A Genetic Marker for Nearsightedness?

Studying twins is a helpful way to learn about genetic vs. environmental factors in any given health condition, and in Australia, there are large twin studies being done in the states of Tasmania, Victoria, and Queensland. Their goal is to identify the genes underlying common eye diseases such as glaucoma and myopia.

One group, headed by Dr. David Mackey and Dr. Gu Zhu, is investigating the theory that both myopia and hyperopia are primarily inherited. This group worked with 893 individuals to measure the eye's axial length -- its dimension from front to back.

How Does Myopia Work?

A myopic eye cannot see clearly at far distances because it has too great an axial length. The cornea (clear front cover) curves outward too far from the retina in the back of the eye, so that incoming light focuses in front of the retina instead of accurately on it. LASIK corrects this problem by slightly flattening the cornea, which reduces the axial length.

The Research Findings

Their sample included both genetic and fraternal twins. On a subset of 318 individuals, researchers found "strong evidence" for chromosome 5 being responsible for axial length. They have since started a larger study to confirm this finding. They also identified the probable location of genes that help determine the eye's axial length (on the long arm of chromosome 5). After adjusting for age and gender, they found that genetic factors account for about 80 percent of axial length values.

It has been found in unrelated studies that when children enjoy regular periods of outdoor play, rather than being confined to reading or computer play, they can apparently avoid some of the nearsightedness they might otherwise be susceptible to genetically.

Preventing myopia is a goal of many researchers, and Dr. Mackey and Dr. Zhu used new measurement techniques which they think will probably make measurement of axial length a routine procedure in future research on myopia and hyperopia.

If you would like to know more about myopia, the first step would be to contact a fully-qualified ophthalmologist and arrange for a consultation.