Types of age-related macular degeneration (ARMD)
- Dry age-related macular degeneration (dry-ARMD). This is a very common type of ARMD and happens in nine out of ten cases. The cells in the macula of the retinal pigment epithelium gradually become very thin or the cells experience atrophy and then degenerate. This cellular layer is very important for the rods and cones to function normally. If the cellular layer dies, the seeing cells will also degenerate then die. Dry-ARMD is a very gradual and slow process as the amount of infected cells increase. It would normally take several years to have the vision seriously affected. But many of the patients who have dry-ARMD do not lose the reading vision.
- Wet age-related macular degeneration (wet-ARMD). This type of ARMD happens in one out of ten cases. Although quite rare, this type causes severe visual impairment in just a few short months. In wet-ARMD, aside from the cells of the retinal pigment becoming degenerate, new small blood vessels begin to grow from small blood vessels located in the choroid. This development of new blood vessels in the choroid is also known as choroidal neovascularization. The newly formed blood vessels break the Bruch's membrane until the macular portion in the retina. These newly formed blood vessels are not really normal because they are very fragile and have the tendency to leak fluid and blood. This event could scar the macula and damage the rods and cones.