Publications of A Racz

The inheritance of corneal endothelial cell density

Background: Although it is known that some corneal diseases and degenerations have a significant heritable background, heritability on corneal endothelial cell density (ECD) has never been clearly determined. Our aim was to determine the heritability of corneal ECD. Material and methods: Corneal ECD of 114 eyes (66 eyes of 33 monozygotic and 48 eyes of 24 dizygotic pairs; mean age 49.0 ± 15.5 years) was investigated by Konan Noncon Robo NSP-9900 specular microscopy. Structural equation modeling (ACE model) was applied. Results: Endothelial corneal cell density was highly heritable (82.0%, 95%CI, 70.0–92.0%), whereas the unique environmental contribution was 18.0% (95%CI, 8.0–29.0%). Shared environmental factors had no influence on the endothelial corneal cell density. Discussion: In this twin study, we established first that the density of the corneal endothelial cells is strongly heritable, which should stimulate future genetic studies to identify genes and pathways that are involved in determining ECD which might in turn lead to future treatments to prevent EC loss.

Genetic covariance between central corneal thickness and anterior chamber volume: a Hungarian twin study

Background: Few, and inconsistent, studies have showed high heritability of some parameters of the anterior segment of the eye; however, no heritability of anterior chamber volume (ACV) has been reported, and no study has been performed to investigate the correlation between the ACV and central corneal thickness (CCT). Methods: Anterior segment measurements (Pentacam, Oculus) were obtained from 220 eyes of 110 adult Hungarian twins (41 monozygotic and 14 same-sex dizygotic pairs; 80% women; age 48.6 ± 15.5 years) obtained from the Hungarian Twin Registry. Results: Age- and sex-adjusted heritability of ACV was 85% (bootstrapped 95% confidence interval; CI: 69% to 93%), and 88% for CCT (CI: 79% to 95%). Common environmental effects had no influence, and unshared environmental factors were responsible for 12% and 15% of the variance, respectively. The correlation between ACV and CCT was negative and significant (rph = −0.35, p < .05), and genetic factors accounted for the covariance significantly (0.934; CI: 0.418, 1.061) based on the bivariate Cholesky decomposition model. Conclusion: These findings support the high heritability of ACV and central corneal thickness, and a strong genetic covariance between them, which underscores the importance of identification of the specific genetic factors and the family risk-based screening of disorders related to these variables, such as open-angle and also angle closure glaucoma and corneal endothelial alterations.

Genetic effects on refraction and correlation with hemodynamic variables: a twin study

Spherical equivalent (SE) has not been linked to increased cardiovascular morbidity. Methods: 132 Hungarian twins (age 43.3±16.9 years) underwent refraction measurements (Huvitz MRK-3100 Premium AutoRefractokeratometer) and oscillometry (TensioMed Arteriograph). Results: Heritability analysis indicated major role for genetic components in the presence of right and left SE (82.7%, 95%CI, 62.9 to 93.7%, and 89.3%, 95%CI, 72.8 to 96.6%), while unshared environmental effects accounted for 17% (95%CI, 6.3% to 37%), and 11% (95%CI, 3.4% to 26.7%) of variations adjusted for age and sex. Bilateral SE showed weak age-dependent correlations with augmentation index (AIx), aortic pulse wave velocity (r ranging between 0.218 and 0.389, all p < 0.01), aortic systolic blood pressure and pulse pressure (r between 0.188 and 0.289, p < 0.05). Conclusions: These findings support heritability of spherical equivalent, which does not coexist with altered hemodynamics (e.g. accelerated arterial aging). Accordingly, SE and the investigated hemodynamic parameters seem neither phenotypically nor genetically associated. Keywords: arterial stiffness, augmentation index, genetics, heritability, refraction

Heritability of central blood pressure and arterial stiffness: a twin study

OBJECTIVE: Central blood pressure and aortic stiffness have been consistently reported as strong cardiovascular risk factors. Twin studies by comparing identical with nonidentical twins produce information on the relative contribution of genes and environment. METHODS: One hundred and fifty-four monozygotic (MZ) and 42 dizygotic (DZ) twin pairs (age 43 ± 17 years) from Hungary and the United States underwent brachial and central augmentation index (AIx), brachial and central pressure, and aortic pulse wave velocity (PWV) measurements with the invasively validated Arteriograph device. Bivariate Cholesky decomposition models were applied. RESULTS: Age-adjusted, sex-adjusted and country-adjusted heritability was 60.0% for central SBP [95% confidence interval (CI), 44.8-69.6%], 50.1% for aortic PWV (95%CI, 26.0-66.8%), 48.7% for aortic AIx (95%CI, 1.7-74.0%), 46.8% for brachial AIx (95%CI, 1.1-73.8%), 46.7% for central pulse pressure (PP) (95%CI, 12.4-61.4%), and 30.0% for brachial PP (95%CI, 0.0-53.4%). Central SBP and PP had strong bivariate correlations with brachial (r = 0.461 and 0.425) and central AIx (r = 0.457 and 0.419), as well as with aortic PWV (r = 0.341 and 0.292, all P < 0.001). Brachial PP had a weak correlation with brachial AIx (r = -0.118, P < 0.05), central AIx (r = -0.122, P < 0.05), and none with aortic PWV (r = 0.08, P = n.s.). Genetic factors explained a moderate phenotypic correlation between central PP, SBP, brachial SBP and aortic PWV. CONCLUSIONS: Central systolic and PPs, brachial PP, AIx, aortic PWV are moderately heritable. A moderate genetic covariance among aortic PWV and central PP, central SBP and brachial SBP was found.