Glaucoma is a group of diseases that can lead to damage to the eye’s optic nerve and result in blindness. Open-angle glaucoma, the most common form of glaucoma, is one of the leading causes of blindness in the United States and the number one cause of blindness among African Americans. Glaucoma usually has no early symptoms, and by the time people experience problems with their vision, they usually have lost a significant amount of their sight.
The Early Manifest Glaucoma Trial
Prior to this study, the natural history of glaucoma was not well defined. Researchers did not know how rapidly, if at all, early stage glaucoma would progress if it were not treated initially. Because most eye care professionals immediately treat newly-diagnosed glaucoma by reducing intraocular pressure, the natural progression of the disease (in its untreated state) was not clear. Researchers were also unclear as to how effective treatment was for early stage glaucoma, because they did not know how rapidly the disease would progress without treatment.
This raised a key question: What price, in terms of side effects, inconvenience, and cost, can be considered acceptable when treatment effects are uncertain? To begin answering this question, a randomized study was designed with a control arm in which participants were followed without treatment as long as progression did not occur, thus not exposing study participants to unacceptable risks.
The Early Manifest Glaucoma Trial is the first large, controlled, randomized clinical trial to evaluate the effects of treatment versus no treatment on early stage glaucoma. More specifically, the study compared glaucoma progression in treated (lowering intraocular pressure) versus control patients. The study also determined how much treatment reduced eye pressure, and helped researchers chart the natural history of the disease.
Patient screening began in October 1992 and ended in April 1997. Study participants came from the Swedish cities of Malmö and Helsingborg. The study followed 255 patients, of which 66 percent were women. All patients were between 50-80 years of age, inclusive (average age: 68), and all had early stage glaucoma (open angle glaucoma or normal tension glaucoma) in at least one eye. One group (129 patients) was treated immediately with medicines and laser to lower eye pressure. A second, control group had 126 patients who were left untreated. Both groups were followed carefully and monitored every three months for early signs of advancing disease, using indicators that are extremely sensitive for detecting glaucoma progression. Any patient in the control group whose glaucoma progressed was immediately offered treatment.
After six years of followup, scientists found that in the control group, it took an average of 48 months to detect early signs of advancing disease. However, in the treated group, it took an average of 66 months – 18 months longer – to detect these early changes. In the treated group, eye pressure was lowered by an average of 25 percent. All the study participants will continue to be followed and regularly monitored.
The information from this clinical trial adds to the scientific knowledge gained from several other glaucoma-related studies supported by the National Eye Institute, including the Ocular Hypertension Treatment Study, the Advanced Glaucoma Intervention Study, and the Collaborative Initial Glaucoma Treatment Study.
The study is an example of international collaboration between Swedish and U.S. researchers. The National Eye Institute’s co-sponsorship, along with the Swedish Research Council, of this clinical trial allowed for a sufficiently large study to evaluate the research question of whether lower pressure inside the eye can slow glaucoma damage and subsequent vision loss.
The Early Manifest Glaucoma Trial is a collaborative effort that involves a clinical center at the Department of Ophthalmology of Malmö University Hospital at the University of Lund, Sweden, and its Satellite Center in Helsingborg, Sweden; an independent Data Center at the Department of Preventive Medicine, Stony Brook University, Stony Brook, New York; and a Disc Photography Reading Center at the Department of Ophthalmology in Lund at the University of Lund.