The most common -- and under-diagnosed -- genetic disease in humans just may be a cause of the worst form of macular degeneration, researchers report. They are pursuing a link between hemochromatosis, which results in iron overload, and the wet form of macular degeneration, the leading cause of blindness in people 60 and older. They suspect that too much iron, known to wreak cumulative havoc on the body's organs, hastens normal aging of the eyes.