Mysteries of Glaucoma Revealed in Landmark CNIB-Funded Study
Open-angle glaucoma affects 67 million people worldwide, and about 250,000 people in Canada. A CNIB-funded study has made a major contribution to increasing our knowledge of this devastating disease.
The Canadian Glaucoma Study, recently released at the Canadian Ophthalmological Society conference in Montreal, provides, for the first time, conclusive evidence about four risk factors for the condition. Among them: women are twice as likely as men to develop glaucoma faster, and the chances of it worsening (for both men and women) rise 4 per cent for every year a person ages.
Open-angle glaucoma is the most common form of glaucoma, and involves damage to the eye’s optic nerve. It is often characterized by high intraocular pressure (IOP). The disease often progresses over years, and many people do not realize they have it until vision loss is permanent and untreatable.
The study also found that
- Patients who have an anticardiolipin antibody, associated with clotting in the circulatory system, or autoimmune disease, were four times more likely to progress. More research will be needed to fully understand the implications of this finding.
- The role of intraocular pressure (IOP) is even more significant than previously imagined. The study found that even small increases have an astonishing effect. Specifically, for every millimetre of mercury of increased IOP, the risk of progression increases by 20%.
- Interestingly, several risk factors previously thought to be important are actually not an issue. People with diabetes, hypertension and a history of cardiovascular disease were not more likely to progress than others.
The fact that even small increases in pressure can greatly increase the risk of progression underlies the importance of regular eye exams, particularly in older people, and is a wake up call for people who have the disease.
Because people who have glaucoma usually don’t have any symptoms, they can often lose significant vision before they are diagnosed and begin treatment. Regular eye exams can make sure that treatment is begun as early as possible. Open-angle glaucoma can be treated effectively with eye drops (and in some cases, surgery), but many patients do not follow their prescribed treatment regimen carefully enough, putting them at risk of losing vision. The study shows that it is essential for glaucoma patients to be rigourous about the use of their eye drops since not using drops for just a couple of days could cause an increase in eye pressure that can lead to vision loss. The study is also expected to guide the course of future research into the disease worldwide.
The Canadian Glaucoma Study is the largest and most rigorous clinical examination at glaucoma ever undertaken in Canada. It was designed with the unprecedented participation of leading glaucoma specialists across Canada and followed 258 patients in five university hospitals over a significantly long period, between 1994 and 2005.
“It is important to look at any slowly progressing disease over the long term,” said Dr. Balwantray Chauhan, the study’s principal investigator, and chair of vision research at Dalhousie University’s Faculty of Medicine. “But longitudinal trials of this duration are rarely funded. We’re grateful to CNIB and all our partners who made this possible.” CNIB contributed $1.8 million of the total $2.2 million cost of the study.
“As someone who was born with a severe form of open-angle glaucoma, I know how devastating this disease can be,” said CNIB president and CEO Jim Sanders after the study’s release. “CNIB is enormously proud to have supported Dr. Chauhan and the entire team who contributed to this groundbreaking research.”