Purchase this article with an account.
L.S. Kearns, J.R. MacKinnon, A.W. Hewitt, S. Shekar, S.A. Brown, J.L. Pouslen, C.J. Hammond, O. Bigault, N.G. Martin, D.A. Mackey; Genetic Influence on Intraocular Pressure: The Twins Eye Study in Tasmania . Invest. Ophthalmol. Vis. Sci. 2006;47(13):178.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Elevated intraocular pressure (IOP) is an important risk factor for open–angle glaucoma and reducing IOP is associated with a reduction in the rate of visual field progression. The aim of this study was to examine the heritability and associations of IOP in the general population.
A classical twin study design was adopted. Participants, who were recruited through the Twins Eye Study in Tasmania, underwent ocular phenotyping. IOP was measured either using a tonopen or Goldmann applanation tonometry. Covariance of IOP was compared between monozygotic (MZ) and dizygotic (DZ) twins. Best–fit structural equation modelling was performed using the Mx program.
In total 148 MZ twin pairs and 182 DZ twin pairs with a mean age of 22.1 ± 17.6 years, were examined. The mean ± SD IOP across all MZ twins was 15.5 ± 3.1 and did not significantly differ to that of DZ twins (15.8 ± 3.1; p=0.21). The maximum likelihood estimate of Pearson’s correlation coefficient for IOP was 0.57 (95%CI: 0.45–0.66) in the MZ twin pairs and 0.40 (95%CI: 0.27–0.51) in the DZ twin pairs. The best–fitting model adjusting for tonometry method, was one where additive genetic effects accounted for 34.1% (95%CI: 3.7–63.6%) of the variation, whilst common and unique environmental effects accounted for 22.7% (95%CI: 0.0–46.3%) and 43.2% (95%CI:34.0–54.9%) of the variance respectively. IOP was positively associated with central corneal thickness (CCT) (R2=0.0296, p=0.0005) and negatively associated with time of day (R2=0.0112, p=0.0116) and axial length (R2=0.0166, p=0.0098). There was a significant difference in CCT covariance between opposite sex twin pairs and same sex twin pairs.
The estimated heritability for IOP in this study is similar to previous family based studies. Dominant genetic effects may be a source of variation, however, this cohort comprised of twins reared together and it was not possible to estimate this concurrently with common environmental effects.
This PDF is available to Subscribers Only