title: Contribution of genetic and environmental effects on lens thickness: the Guangzhou Twin Eye study.
abstract: OBJECTIVE
  This study investigated the heritability of lens thickness (LT) and relative lens thickness (LT/axial length, rLT) measured by Lenstar among Chinese children and adolescents in the Guangzhou Twin Eye study.
  
  
  METHODS
  Twins aged 8 to 22 years were enrolled from the Guangzhou Twin Registry. A series of LT and axial length (AL) measurements using the Lenstar were taken for each twin. Zygosity was confirmed by genotyping in all same-sex twin pairs. Heritability was assessed by structural variance component genetic modeling, after adjustment for age and sex with the Mx program.
  
  
  RESULTS
  Seven hundred sixty-eight twin pairs (482 monozygotic [MZ] and 286 dizygotic [DZ] twins) were available for data analysis. The mean (standard deviation) LT and rLT were 3.45 (0.18) mm and 0.142 (0.01), respectively. The intraclass correlation coefficients (ICCs) for LT were 0.90 for the MZ and 0.39 for the DZ twins; and those for rLT were 0.90 for the MZ and 0.40 for the DZ twins, respectively. The best-fitting model yielded 89.5% (95% CI: 87.8%-91.0%) of additive genetic effects and 10.5% (95% CI: 9.0%-12.2%) of unique environmental effects for LT, and 89.3% (95% CI: 89.2%-89.3%) of additive genetic effects and 10.7% (95% CI: 10.7%-11.4%) of unique environmental effects for rLT.
  
  
  CONCLUSIONS
  This study confirms that the LT in young healthy subjects may be mainly affected by additive genetic factors. High heritability remains even when the data are corrected for the influence of AL with the use of rLT.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Peiyang
authors.initials: P
authors.lastname: Shen
authors.forename: Xiaohu
authors.initials: X
authors.lastname: Ding
authors.forename: Yingfeng
authors.initials: Y
authors.lastname: Zheng
authors.forename: Nathan G
authors.initials: NG
authors.lastname: Congdon
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
mesh_terms: D000293:Adolescent; D044466:Asian People / Q000235:genetics*; D002648:Child; D005260:Female; D005838:Genotype; D006801:Humans; D007908:Lens, Crystalline / Q000033:anatomy & histology*; D008297:Male; D008957:Models, Genetic; D009929:Organ Size / Q000235:genetics*; D010641:Phenotype; D019655:Quantitative Trait, Heritable; D012042:Registries; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*; D055815:Young Adult