By Dr. Alanna O’Keefe, OD
What is it? Age-related macular degeneration affects about 15 million people in the United States. Inside our eye, we have a layer called the retina that uses the light coming into our eyes to send signals to our brain. These signals are then turned into images. Near the center of the retina is a small portion called the macula, where AMD occurs. This is important because the macula is responsible for our central vision, which is also our sharpest, and clearest vision.
AMD can be broken down into multiple categories, but there are two main forms. Dry AMD (nonexudative) is due to yellow deposits beneath our retina called drusen, or changes to the pigment in the retina. These changes can cause damage to the light-sensitive cells in the macula. This causes the visual information sent to the brain to be inaccurate, resulting in decreased vision. The other form is known as wet AMD (exudative or neovascular AMD). This is where abnormal blood vessels grow underneath the retina. These blood vessels cause leaking of blood or fluid, which will damage the macula. It is important to note that both eyes may not have the same type of AMD and they can progress at different rates.
Who is at risk? People over 60 are at an increased risk of AMD, however, it can occur earlier. Smokers have double the risk of developing AMD. It is more common among Caucasians and tends to occur earlier in women. Family history does play a role and there have even been links to obesity, high blood pressure and elevated cholesterol. Genetic testing is currently available to determine patients who are at risk of AMD. Genetic testing is new and not widely used at this time. This is due to the fact that it is costly and currently has no effect on the outcome or treatment of the disease.
Symptoms In the early stages of dry AMD, patients are usually without symptoms. Mild changes can appear as the need for more light when reading, difficulty in low lighting, blurriness when doing detailed near work, colors not appearing as bright, blurred central vision, or blank/black spots in the central vision. If wet AMD is present the symptoms can appear rapidly. A sudden decline in central vision can be noted or straight lines can appear wavy or distorted.
How is age-related macular degeneration detected? A dilated fundus exam by an optometrist or ophthalmologist is the easiest way to evaluate for AMD. They may also ask you to look at an Amsler Grid (pictured below). This will be done to see if any of the lines are missing or distorted. If wet AMD is suspected they may use additional testing to determine if there is any blood or fluid in the retina. An optical coherence tomography (OCT) will use light to provide a cross section through the retina. A fluorescein angiogram (FA) will inject fluorescent dye into your arm that will then go through the blood vessels of your eye and when pictures are taken will show leaking blood vessels.
What to do? One of the easiest things to do is to ensure a healthy lifestyle. Avoid smoking, exercise regularly, maintain normal blood pressure and cholesterol levels, and eat a diet rich in green leafy vegetables and fish. This has been the best advice for early dry AMD as there is no effective treatment available.
For those who have wet AMD there are different treatments that will not cure, but can help slow further vision loss. Laser surgery can be used to get rid of the abnormal blood vessels. Photodynamic therapy is when a medicine is injected into the arm and is then triggered by a laser to destroy the abnormal blood vessels. The most widely used treatment at this time is injections of medicine into the eye that will destroy the abnormal blood vessels in the eye.
Extensive research has been done by the National Eye Institute to see whether or not high-dose vitamins and minerals can help protect the eye in patients with AMD.
Studies showed that certain high-dose vitamins did slow the progression of the disease, but only in certain stages of AMD. There has also been recent debate with the advancement of genetic testing as to whether or not these vitamins are beneficial for all people. These studies are ongoing and due to the variability in the research it is important to ask your doctor for advice before starting a high-dose vitamin regimen for AMD.
The FDA recently approved an implantable telescope about the size of a pea for people who have end-stage AMD in both eyes and are over 65. This will enlarge the central image over a larger area of the retina. This will improve the central vision in the treated eye, but is not a cure. It is important to note that while there is no cure for AMD even patients with late stage changes can lead very productive and rewarding lives. It is important for these patients to have referrals to low vision rehabilitation specialists who can help them get special devices and resources to ensure their independence.