Lessons Learned from the Early Manifest Glaucoma Trial
Dr. Nathan M. Radcliffe
In the field of glaucoma there have been several large, prospective randomized trials that have described outcomes for thousands of patients with glaucoma or ocular hypertension. We have learned a tremendous amount from these studies about glaucoma progression, its risk factors, and how many types of treatment influence patient outcomes.
The first step into this line of research was made when Swedish and U.S. researchers, supported by the National Eye Institute and the Swedish Research Council, screened roughly 33,000 individuals 55 to 79 years of age in Malmö, Sweden over a five year period. The identified open angle glaucoma in 1.23% of those screened and found that disease severity was evenly distributed between early, moderate and severe disease but that 2/3 of subjects had unilateral glaucoma.1
Because it had not been clearly proven in 1992, the Early Manifest Glaucoma Trial was created to settle the question of whether IOP lowering treatment delays or stops the progression of glaucoma. Patients were randomized to receive either betaxolol and argon laser trabeculoplasty or observation and were followed carefully for progression using a sensitive assessment of the visual field. Treatment was able to reduce the intraocular pressure by 25% and after an average of 8 years, 59% of those treated progressed compared to 76% of those who were not treated. The type of glaucoma had a large influence on the likelihood of progression. After 6 years, 68% of all patients had progressed, but the proportion of patients progressing was lower (56%) in normal tension glaucoma and higher (93%) with exfoliation glaucoma.2
In the study, betaxolol was initiated first and then ALT was performed. On average, ALT lowered IOP by 12.6 ± 20.5%, but for every 3mm Hg higher the baseline IOP, the laser reduced the IOP by an additional 2 mm Hg.3 Interestingly, the laser worked better in some surgeon’s hands than in others, with some surgeons achieving a 5.8 mm Hg IOP reduction on average while others performed lasers that resulted in pressure elevations of 1.3 mm Hg.
Finally, the EMGT was an early study to demonstrate risk factors that have gained new importance in recent years. Lower systolic ocular perfusion pressure and (for patients with a high IOP) a thinner cornea were both found to increase progression risk.4
In summary, for a study that began in 1992, the EMGT continues to provide tremendous insights into glaucoma management. We will serve our patients well by keeping the gems from this study at the top of our minds.
1. Heijl A, Bengtsson B, Oskarsdottir SE. Prevalence and severity of undetected manifest glaucoma: results from the early manifest glaucoma trial screening. Ophthalmology. 2013 Aug;120(8):1541-5.
2. Heijl A, Bengtsson B, Hyman L, Leske MC; Early Manifest Glaucoma Trial Group. Natural history of open-angle glaucoma. Ophthalmology.
3. Heijl A, Peters D, Leske MC, Bengtsson B. Effects of argon laser trabeculoplasty in the Early Manifest Glaucoma Trial. Am J Ophthalmol. 2011 Nov;152(5):842-8.
4. Leske MC, Heijl A, Hyman L, Bengtsson B, Dong L, Yang Z; EMGT Group. Predictors of long-term progression in the early manifest glaucoma trial. Ophthalmology. 2007 Nov;114(11):1965-72.
Nathan Radcliffe, MD, a glaucoma specialist, is an assistant professor of ophthalmology and director of the Glaucoma Service at Weill Cornell Medical College and New York-Presbyterian Hospital in New York.