title: No Evidence for Genetic Contribution of Ocular Dominance: The Guangzhou Twin Eye Study.
abstract: OBJECTIVE
  The purpose of this study was to explore the heritability of ocular dominance in a classic twin study.
  
  
  METHODS
  A classical twin study.
  
  
  METHODS
  Twins aged 7 to 19 years enrolled from the Guangzhou Twin Registry received comprehensive eye examinations. Ocular dominance was assessed by the "hole-in-the-card test" by trained optometrists. Zygosity of the participants was confirmed by genotyping in all same-sex twin pairs. The pairwise concordance rate was calculated as the main outcome.
  
  
  RESULTS
  After excluding 110 children with anisometropia of 2.0 diopters or greater and 24 children with alternating ocular dominance, a total of 941 twin pairs were identified in the analysis, including 596 monozygotic and 345 dizygotic pairs. Right-eye dominance was present in 59.3% of twins with available data. The pairwise concordance rate was 0.529 and 0.530 in monozygotic and dizygotic twin pairs, respectively (P > 0.5). The tetrachoric correlation was 0.043 and 0.035, respectively. When comparing the young twins and their parents, no significant difference in the percentage of offspring with left-eye dominance was found between right × right parent mating group and non-right × right parent mating groups.
  
  
  CONCLUSIONS
  Genetic factors may not be involved in ocular dominance in Chinese teens and children.
authors.affiliation: From the State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Xixi
authors.initials: X
authors.lastname: Yan
authors.forename: Nathan
authors.initials: N
authors.lastname: Congdon
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Qianyun
authors.initials: Q
authors.lastname: Chen
authors.forename: Xinxing
authors.initials: X
authors.lastname: Guo
authors.forename: Mingguang
authors.initials: M
authors.lastname: He