Sibling and Parental Analysis of High and Moderate Myopia in the Genes in Myopia (GEM) Study

Abstract

Abstract: : Purpose: To examine the heritability of high and moderate myopia in siblings and parent–sibling families, collected through the Genes in Myopia (GEM) study in Australia. Methods: 1780 patients with myopia of at least –3D in each eye who attended a Melbourne laser clinic were contacted by mail. 244 probands (mean age of 47 years) with a family history of myopia have so far taken part in this study. An additional 290 individuals recruited from the proband’s families have also been examined. All individuals underwent a detailed eye examination including biometric measurements, risk factor questionnaire and had a blood sample taken. Results: 244 families were available for this study where there was information on 2 or more siblings. Myopic probands (–6D or worse) were found to have a myopic sibling of –6D or worse in 13% of cases, a myopic sibling of –3D to –6D in 56.5% of cases and a myopic sibling of –1D to –3D in 82.5% of cases. In the case of myopic probands (–3D to –6D), they had a myopic sibling of –3D or worse in 35.3% of cases and a myopic sibling of –1D or worse in 54.9% of cases. In 50 families, information was available on myopic status for both parents and siblings. 18 probands worse than –6D had at least one myopic parent (–1D or worse) in 66% of cases. In 32 families where the proband was between –1D to –6D, at least one myopic parent was present in 78% of cases. In 17% of probands (–6D or worse), both parents presented with myopia. However in 16.5% of probands (–6D or worse), neither parent presented with myopia. The sibling risk (_s) for high myopia is 10 and for moderate myopia is 7.6. Conclusions: The risk of a high myope (–6D or worse) having a highly myopic sibling is small. However the risk of a myopic proband having a sibling with myopia is high. Continued sibling examination will lead to a more precise value for _s in both high and moderate myopia families in this study. In sibling–parent families so far examined, probands with myopia worse than –1D present with at least one myopic parent in a majority of cases.

Keywords: myopia • genetics