Visual loss is often considered the most feared complication of human disease, other than death. In 2002, 124 million people worldwide had poor vision and 37 million were blind.¹ In developed countries, the primary causes of visual loss are age-related macular degeneration, in the elderly, and diabetic retinopathy, in working-age persons. It is estimated that diabetes mellitus affects 4 percent of the world's population, almost half of whom have some degree of diabetic retinopathy at any given time. Visual loss primarily occurs from either proliferation of new retinal vessels (proliferative diabetic retinopathy) or increased permeability of retinal vessels (diabetic macular . . .