Older dads lift odds of high myopia

Researchers find link to mutation in gene that causes nearsightedness

The older a father is, the higher the possibility his child will suffer from early-onset high myopia due to a mutation in a gene, Chinese scientists found.

It is the first causal gene that has been proven, through complete animal model tests, to lead to high myopia, nearsightedness of－6.00 diopters, said Jin Zibing, one of the leading researchers on a team from Wenzhou Medical University in Zhejiang province.

The gene is mainly expressed in the eye's ciliary body and neural retina, which may offer key insight into future medical treatment and prevention of high myopia, the cause of which remains unclear, Jin said.

"Through our research we speculated that the ciliary body and neural retina are probably the root place where high myopia happens, which may help future treatment to be more accurately directed," he said.

On Saturday, the China Medicinal Biotech Association and the journal Chinese Medicinal Biotechnology listed the team's research result as one of last year's top 10 progresses in the medical biotechnology field in China.

In May, a paper about their discovery was published in the Proceedings of the National Academy of Sciences of the United States.

Jin, also an ophthalmologist at the Eye Hospital at Wenzhou Medical University, said the research started with the collection of patient samples to find out possible reasons for early-onset high myopia among children under 6 years old.

"Preschool children encounter fewer risks from environmental pressures. We propose that the condition of early-onset high myopia is driven by genetic predisposition more than environmental factors," he said.

Jin said the team found 18 families where the parents did not have myopia but a child younger than 6 did. They conducted gene sequencing and found that a mutation had occurred in the child's BSG gene, but not in those of the parents.

"Interestingly we found in these cases the fathers' reproductive ages are relatively old. And for most of the 12 families who have two children, the elder child did not suffer myopia while the younger one had high myopia," Jin said.

In lab tests, mice showed lengthened eye axis when the mutated gene was knocked in, manifesting symptoms of nearsightedness, and it proved their assumption.

Myopia is the most common ocular disease and uncorrected myopia is the leading cause of vision impairment worldwide, according to the World Health Organization.

Jin said the team now plans to conduct the study with a larger sample size.

"We also want to figure out whether early-onset high myopia is related to in vitro fertilization, which is gaining in popularity when some couples of advanced reproductive age are eager to have a second child," Jin said.