Heritability of refractive error and ocular biometrics - the Genes in Myopia (GEM) twin study
Dirani M, Chamberlain M, Shekar SN, Islam AF, Garoufalis P, Chen CY, Guymer RH, Baird PN · 2006
grade Btwin-adoptionindependentreplicated
Sample
1,224 twins (345 MZ and 267 DZ pairs), aged 18-88
Population
Australian adult twin registry
Design
Classical twin study with objective refraction and partial coherence interferometry biometry. Best-fitting model was a sex-limited ADE model (additive genetic, dominance, unique environment) - shared environment was not required, consistent with the TwinsUK finding. Adult sample.
Key findings
Heritability of spherical equivalent was 88% in men and 75% in women; heritability of axial length was 94% and 92% respectively. Additive genetic effects dominated refractive-error variance while axial-length variance was explained largely by dominance effects. Intrapair correlations were significantly higher in MZ than DZ pairs for all measures.
Genetic confound
This is a heritability estimate, so the equal-environments assumption of the twin design is the relevant caveat; the estimate is from an adult sample spanning 70 birth years, which can inflate heritability relative to a same-cohort childhood estimate.
DOI / URL
Effects
| Outcome | Metric | Value | Measure | Timing | Vs | Horizon | Class |
|---|---|---|---|---|---|---|---|
| Spherical equivalent refractive error | h2 (classical twin, sex-limited ADE) | 88% in men; 75% in women | standardized | adult cross-section, ages 18-88 | none | not-applicable | health |
| Axial length | h2 (classical twin, sex-limited ADE) | 94% in men; 92% in women | standardized | adult cross-section | none | not-applicable | health |
| Shared environmental variance (C) in refractive error | C variance | not required by the best-fitting model | standardized | adult cross-section | none | not-applicable | health |