Heritability of Central Corneal Thickness, Vertical Cup to Disc Ratio and Intraocular Pressure in an Isolated Greek Population

Abstract

Purpose: : To determine the heritability of central corneal thickness (CCT), vertical cup to disc ratio (CDR) and intraocular pressure (IOP) using an isolated Greek population.

Methods: : The clinical endophenotypes of interest (CCT, CDR and IOP) were measured in 597 people (338 females; 259 males); 376 of whom were linked in a single 11 generation pedigree. IOP was measured with two recently calibrated Tonopens. Optic nerve cupping was evaluated using direct ophthalmoscope in an undilated state. Pachymetry with an ultrasound Pachmate DGH55 instrument (DGH Technology, Exton, PA) was used to determine the CCT for each eye. Heritability was estimated using variance components modeling in SOLAR version 4.2. IOP was normalized using an inverse normal transformation to eliminate distribution errors.

Results: : CCT, CDR and IOP all showed significant heritability. Minimum CCT had a heritability of 0.655 (p=1.1x10^-15) with age, sex and diastolic blood pressure as significant covariates. The heritability of maximum IOP was 0.234 (p=1.0x10^-3) with systolic blood pressure as a significant covariate. Vertical disc to cup ratio had a heritability of 0.486 (p=2.1x10^-9) with age as a significant covariate.

Conclusions: : Within this Greek population CCT, CDR and IOP are all significantly heritable, making them excellent endophenotypes for further investigation.

Clinical Trial: : www.clinicaltrials.gov NCT000788762

Keywords: genetics • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology • optic disc