Researchers have discovered genetic markers for nearsightedness or myopia. Markers for other refractive errors like farsightedness have also been detected.
Gu Zhu, M.D., and colleagues have provided evidence that both nearsightedness and farsightedness are primarily inherited. In fact, they have also identified that the probable location of genes that help determine axial length, a key factor in these refractive errors is one the long arm of chromosome 5.
Axial length is a specific measurement from the front to back of the eye. If the person is nearsighted, this distance is longer than normal and in case of farsighted person, it is shorter.
This study mainly focussed on nearsightedness, or myopia, building on previous research on genetic aspects and environmental factors. Myopia compromises the eye's ability to focus on and see objects clearly at a distance. Especially when myopia is severe, it is expensive to treat and costly to patients' quality of life.
For the study, the researchers recruited 893 individuals from the Tasmania Twin Eye Study and Brisbane Adolescent Twin Study (BATS), Australia, and obtained axial length measurements. Then they examined the proportional impacts of genetic and environmental factors on axial length in this sample of identical and fraternal twins.
They found that genetic factors controlled almost 80 percent of the axial length values, after adjusting for age and sex. This is a groundbreaking study in the sense that it links axial length to the heritability of refractive error.
According to research team member, David Mackey, M.D., new measurement techniques may most probably make collection of axial length data routine in future research on myopia and other refractive error.
They later performed a genome scan on a subset of 318 individuals, and found "strong evidence" for the role of chromosome 5 (specifically the 5q region) in the inheritance of axial length.
And now, Dr. Zhu's team has initiated a genomic analysis of a larger study group to confirm and refine this finding.
Other studies have suggested that environmental factors such as regular periods of outdoor play during childhood, instead of having children concentrate only on reading and other "near work," might help reduce the development of nearsightedness, at least in those who are genetically susceptible. Identifying strong genetic markers could further this and other preventive efforts.
The study is published in the latest issue of Ophthalmology, the journal of the American Academy of Ophthalmology.