Incidence and probability of progression to blindness due to open-angle glaucoma decreases dramatically. Glaucoma is a leading cause of irreversible blindness worldwide. It affects more than 2.7 million individuals age 40 or older in the United States — approximately 1.9 percent of this population. Glaucoma is the second-leading cause of blindness among blacks, after cataract, and the third-leading cause of blindness in whites, after age-related macular degeneration and cataract.