Purpose: To explore the heritability of ocular dominance in a classic 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 ≥ 2.0 D and 24 children with alternating ocular dominance, a total of 941 twin pairs were identified in the analysis, including 596 monozygotic (MZ) and 345 dizygotic (DZ) 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 MZ and DZ twin pairs respectively (P>0.5). The tetrachoric correlation was 0.043 and 0.035 respectively. 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 involved in ocular dominance as assessed by the hole in-the-card test in Chinese teens and children.