Abstract
PurposeThe purpose of this work was to investigate the heritability of potential glaucoma endophenotypes. We estimated for the first time the heritability of the pulsatility of choroidal blood flow. We also sought to confirm the heritability of corneal hysteresis, central corneal thickness, and 3 ways of measuring intraocular pressure.MethodsMeasurements were performed on 96 first-degree relatives recruited from Maisonneuve-Rosemont Hospital in Montreal. Corneal hysteresis was determined using the Reichert Ocular Response Analyser. Central corneal thickness was measured with an ultrasound pachymeter. Three measures of intraocular pressure were obtained: Goldmann-correlated and corneal compensated intraocular pressure using the Ocular Response Analyser, and Pascal intraocular pressure using the Pascal Dynamic Contour Tonometer. The pulsatility of choroidal blood velocity and flow were measured in the sub-foveolar choroid using single-point laser Doppler flowmetry (Oculix). We estimated heritability using maximum-likelihood variance components methods implemented in the SOLAR software.ResultsNo significant heritability was detected for the pulsatility of choroidal blood flow or velocity. The Goldman-correlated, corneal compensated, and Pascal measures of intraocular pressure measures were all significantly heritable at 0.94, 0.79, and 0.53 after age and sex adjustment (p = 0.0003, p = 0.0023, p = 0.0239). Central corneal thickness was significantly heritable at 0.68 (p = 0.0078). Corneal hysteresis was highly heritable but the estimate was at the upper boundary of 1.00 preventing us from giving a precise estimate.ConclusionCorneal hysteresis, central corneal thickness, and intraocular pressure are all heritable and may be suitable as glaucoma endophenotypes. The pulsatility of choroidal blood flow and blood velocity were not significantly heritable in this sample.
Highlights
Most cases of open-angle glaucoma are probably multifactorial, involving multiple contributing genetic and environmental factors
Intermediate phenotypes, called endophenotypes, are powerful tools in the search for genes contributing to multifactorial human diseases as they are likely to be more directly influenced by the genes than the resulting disease phenotype and they provide greater statistical power [1,2,3,4]
Phenotypes such as intraocular pressure and central corneal thickness may be suitable as endophenotypes in glaucoma since they are well-established risk factors for glaucoma [5,6]
Summary
Most cases of open-angle glaucoma (including normal tension glaucoma) are probably multifactorial, involving multiple contributing genetic and environmental factors. Intermediate phenotypes, called endophenotypes, are powerful tools in the search for genes contributing to multifactorial human diseases as they are likely to be more directly influenced by the genes than the resulting disease phenotype and they provide greater statistical power [1,2,3,4]. Phenotypes such as intraocular pressure and central corneal thickness may be suitable as endophenotypes in glaucoma since they are well-established risk factors for glaucoma [5,6]. Phenotypes that are heritable are useful endophenotypes in the search for genes contributing to a complex disease
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