Age-related macular degeneration is a common condition of the eyes in older persons. It is the most common cause of loss of vision in people who are age 50 or older. Age-related macular degeneration is commonly referred to as AMD. What AMD does is damage the centre of the retina in the back of the eye. This part of the retina is called the macula. It is the most important part of the retina because it is where we see things that are directly in front of us and where we have our sharpest and clearest vision.
AMD often progresses quite slowly so that people do not recognize that they are losing vision until it becomes advanced, they fail a vision test for driving or realize that they can no longer recognize faces or that things appear less bright than they used to. At its extreme, the blurry area caused by AMD becomes a blank spot in the centre of the visual field. AMD can also advance much more rapidly. In either case, we urge our patients to treat this condition as soon as it is recognized.
The blindness caused by AMD is not complete and will not necessarily be equally bad in both eyes. Peripheral vision is spared. But, doing any close work, reading, writing, watching the television or a computer screen, cooking, or doing the basic chores of everyday life becomes increasingly difficult.
Our central vision is sharper than our peripheral vision because the macula has more retinal cells that sense light. Signals from the macula go to the brain via the optic nerve and the brain constructs the images that we “see” or experience. When the cells in the macula are damaged, they quit sending signals and what we see becomes dark, blurred, and distorted. Because the macula has most of the colour-sensitive cells (cones) in the retina, AMD robs individuals of their colour vision.
There are 5 things that increase your risk of getting AMD or of your AMD getting worse.
If AMD shows up in your family tree, you are more likely to develop the condition. However, at current count, there are nearly two dozen genes that affect your risk of getting AMD and researchers are steadily finding more every year. So, genetic testing is not very useful in predicting whether or not you will have this eye disease.
From a genetic viewpoint, you are at higher risk of getting AMD if your ancestors came from Europe, North Africa, the Horn of Africa, Western Asia, Central Asia, or South Asia.
Smoking doubles your risk of getting AMD. If you are a Caucasian with a family history of AMD, this is just one more reason to quit smoking.
Patients with diseases of their heart or blood vessels have a higher risk of AMD.
Obese patients have a higher risk of mild AMD progressing to a severe stage.
The first thing that you can do if you are concerned about this disease is to ask us for a complete eye exam. AMD is visible when we use special equipment to look at the retina at the back of the eye. Specific tests include these:
If your examination shows indications of AMD, or if you have a strong family history, there are several things that we can do depending on the type and stage of AMD that you have.
AMD has three stages. We will determine if you have AMD and its stage by the presence of yellowish deposits called drusen under the surface of the retina as well as excess pigmentation under the retinal surface. Drusen are deposits of extracellular waste that accumulate under the retina, between a specialized layer of cells called the retinal pigment epithelium (RPE) and Bruch’s membrane, a meshwork of fibrous proteins (mostly collagen). The RPE helps maintain the photoreceptors (the light-sensing cells that make up the bulk of the retina), transporting nutrients and wastes between the photoreceptors and the blood vessels that supply them. By age 60, changes take place that can cause drusen to build upon Bruch’s membrane, which displaces the RPE and forces the two layers apart. Such disruption to the RPE can damage the photoreceptors. An increase in the number or size of the drusen increases the risk of age-related macular degeneration.
At this stage, we will see drusen deposits of medium size (roughly as wide as a human hair). The patient will rarely complain of visual loss and we will find a normal vision on testing.
Patients at this stage have pigment changes, large deposits of drusen or both of these. Although the patient will typically not complain of visual loss, we will find problems on our exams.
Besides having large drusen deposits, late stage AMD patients experience loss of vision and problems in their everyday lives. There is obvious damage to the macula on examination. At this point, AMD breaks down into two types which is important for treatment.
Roughly 9 out of 10 patients with AMD have the “dry” form. They have deposits of drusen, their macula thins, and they will experience some degree of visual loss or problems with their central vision. This thinning of the retina can appear to your doctor with a microscope like a geographic shape, hence the name. This form can also progress to the “wet” form.
This is the severe form of the disease and we will see blood vessels growing under the retina (Neovascular = new blood vessels). There is often fluid leaking from these vessels with subsequent swelling and macular damage. In this form, AMD may progress very rapidly.
There are first things that everyone with even the lowest stages AMD should do.
Not everyone with mild, early AMD goes on to the later stages. Routine eye exams are necessary to track the disease and institute therapy if and when the disease starts to progress. Without therapeutic intervention, 5 percent of people with early stage AMD in just one eye will go on to the advanced stage within 10 years. If both eyes have early stage AMD, 14 percent have advanced AMD within 10 years.
There is no proven treatment for the early stages of AMD but instituting the lifestyle and dietary changes can make a huge difference!
If your disease has progressed to the intermediate or advanced stage, you can and should be taking specific dietary supplements and vitamins. Two comprehensive scientific studies, AREDS and AREDS2, demonstrated that taking the following every day significantly reduces the progression of the disease.
The loss of vision in advanced stages of this disease is caused by the growth of and leaking of new blood vessels. We can treat (but not cure) this disease with three approaches.
There are chemicals (medications) that slow or stop the formation of new blood vessels behind the retina and specifically the macula. These are injected directly into the affected area. After anesthetizing the eye, we will inject an anti-VEGF drug. Although it often takes a couple of injections to get used to this, it is not painful due to the anesthetic. VEGF (vascular endothelial growth factor) promotes (in this case) excessive blood vessel formation and anti-VEGF therapy blocks this. These injections are repeated regularly to help keep the disease from progressing. There are several of these medications. We will choose the one that is best for your situation.
This laser treatment is used to target very specific areas of new blood vessel growth under the macula and other areas of the retina. We inject the drug verteporfin into your arm. When it passes through the eye, it will be absorbed by the new and growing blood vessels that are part of AMD. Then we shine a laser beam on the blood vessels. This activates the drug, causing it to close off just the blood vessels that are causing your problems. This is not a “hot” laser and only serves to activate the drug. This therapy is the second most common for AMD after anti-VEGF therapy.
This is where we will cauterize selected blood vessels with intense heat from a laser. We typically use this treatment for small areas of blood vessel growth that are away from the macula as the treatment burns the retina and causes a small blind spot as a way of preventing a larger blind spot later on. This is the least common method that we use to treat AMD.
At times we use steroids as an adjunct to other treatments, but these need to be used carefully as they can raise the pressure inside the eye, cause glaucoma, and damage the retina.
Originally used as an anti-cancer drug, this medication has an “off-label” use in treating AMD similar to anti-VEGF therapy.
At Orbit Eye Centre we treat patients and not just their eyes. As such we routinely help our patients who have lost vision with a visual rehabilitation approach. Many devices that can help those who have lost vision due to AMD.
The results of undiagnosed and untreated AMD can be devastating. The first and most important thing that you can do is have your eyes examined. If you have signs of early AMD, it is essential that you continue your examinations and follow our instructions regarding changes in diet, stopping smoking, and exercising. If, and when, it is appropriate, will institute specific, proven therapies to slow or stop the progression of your AMD.