Abstract
Purpose: :
To investigate the correlation in refractions between siblings and between children and their parents.
Methods: :
Refraction data were available starting in infancy for 116 children with at least one sibling. In families with more than two children, only data from the two oldest were included. All children were refracted in the laboratory by non-cycloplegic near retinoscopy until the age of 3 years and by non-cycloplegic distance retinoscopy thereafter. Parents were either refracted in the laboratory or their prescriptions were obtained from their eye care providers, with myopes defined as having a spherical equivalent refraction < -0.50 D. In a few cases parents were classified as myopic based on answers to a question asking if they wore glasses to see clearly at distance, and these data were included in analyses based on number of myopic parents. The correlations of spherical equivalent refractions (SER) of the right eye between siblings and between children and parents were evaluated by the Spearman rank correlation.
Results: :
Correlations of SER between siblings were significantly greater than zero at one year (r = 0.20, p = 0.03), 10 years (r = 0.22, p = 0.02) and 14 years (r = 0.48, p < 0.01), but not at 5 years (r = 0.16, ns). Mean SER at these ages ranged from 0.82 D at 1 year to -0.17 D at 14 years. Correlations of SER between siblings did not vary by number of myopic parents (0/1 vs. 2) for any age group. The correlations between the mean SER in siblings and parents were 0.21 (ns) at 1 year, 0.23 (p =0.04) at 5 years, 0.23 (p < 0.05) at 10 years, and 0.31 (p = 0.01) at 14 years.
Conclusions: :
The correlation between SER in siblings dropped slightly between 1 and 5 years and then increased up to 14 years, an age when myopia is more prevalent. At 14 years the correlation between siblings was higher than between offspring and parents, as reported previously. Our new finding is that in the early years the sibling-sibling and parent-offspring correlations are of a similar magnitude and lower than at 14 years.
Keywords: refraction • myopia • refractive error development