Scientists at deCODE genetics and academic colleagues from Iceland, China, Sweden, the UK and Australia today report the discovery of the most important single-letter variation (SNP) in the sequence of the human genome yet associated with risk of primary open-angle glaucoma. This is the most common form of glaucoma and a major cause of blindness worldwide.

The SNP on chromosome 7 is common among Europeans, with approximately 6% of people of European ancestry carrying two copies of the at-risk version, putting them at roughly 60% greater risk of developing the disease than those who carry none. But among Chinese, the impact of the SNP is markedly different. In study groups from Hong Kong and Shantou, the at-risk version of the SNP is shown to be carried by less than 1% the population, but each copy carried confers more than five-fold increase in risk. The SNP is near the genes encoding caveolin 1 and 2, membrane proteins that are expressed in the meshwork that drains fluid from the eye, a process that if disturbed can increase pressure on the optic nerve and lead to glaucoma.

The key to reducing the personal and public health impact of glaucoma is early diagnosis and treatment to slow the loss of sight. Discoveries such as today’s, which follows on our previous landmark findings in exfoliation glaucoma, are important because we can fold them directly into tests to target screening and to detect and treat more disease earlier. Moreover, among Chinese this latest SNP alone can define a small fraction of the population that should be very carefully screened. This underscores the value of being able to systematically analyze the impact of genetic risk factors across continental ancestries. Not only are these markers medically useful, they also tell us a bit about evolution and the spread of humanity across the globe,” said Kari Stefansson, deCODE’s Executive Chairman and President of Research and senior author of the study.

The authors would like to thank the more than 40,000 people who participated in this study, both glaucoma patients and control subjects. The paper, “Common variants near CAV1 and CAV2 are associated with primary open-angle glaucoma,” is published online in Nature Genetics and will appear in an upcoming print edition of the journal.

Primary open-angle glaucoma is a disease in which the optic nerve becomes damaged, leading to a progressive loss of sight. It affects tens of millions of people worldwide, mostly those over the age of 50. Incidence increases with age and varies between populations. Other known risk factors include high blood pressure and diabetes. Current treatments include eye drops that reduce pressure on the optic nerve, as well as surgery.