This month we will continue our discussion about age-related macular degeneration focusing on wet AMD.
What is wet AMD?
As we discussed last month, macular degeneration affects the central region of the retina called the macula. Wet, or neovascular, AMD is less common than dry AMD but can have a profound effect on vision. Wet AMD is characterized by the growth of abnormal blood vessels below the retina known as choroidal neovascularization, CNV. These vessels can leak leading to the presence of fluid or blood in the retina. This disruption of the normal retinal architecture causes vision changes. Ultimately, the CNV can cause scarring that may result in permanent vision loss.
What puts people at higher risk of developing AMD?
The risk factors for wet AMD are the same as for dry AMD:
- Older age
- Caucasian race
- Family history
- Smoking
- High blood pressure and cholesterol
What are the symptoms?
Wet AMD can present with blurry vision, distorted vision, or dark central vision as is the case with dry AMD. Howerver, wet AMD often presents with sudden vision changes or vision loss instead of gradual visual changes. There is no pain associated with AMD.
How is it detected?
A comprehensive exam including checking the vision and dilating the eyes to view the retina are imperative to diagnose wet AMD. As with dry AMD, ophthalmologists search for yellow deposits called drusen. However, with wet AMD, physicians want to identify disruption of the retina from the choroidal neovascular membrane, CNVM. Blood and fluid may be present on exam as well. The following photos show various presentations of wet AMD.
CNVM in wet AMD. Image Source 1
Blood and fluid from a CNVM. Image Source 1
Blood from a CNVM. Image Source 1
In advanced stages, the CNVM may cause scarring that leads to vision loss.
Wet AMD with scarring. Image Source 1
The photos to aid in the diagnosis of wet AMD are optical coherence tomography, OCT, and fluorescein angiography, FA. OCT takes a photo of the layers of the eye to look for the CNVM. FA involves injecting a dye into the arm and taking photos as the dye goes through the blood vessels in the eyes. When there is a CNVM, the dye leaks from the abnormal vessels. This can be seen in the following photo.
FA showing leakage from a CNVM. Image Source 1
What are the treatments?
Although there is no cure for AMD, there are some treatments that help to resolve the leakage from the CNVM in wet AMD and can reduce vision loss.
Laser: Laser used to be the main treatment for wet AMD. Photodynamic therapy, PDT, is where the medication verteporfin is injected into the bloodstream. A laser beam is used to activate the medication and close off the abnormal blood vessels in the retina. Photocoagulation also uses a laser to treat the abnormal blood vessels and prevent them from bleeding.
Injections: These are now the most common treatment for wet AMD. The injection is given into the affected eye. The medications used are anti-VEGF medications. VEGF, vascular endothelial growth factor, is a normal compound in the body that regulates the growth of blood vessels. In wet AMD there is too much of this compound, and the drugs block the effects of VEGF and shrink the network of abnormal blood vessels. There are several regimens used by doctors when treating with injections, but most patients are started on monthly injections and then screened for additional injections.
Patients with wet AMD should also follow the treatments of dry AMD. This includes taking AREDS vitamins and lifestyle changes such as not smoking and maintaining a healthy diet. An Amsler grid should be used to monitor changes in vision and low vision tools can be helpful for patients who have advanced disease and vision loss.
Return next month for a discussion on a new topic!