in young children. Similar to the European population, the variation of IOP in healthy Chinese children is mainly attributable to additive genetic effects. (Invest Ophthalmol Vis Sci. 2009;50:2040-2043) DOI:10.1167/iovs.08-3082