People who smoke, or have smoked a large number of cigarettes over time, are more likely to develop age-related macular degeneration or to have it worsen sooner, according to a long-term study.

Age-related macular degeneration (AMD) is a common eye disease that results in damage to the central part of the retina and is a leading cause of blindness among Americans over the age of 50.

The current theory is that smoking might damage blood vessels that nourish the retina, leading to an increased risk of worsening of macular degeneration, or that smoking might deposit toxins within retina tissue that damage its functioning.