Refractive error is identified as the deviation from emmetropia that progresses either towards myopia or hyperopia. This phenotypic occurrence has been documented as being jointly due to genetics and the environment. This study looks to assess the contribution of heredity while considering the environment in refractive error development.
Using data from the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) study, there were 912 sibling pairs identified, ranging in age from 6 to 14 years, from various ethnic backgrounds. Linear regression analyses of the spherical equivalent and the ocular axial length were performed, controlling for age, while factoring in the environmental variables and ethnicity to determine their relevance. Heritability was calculated using the slope determined from the analyses of the spherical equivalent and axial length data of all available refractive errors.
The heritability (h2) found from the spherical equivalent data for this total sample produced a genetic variance of 0.784 with a 95% confidence interval of 0.648 - 0.920 (78.4% with a 95% CI 64.8% – 92.0%). The heritability (h2) found from the axial length data for this total sample produced a genetic variance of 0.834 with a 95% confidence interval of 0.708 - 0.958 (83.4% with a 95% CI 70.8% – 95.8%).
The best overall model determined from the greatest adjusted R square value for spherical equivalent was 0.146, and the best overall model for axial length resulted in an adjusted R square value of 0.175. Because of the shared genetics between siblings, a realistic R square value in this study’s would be 0.25, indicating that this model explains a reasonable portion of the variance of refractive error between siblings.
The heritability values and ranges found confirm that genetics are significant in the development of a subject’s spherical equivalent and axial length. Controlling for the environment had little impact on the heritability values that were determined.