Objective: This study aims to investigate the correlation of dominant eye and refractive error between monozygotic twins.
Methods: The data of dominant eye and refractive error of 13 pairs of monozygotic twins who were treated at the Optometry Clinic were collected. The paired chi-square test and Kappa consistency test were used to analyze the data of dominant eye between monozygotic twins, while the paired t  test and Pearson correlation analysis were adopted to analyze the refractive error data. SPSS version 22.0 software was used to analyze the above statistics.
Results: In the Kappa consistency test of dominant eye between monozygotic twins, Kappa value = 0.451, p = 0.052, p> 0.05, and in the paired chi-square test, p = 0.250. In the spherical equivalent paired t test for the right eye of monozygotic twins, t = 1.491 and p = 0.162, while in the spherical equivalent paired t test for the left eye, t = 0.753 and p = 0.466. In the spherical equivalent correlation analysis of monozygotic twins, for the spherical equivalent refraction of the right eye, the Pearson correlation results were r = 0.901 and p = 0.00, and for the spherical equivalent refraction of the left eye, the Pearson correlation results were r = 0.971 and p = 0.00.
Conclusion: The difference in the chi-square test of dominant eye is not statistically significant between monozygotic twins, but dominant eye and refractive error are correlated to some extent. It is suggested that heredity may be the main determinant of the dominant eye. There is no difference in refractive error between identical twins which are highly correlated, however.
Keywords: refractive error, dominant eye, monozygotic twins/identical twins, heredity, genes