Macular degeneration is the leading cause of vision loss, irreversible vision loss in the United States and actually in patients over the age of sixty-five and in fact in all industrialized nations. It's not the leading cause of vision loss in the world because in underdeveloped nations there are other preventable causes such as infectious diseases and glaucoma and so forth. But at least in the United States, Canada, Western Europe, Japan, and most of the industrialized world, this is the leading cause of blindness. If you look at the American population from an epidemiologic standpoint, there are about eight million Americans that have some form of this disease in some moderate degree. About somewhere in the vicinity of about 1.2 million have very severe vision disability, meaning that they are legally blind as a result of this condition. Approximately one hundred and eighty thousand to two hundred thousand Americans every year develop this condition.

Mark Blumenkranz is a professor and the chairman of the department of Ophthalmology at the Stanford University Medical Center.