Genes may be main culprit in myopia 25/2/03. By Penny Bailey A new study indicates that heredity is a primary cause of short-sightedness. The study also suggests that the amount of time a child spends studying or reading can influence the development of myopia, or short-sightedness, to a small extent.

Donald Mutti, Professor of Optometry at Ohio State University, and fellow researchers found that most of the risk for developing myopia is based on whether a child has none, one or two myopic parents.

The study – published in the December 2002 issue of Investigative Ophthalmology & Visual Science – looked at 366 eighth-grade children. The researchers gathered information on the children's current prescriptions for vision correction and those of each parent. They also collected scores from a basic reading and language skills test, and asked parents to record how much time their child spent doing a variety of activities in a week, such as studying, reading for pleasure, playing sports, watching TV and using a computer.

About one out of five children in the study had myopia, while nearly three-quarters of the children had normal vision. Fewer than 10 per cent were long-sighted. A third of the children with two myopic parents had myopia and nearly one out of five children with one myopic parent had myopia. Fewer than ten children without myopic parents had myopia.

These findings indicate that myopia seems to follow a dose-dependent pattern: the chance a child will develop myopia greatly increases based on the number of myopic parents he or she has. However, having two myopic parents does not mean for certain that a child will develop myopia. Although the chance is much greater, this is not a straightforward inheritance pattern.

The findings also found a definite link between paper-based pursuits, such as studying and reading, and myopia. The myopic children spent about two hours more per week studying and reading for pleasure than did the children with normal vision, and scored about 10 per cent higher than non-myopic children on basic reading and language skills. They also spent about two fewer hours per week in sports activities than non-myopic children.

However, there was no such link between myopia and watching TV or using a computer. Short-sighted children spent about the same amount of time watching television and playing video games in a week as did children with normal vision.

The next step is to look at how these factors – both hereditary and environmental – might help vision care providers predict which patients will develop myopia. Because myopia seems to be inherited, Donald Mutti and his colleagues are looking for genetic markers to develop a predictive test for children and adults.

Image credit: Anthea Sieveking

Further reading

Mutti DO et al. Parental myopia, near work, school achievement, and children's refractive error. Invest Ophthalmol Vis Sci 2002 Dec;43(12):3633-40. Abstract ; Full text