Purpose:
To investigate to what extent genetic factors contribute to glaucoma, by estimating the heritability of optic disc characteristics within an isolated population in the Netherlands.
Methods:
We assessed ophthalmologic and non–ophthalmologic clinical parameters among 607 subjects from the Erasmus Rucphen Family (ERF) study, an extended pedigree study in a Dutch genetic isolate. Optic disc area, rim area, rim/disc area ratio and cup shape measurement were determined by confocal scanning laser ophthalmoscopy (HRT II; Heidelberg Engineering GmbH, Dossenheim, Germany). Risk associations were assessed by univariate and multivariate regression analyses, and a final model for heritability estimation was determined. A variance component maximum likelihood approach (SOLAR 2.1.2. software package) was used to divide the total phenotypic variance of the optic disc parameters into additive genetic and environmental elements. We estimated heritability as the proportion of phenotypic variance explained by additive genetic effects after adjustment for covariates.
Results:
The mean age was 49.3 years (range 18.2–81.2). 86.4% of the subjects were inbred, i.e. had consanguineous parents. Inbreeding only significantly effected rim area (ß = 0.119, p–value = 0.004). Age, sex, length of eye axis, spherical equivalent, and systolic and diastolic blood pressure were significantly associated with at least one of the optic disc parameters. Heritability estimates for the studied parameters, adjusted for the appropriate covariates, have been reported in the table. These results were independent of intraocular pressure.
Conclusions:
Variance in optic disc morphology is strongly explained by additive genetic effects. These results encourage the search for genes in the pathogenesis of glaucoma in this population.
Keywords: genetics • optic disc • clinical (human) or epidemiologic studies: risk factor assessment