Purpose To explore if genetic factor make effect on determination of sighting dominance in a classic twin study.
Methods Twins aged 7 to 19 years enrolled from the Guangzhou Twin Registry received comprehensive eye examination. Hole-in-the-card test was conducted by two trained optometrists under the same rule to determine the dominant eye. Zygosity was confirmed by genotyping in all same-sex twin pairs. Main results were analyzed using probandwise concordance rate.
Results Of those recruited, 1051 twin pairs were identified in the analysis, including 669 monozygotic (MZ) and 382 dizygotic (DZ) pairs. Right dominant eye presented in 57.5% and left dominant eye presented in 41.6% participants, the other 0.9% showed no eye preference. The intraclass agreement was 51.57% in MZ and 52.88% in DZ. Kappa value was extremely low, that is 0.01 in MZ twins and 0.029 in DZ twin pairs respectively. Due to the lower concordance in MZ twins than that of DZ twins, special software (Mx) failed to calculate to heritability.
Conclusions Environmental elements might be the main determinative factor of the sighting dominance.