Browsing by Subject "Twins"

Now showing 1 - 4 of 4
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    Disparity between central and peripheral refraction inheritance in twins
    (Nature Research, 2021-06-09) Pusti, D.; Benito, A.; Artal, P.; Madrid Valero, Juan José; Ordoñana Martín, Juan Ramón; Física
    The last decades have witnessed a sudden increase in myopia incidence among youngsters that have been related to modern lifestyle along with the use of emerging technologies affecting visual exposure. Increasing exposures to known risk factors for myopia, such as time spent indoors, close-distance work, or low-light conditions are thought to be responsible for this public health issue. In most cases, development of myopia is secondary to a vitreous chamber enlargement, although the related mechanisms and the potential interaction between central and peripheral retinal area remain unclear. For a better understanding, we performed a classical twin study where objective refractive error along 70° of horizontal retinal arc was measured in 100 twin pairs of university students, 78% of which showed manifest myopia. We found the variance of shared environmental origin (range 0.34 to 0.67) explained most of the objective refractive error variance within central 42° of the retina (22° temporal to 19° nasal), whereas additive genetic variance (range 0.34 to 0.76) was predominant in the peripheral retinal areas measured. In this sample of millennial university students, with a large prevalence of myopia, environmental exposures were mostly responsible for inter-individual variation in the retinal horizontal area surrounding the macula, while their relative weight on phenotypic variance was gradually descending, and replaced by the variance of genetic origin, towards the retinal periphery.
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    Impact of Genetic and Environmental Factors on Peripheral Refraction
    (Association for Research in Vision and Ophthalmology, 2024-10-23) Pusti, D.; Benito, A.; Artal, P.; Madrid Valero, Juan José; Ordoñana Martín, Juan Ramón; Física
    Investigate genetic and environmental influences on refractive errors in monozygotic (MZ) and dizygotic (DZ) twin pairs. We assessed foveal and peripheral refractions in 54 MZ and 46 DZ twins, capturing three scans across the retina. The study focused on spherical equivalent (M) at the fovea (MLOS) and changes in midperipheral (δMmid-periphery), and peripheral (δMperiphery) defocus, along with nasal-temporal asymmetry (root mean squared error [RMSEASY]) and image shell contour (RMSEAVG). Genetic and environmental contributions were analyzed using structural equation models. No significant differences were observed between MZ and DZ twins for the examined variables. Intraclass correlations (ICC) indicated an important difference in genetic influence between MLOS, with the MZ twin pairs showing a higher correlation (0.83) than DZ (0.69) pairs, and δMperiphery, because the ICC for the MZ doubled (0.87) that of the DZ (0.42) pairs. Heritability estimates from the ACE model confirmed the large difference on genetic factors' influence on the variance for MLOS (0.13) and δMperiphery (0.77) change in refractive error. RMSEASY and RMSEAVG metrics showed significant genetic impact, particularly pronounced in the peripheral measurements, revealing high genetic control. The study delineates a marked environmental impact on central refractive errors, whereas genetic factors had a more significant influence on peripheral refractive variance and retinal image traits. Findings of the ACE model highlight the intricate genetic and environmental interplay in refractive error development, with a notable genetic dominance in peripheral vision characteristics. This suggests potential genetic targets for interventions in myopia management and emphasizes the need for personalized approaches based on genetic predispositions. Understanding the impact of genetics and environment on peripheral refraction is essential for deepening our fundamental knowledge of myopia and guiding the development of advanced myopia control strategies.
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    Inheritance of Refractive Error in Millennials
    (Nature Research, 2020-05-18) Pusti, D.; Benito, A.; Artal, P.; Madrid Valero, Juan José; Ordoñana Martín, Juan Ramón; Física
    Over the last decades, the prevalence of myopia has suddenly increased, and at this rate, half of the world's population will be myopic by the year 2050. Contemporary behavioural and lifestyle circumstances, along with emergent technology, are thought to be responsible for this increase. Twin studies mostly reported a high heritability of refractive error across ethnicities. However, heritability is a population statistic and could vary as a result of changing environmental conditions. We studied the variance of refractive error in millennials with 100 twin pairs of university students in southeast Spain. The study population presented a high prevalence of myopia (77%). Statistical analysis showed the variance of refractive error in this group of young twins was mainly driven by the shared environment and, to a lesser extent, by additive genetic factors. We found an increase in myopia prevalence accompanied by a decrease in heritability in this sample of millennials in contrast with results from a previous generation group from the same ethnic origin.
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    Otra vez sobre Rómulo y Remo: Ciro y la leyenda del fundador
    (2017-03-09) Cascón Dorado, Antonio
    La leyenda de Rómulo es un material literario, que debe ser analizado, principalmente, desde una perspectiva filológica, teniendo en cuenta los fenómenos propios en la trasmisión literaria de este tipo de narraciones, semejantes a otras como el mito, la fábula o el exemplum. Se trata de una versión más de la "leyenda del fundador", con elementos habituales en otros relatos de fundación de ciudades, naciones o religiones. Su proximidad a la leyenda de Ciro, sobre todo en su parte final, permite pensar en un autor griego que en su composición tuvo en cuenta el relato legendario del nacimiento del rey persa, pero es necesario explicar el origen de las diferencias entre ambas leyendas, sobre todo en su parte inicial.