There is a new theory concerning the cause of macular degeneration:
lef.org/Magazine/2008/12/Pre … on/Page-01
The theory goes that the macula actually produces hormones like DHEA and pregnenolone for the eye to use. Macular degeneration occurs when the macula stops producing these hormones and instead produces cholesterol and this build up of cholesterol in the eye causes macular degeneration.