In a world first, an Australian research team has discovered two new genes linked to open angle glaucoma.
A study, published in last months (May) prestigious international science journal, Nature Genetics, has established that 18 per cent of the population carry risk variants at these two genes, is the only study of severe glaucoma cases in the world.
Glaucoma is the leading cause of irreversible blindness worldwide, affecting an estimated 300,000 people in Australia, of which half are currently undiagnosed. The disease advances very slowly and many people are not diagnosed until they start bumping into things.
“Treatments that we have are (only) able to slow the disease down and potentially (stop it) getting worse, but none of the treatments at this stage can bring back vision that’s already lost,” says Craig.
People who had these gene variants were three times more likely to have glaucoma than the general population…
People with a family history have been known to have a greater risk of glaucoma, but until now, only one gene – ‘myocilin’ – has been linked to the disease. That gene is believed to account for just 3 per cent of cases.
Dr. Craig and his colleagues studied 1,500 glaucoma cases and 8,500 control cases in Australia and New Zealand.
They compared the DNA of the two groups and found two common gene variants that seemed to be associated with a greater risk of glaucoma.
People who had these gene variants were three times more likely to have glaucoma than the general population, says Dr. Craig. He says the association is even stronger for severe blinding glaucoma and estimates the genes variants could be responsible for a substantial proportion of glaucoma cases in the wider population – possibly 30 per cent.
The study is significant because although open angle glaucoma is the most common form of the disease, it is poorly understood and difficult to diagnose in its early stages. While usually associated with raised fluid pressure within the eye, 20 per cent of people with glaucoma don’t have this raised pressure.
“Many cases still remain undiagnosed until irreversible loss of vision has occurred,” Dr Craig said.
The research findings may help to prioritise treatment for suspected glaucoma patients, as well as help to offer more effective monitoring and more targeted intervention. This is an opportunity to develop a completely new treatment pathway using different drugs to modulate expression of genes.
Current treatments including eye drops, laser and surgery, are aimed at reducing pressure in the eye but according to Dr. Craig, sometimes they don’t work.
The researchers carried out tests in rats with glaucoma and found that one of the newly discovered gene variants was more active in the retina.
They believe it could be linked to death of the optic nerve, independent of pressure from fluid in the eye.
Dr. Craig says further research could show that a drug that blocks the expression of this gene could slow down the damage to the optic nerve in all cases of glaucoma.
The ground-breaking survey was led by Dr. Craig and his team from Flinders University who collaborated with groups from the University of South Australia, the University of Queensland, Queensland Institute of Medical Research and the University of Western Australia.
“This study is the culmination of five years’ work, which started with the foundation of the Registry. Before anyone else in the world, our South Australian team achieved these outstanding results,” Dr Craig said.
For more information on other Australian firsts, go to our main story: ‘Taking the Lead: Australia’s World First Optical Industry’ on page 20.