Genetic, environmental twin studies provide clues to myopia
With myopia on the rise, greater understanding of genetic and environmental factors is needed to refine interventions that may curtail disease progression.
Take-home message: With myopia on the rise, greater understanding of genetic and environmental factors is needed to refine interventions that may curtail disease progression.
Reviewed by David A. Mackey, MD
Perth, Australia-Genetic research is likely to play an important role in the course of myopia research. Twin studies have been invaluable in taking researchers to the point they have reached today, said David A. Mackey, MD.
Interestingly, ophthalmology traits were found to have the highest heritability of any group of traits measured in a meta-analysis of the heritability of human traits based on twin studies conducted over 50 years.
“This is probably related to our ability to accurately phenotype and define disease and our high precision at measuring ocular structures,” said Dr. Mackey, managing director and chairman, Centre for Ophthalmology and Visual Science, University of Western Australia, Perth.
In a twin study of the central corneal thickness, Dr. Mackey demonstrated the tight correlation of corneal thicknesses when one identical twin was compared with his or her sibling.
In contrast, in non-identical twins, there also was a correlation between the central corneal thicknesses but it was nowhere near as tight as that seen in the identical twins.
“This difference between the two types of twins indicates that there is a strong genetic component,” he said.
Myopia and refractive error were shown to have very high heritability scores in the twin studies. However, axial length and corneal curvature had even higher scores, suggesting that they are more genetically driven, according to Dr. Mackey.
A strong message in twin studies was that genes and environment did not act independently of each other and that the combination of the two factors was a driving force.
“It is by working out how the two work together that we should be able to understand the etiology of myopia,” he said.
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