Age-related macular degeneration (AMD) has two forms – wet and dry – and is labeled according to the way in which the macula is damaged.
In dry AMD, the macula begins to break down as the tissue that supports the photoreceptors – the rod and cone cells – thins and loses pigment. These changes, which often occur in both eyes at the same time, cloud central vision and distort color perception. At this stage, however, the condition is not characterized by leaking blood vessels. Thus, it’s called dry AMD.
Dry AMD has three stages, all of which may occur in one or both eyes. The occurrence of dry AMD in one eye dramatically increases your risk of developing it in the other eye. In 10 to 20 percent of the people with early or intermediate stage dry AMD, the disease progresses to advanced dry AMD. This stage is characterized by a round, well-defined, nearly transparent spot etched into the macula. This spot is called an area of geographic atrophy.
All people who have wet AMD had the dry AMD first. The dry form can advance and cause vision loss without turning into the wet form. The dry form also can suddenly turn into the wet form, even during early stage AMD. Dry AMD evolves into wet AMD in one out of every seven people with the disease. There is no way to tell if or when the dry form will turn into the wet form.