The most common forms of this disease usually affect patients over the age of 65 and are collectively the most frequent cause of legal blindness in developed countries. Age-related macular degeneration is extremely prevalent, with as many as one in 10 patients over the age of 65 affected to some degree. Fortunately, severe visual loss is much less common, affecting perhaps one in 100 people over the age of 65. The inside of the eye is lined by three layers of tissue, each critical for normal vision.
Light enters through the cornea, passes through the pupil and the lens and strikes the retina.
The RPE provides metabolic support for the photoreceptor cells and also removes old bits of cellular debris from the tips of the photoreceptor cells as they renew themselves. The layer farthest from the incoming light is a rich network of blood vessels known as the choroid. These vessels supply oxygen and nutrients to the retinal pigment epithelium and photoreceptor cells and carry away waste products. With the passage of time, patches of retinal pigment epithelial cells may die, resulting in bare spots known as geographic atrophy. When the support functions of the RPE are lost, the photoreceptor cells overlying the areas of geographic atrophy cannot function and the vision from this patch of retina is lost.