Astigmatism and myopia are two common ocular refractive errors that can impact daily life, including student learning and productivity. Current understanding suggests that the etiology of these conditions is the result of a complex interplay between genetic and environmental factors. Studies in populations of European ancestry have demonstrated a higher concordance of refractive errors in monozygotic (MZ) twins compared to dizygotic (DZ) twins. However, there is a lack of studies on genetically informative samples of multi-ethnic ancestry. This study aimed to estimate the genetic contribution to astigmatism and myopia in the Mexican population. A sample of 1399 families, including 243 twin pairs and 1156 single twins, completed a medical questionnaire about their own and their co-twins diagnosis of astigmatism and myopia. Concordance rates for astigmatism and myopia were estimated in Mexican twins, and heritability and genetic correlations were determined using a bivariate ACE Cholesky decomposition method. The results showed a concordance rate of 0.74 for MZ twins and 0.50 for DZ twins for astigmatism, and a higher concordance rate in MZ twins, 0.74, compared to DZ twins, 0.54 for myopia. Heritability estimates were 0.66 for astigmatism and 0.62 for myopia, with a cross-trait genetic correlation of rA=0.82 and a phenotypic correlation of rP=0.80. These results are consistent with previous findings in other populations, providing evidence for a similar genetic architecture of these conditions in the multi-ethnic Mexican population.
