There are two types of late onset Macular Degeneration: "dry" AMD and "wet" AMD.

Dry AMD is the more common form. It is also referred to as atrophic, nonexcudative, or drusenoid form. This form accounts for 90 percent of Age-related Macular Degenerations.

Dry AMD is characterised by the build-up of drusen, small yellowish deposits, beneath the macula. The layer of photo receptor cells in the macula begin to atrophy, or die, as some of the cells break down. These changes, may, in turn, result in a distortion of vision that is most apparent when reading. Often if one eye has dry AMD, the other eye will also show some signs of the condition. However, dry AMD does not usually cause total loss of reading vision.

Wet AMD accounts for 10 percent of patients with AMID. It is also called choroidal neovascularisation, subretinal neovascularisation, exudative form, or disciform degeneration.

In wet AMD, new abnormal blood vessels begin to grow beneath the macula, in a thin layer of tissue called the choroid. The choroid is the main source of oxygen and nutrients for the retinal photo receptors, and it is the only blood supply for the macula. New fragile blood vessels develop which may leak fluid and blood, and then cause the choroid and retina to deteriorate. This causes the retinal layer to blister under the macula, and the photo receptor cells to degenerate. At this stage, there is marked disturbance of vision in the affected eye.