Researchers have found further proof that myopia and hyperopia are inherited, and they identified the probable location of genes that help determine axial length, a key factor in these refractive errors. These findings are reported in the June issue of Ophthalmology.

Focusing on myopia, Gu Zhu, M.D., Ph.D., and colleagues obtained axial length measurements and DNA samples from 893 individuals from the Tasmania Twin Eye Study and Brisbane Adolescent Twin Study in Australia. Using structural equation modeling on the entire sample, the researchers analyzed the proportional impacts of genetic and environmental factors on axial length.

Genetic factors explained approximately 80% percent of the axial length values, after adjusting for age and sex, they found.

Research team member David Mackey, M.D., says that new measurement techniques will likely make axial length data collection routine in future research on myopia and other refractive error.

The researchers also performed a genome scan on a subset of 318 individuals, and they found strong evidence for the role of chromosome 5 (specifically, the 5q region) in the inheritance of axial length. Dr. Zhus team has launched 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, rather than 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.

Also, the identification of strong genetic markers could further preventive efforts, researchers say.

Zhu G, Hewitt AW, Ruddle JB, et al. Genetic dissection of myopia: evidence for linkage of ocular axial length to chromosome 5q. Ophthalmology 2008 Jun;115(6):1053-7.

Vol. No: 145:07Issue: 7/15/2008