AMD, neovascular

It is common for the macula to break down as one ages. Sometimes, the deterioration of the macula, as well as a predilection to risk factors such as heredity, race (whites are more susceptible than people of darker pigment), smoking, or a high-fat, low-antioxidant diet leads to Age-related Macular Degeneration (AMD). 

Neovascular AMD describes the formation of new fragile capillaries in response to extensive damage and breakage of the pigment epithelial layer of the macula. Damage to this thin, mesh-like layer of capillaries may occur because of the presence of drusen or because of fluid accumulating in the sub-retinal space between the two layers. 

Instead of forming in an organized fashion, the new blood vessels messily make their way into sensory layers of the macula. These new vessels often break as well, and along with the broken vascular layer, destroy the healthy macula.

Most, but not all, people with wet AMD have neovascular AMD. Combined, wet AMD and neovascular AMD account for only 10% of all cases of AMD. Unfortunately, these cases also account for the most severe loss of vision. 

For both groups, leakage of blood and other fluids into the macula causes extreme blurriness and even dark “blobs” in the center of vision. Over time, reading and other pastimes requiring detailed, straight-ahead vision will be affected. However, total blindness does not normally occur, since AMD only affects central vision.

Technologies like fluorescein angiography (FA), indocyanine green (ICG) imaging, and ocular coherence tomography (OCT) are able to determine where new blood vessels are wildly and uncontrollably proliferating. The location determines the type of neovascularization and is also the determining factor for treatment.

There are a number of very effective treatments available, mostly targeting the new blood vessels that form in response to the broken layer between the retina and the choroid. There are currently three anti-vegf agents, Macugen (pegaptanib), Lucentis (ranibizumab), and Avastin (bevacizumab), that are used to prevent new, fragile blood vessels from growing back. Additionally, laser photocoagulation and photodynamic therapy work in slightly different ways to seal off broken vessels or destroy new, unhealthy ones.