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Christopher J. Hammond, Harold Snieder, Clare E. Gilbert, Tim D. Spector; Genes and Environment in Refractive Error: The Twin Eye Study. Invest. Ophthalmol. Vis. Sci. 2001;42(6):1232-1236.
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purpose. A classical twin study was performed to examine the relative importance
of genes and environment in refractive error.
methods. Refractive error was examined in 226 monozygotic (MZ) and 280 dizygotic
(DZ) twin pairs aged 49 to 79 years (mean age, 62.4 years). Using a
Humphrey-670 automatic refractor, continuous measures of spherical
equivalent, total astigmatism, and corneal astigmatism were recorded.
Univariate and bivariate maximum likelihood model fitting was used to
estimate genetic and environmental variance components using
information from both eyes.
results. For the continuous spectrum of myopia/hyperopia, a model specifying
additive genetic and unique environmental factors showed the best fit
to the data, yielding a heritability of 84% to 86% (95% confidence
interval [CI], 81%–89%). If myopia and hyperopia (≤ −0.5
D and ≥ 0.5 D, respectively) were treated as binary traits, the
heritability was 90% (95% CI, 81%–95%) for myopia and 89% (95%
CI, 81%–94%) for hyperopia. For total and corneal astigmatism,
modeling showed dominant genetic effects are important; dominant
genetic effects accounted for 47% to 49% of the variance of total
astigmatism (95% CI, 37%–55%) and 42% to 61% of corneal
astigmatism variance (95% CI, 8%–71%), with additive genetic
factors accounting for 1% to 4% and 4% to 18%, respectively (95%
CIs, 0%–13% and 0%–60%, respectively).
conclusions. Genetic effects are of major importance in myopia/hyperopia;
astigmatism appears to be dominantly
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