In the early and intermediate stages of AMD, waste products from the retina accumulate underneath the retinal pigment epithelium (RPE). These waste produces are known as drusen, and appear as fatty, yellow deposits. People with early and intermediate AMD typically have little or no impact on vision. However, the presence of drusen increases the likelihood of progression to late-stage AMD and vision loss.
About 85% of people with AMD have early/intermediate stage disease, which has little or no impact on vision.
Early/intermediate AMD can be classified based on the size of drusen, with or without accompanying changes to the RPE, which is the barrier between the choroid and the retina that is responsible for maintaining and nourishing the retina.1
In its late stages, AMD and can result in major vision impairment, including legal blindness. About 15% of people with AMD have late-stage disease.
Late-stage AMD is further divided into two forms:
Also known as geographic atrophy, dry AMD is characterised by the presence of drusen and by a breakdown or thinning of Bruch’s membrane. This normally results in a gradual loss of vision over many years. At present, there are no medical treatments for dry AMD. About one-third of people with late AMD have the atrophic dry form.
Neovascular or “wet” AMD occurs when the blood vessels from the choroid grow into the retina. This growth is called choroidal neovascularisation (CNV). The rapidly growing, fragile vessels leak blood and fluid, leading to scarring of the retina, which results in permanent vision loss. Wet AMD is the most severe form of the disease and is associated with sudden and severe changes in vision. About two-thirds of people with late AMD have the wet form.
Ferris FL et al; Clinical Classification of Age-related Macular Degeneration. Ophthalmology 2013;120:844-851.