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Christopher J. Hammond, Donald D. Duncan, Harold Snieder, Marlies de Lange, Sheila K. West, Tim D. Spector, Clare E. Gilbert; The Heritability of Age-Related Cortical Cataract: The Twin Eye Study. Invest. Ophthalmol. Vis. Sci. 2001;42(3):601-605.
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© ARVO (1962-2015); The Authors (2016-present)
purpose. A classical twin study was performed to establish the relative
importance of genes and environment in cortical cataract.
methods. Five hundred six pairs of unselected female twin volunteers (226
monozygotic and 280 dizygotic) with a mean age of 62 years (range,
49–79 years) were examined. Cortical cataract was assessed using the
slit-lamp–based Oxford Clinical Cataract Classification and Grading
System (clinical grading) and the Wilmer Automated Grading System,
which analyzed digital retroillumination images of subjects’ lenses
(digital grading). The worse eye categorized score for each individual
was used in maximum likelihood path modeling of the correlations within
twin pairs. These correlations were used to determine the underlying
liability to cortical cataract.
results. Prevalence of significant cortical cataract (≥5% of lens area) was
similar in monozygotic and dizygotic twins, occurring in 19.4% and
20.6% with the clinical grading system and 24% and 23% using the
digital grading system, respectively. Modeling suggested liability to
cortical cataract is explained by additive and dominant genes,
individual environment, and age. Estimates of the broad sense
heritability of cortical cataract were 58% (95% confidence interval[
CI], 51%–64%) for the clinical grading system and 53% (95% CI,
45%–60%) for the digital system. Dominant genes were estimated to
contribute to 38% (95% CI, 1%–64%) of the genetic effect with the
clinical grading and 53% (95% CI, 28%–60%) with the digital
grading. Individual environment explained 26% and 37% and age 16%
and 11% of cortical cataract variance in clinical and digital
conclusions. Genetic effects are important in the development of cortical cataract
and involve the action of dominant genes.
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