This month we will begin focusing on specific eye conditions starting with age-related macular degeneration (AMD). There are two types of macular degeneration: dry and wet. This month we will go over dry AMD followed by wet AMD next month.
What is dry AMD?
As we discussed last month, the macula is the small area in the retina that contributes to our central vision. AMD is a condition that damages this area and can lead to poor central vision. Dry AMD is characterized by the presence of drusen, yellow protein deposits under the retina. It usually affects older individuals and is a leading cause of vision loss in patients over the age of 50.
While dry macular degeneration is the more common type, it causes less vision loss. It is categorized by three stages: early, intermediate, and advanced. Even with some signs, not everyone progresses to later stages of the disease.
What puts people at higher risk of developing AMD?
Older age: The risk of AMD increases with age.
Caucasian race: This condition predominantly affects those with a Caucasian background versus African American and Hispanic. According to the National Eye Institute, in 2010, 89% of people in the U.S. with AMD were Caucasian (https://www.nei.nih.gov/eyedata/amd).
Family history: Patients are at a higher risk if a relative has had the condition. There are several genes that contribute to AMD.
Smoking: Research has shown that smoking increases risk of developing AMD.
High blood pressure and cholesterol: These are shown to be risk factors for developing AMD.
What are the symptoms?
AMD can cause changes in central vision which include blurry vision, distorted vision, or darker central vision. It may also cause loss of vision. It does not cause any pain.
How is it detected?
AMD is diagnosed with a comprehensive eye exam including checking the vision and dilating the eyes to view the retina and look for drusen. The number and size of the drusen allows us to determine the stage of AMD. Many people will develop some small drusen with age, but more numerous and larger drusen can be a sign of AMD. Doctors also look for color changes, or pigmentary changes, in the retina that arise from the breakdown of cells in the pigmented layer of the retina.
The early stage is characterized by the presence of some drusen which do not usually affect vision. The intermediate stage shows more drusen, larger drusen, and/or pigment changes and can affect the vision. Advanced stages have drusen and geographic atrophy, loss of retinal tissue, that cause vision loss.
There are several photos that are taken to aid in the diagnosis. These include optical coherence tomography, OCT, and fluorescein angiography, FA. OCT takes a cross sectional photo of the retina and provides a view of all the layers to look for drusen. FA involves an injection of dye into a vein in the arm and taking photos of the eyes as the dye goes through the blood vessels. It helps in the diagnosis of the wet form of macular degeneration (more on this next month).
What are the treatments?
Unfortunately, there is no cure for AMD but there are some steps patients can take to slow its progression.
AREDS vitamins: The National Eye Institute conducted research to investigate if supplements would protect against AMD. It found that these supplements slowed the progression of AMD in patients with intermediate AMD and those with advanced disease in one eye. The formulation includes vitamin C, vitamin E, zinc, copper, lutein, and zeaxanthin.
Amsler grid: This is used to monitor the disease at home. Patients check this grid on a daily to weekly basis depending on the stage and condition of both eyes. The lines on this grid should appear straight while looking at the central dot. If there are any distorted, wavy, or missing lines this may be an indication that the disease is progressing and warrants a visit to the ophthalmologist.
Low vision tools: There are many aids to help patients with poor vision from AMD including magnifiers, high-powered lenses, large print materials, talking clocks and calculators, closed-circuit televisions, and other computer-based aids.
Lifestyle changes: Smoking is a known risk factor for worsening this condition, avoiding it can help to reduce the risk of AMD. Incorporating more green leafy vegetables and omega-3 in the diet are beneficial. Maintaining normal blood pressure and cholesterol levels are also helpful.
Return next month for our discussion of wet AMD.