Both forms of AMD start from the same disease and result when drusen(waste products) form beneath the macula. The number and size of drusen increase leading to a progressive loss of central vision over time.
As the disease progresses the drusen reduce the nutrients flowing to the retina, the retina becomes very thin and fragile new vessels grow in between the cells.
These vessels can leak, hence in 10% of cases of dry AMD becomes wet AMD. This can lead to a sudden aggressive loss of vision and is treated treatment is via the injection of anti vascular endothelial growth factor (anti-VEGF) drugs. These drugs inhibit the formation of the new blood vessels in the eye.