Objective: To examine aggregation of refraction, myopia, hyperopia, and astigmatism, as well as the 5-year change in each of these measures, among adult family members.
Design: Geographically defined, population-based cohort study in Beaver Dam, Wis. Participants were all 43 to 84 years of age in 1988. Family relationships among participants of the study were identified through interviews. The main outcome measures were noncycloplegic refractions. Aggregation was assessed by Pearson correlations and odds ratios (ORs) that both members of a pair were affected.
Results: Age-adjusted sibling correlation of refraction was 0.37 and the OR for a sibling to be myopic was 4.18, whereas the OR for being hyperopic was 2.87 (all statistically significant, P<.05). Correlations and ORs for parent-child and cousin relationships were smaller, and those for spousal relationships were not significant. Correlations and ORs for cylinder power and astigmatism were not statistically significant for most relationships considered. There were no statistically significant correlations or ORs for changes in any measure of refractive error.
Conclusions: The strong aggregation of refractive error, including myopia and hyperopia, among siblings along with weaker associations among parent-child and cousin pairs and no associations among spouses suggest a potential genetic influence on refractive error. There is no such suggestion for a genetic influence on the changes in refraction or in cylinder power and astigmatism.