title: Distribution and heritability of intraocular pressure in chinese children: the Guangzhou twin eye study.
abstract: OBJECTIVE
  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.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, People's Republic of China.
authors.forename: Yingfeng
authors.initials: Y
authors.lastname: Zheng
authors.forename: Fan
authors.initials: F
authors.lastname: Xiang
authors.forename: Wenyong
authors.initials: W
authors.lastname: Huang
authors.forename: Guofu
authors.initials: G
authors.lastname: Huang
authors.forename: Qiuxia
authors.initials: Q
authors.lastname: Yin
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D044466:Asian People / Q000235:genetics*; D002648:Child; D002681:China / Q000453:epidemiology; D005260:Female; D005838:Genotype; D006801:Humans; D007429:Intraocular Pressure / Q000235:genetics*; D008297:Male; D019655:Quantitative Trait, Heritable; D012042:Registries; D017678:Sex Distribution; D014065:Tonometry, Ocular; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic