Age-related Macular Degeneration – Written by Associate Professor Lauren Ayton, B Optom, Ph.D., FAAO, FACO.
Age-related macular degeneration (AMD) is a common eye disease in people over the age of 55 years. As the name suggests, AMD is related to ageing (more common in older people) and affects the macula.
The macula is the central region of the retina, the light-sensitive tissue lining the back of our eye. Degeneration of the macula leads to loss of central vision, which affects tasks like reading and face recognition . Even in severe cases, AMD leaves the peripheral vision intact and does not result in “black blindness”.
AMD usually affects both eyes, but it can present differently and progress at different rates between the two eyes. In some people, these changes can be rapid, so you should treat any sudden changes in your vision as an emergency and seek advice from your optometrist or ophthalmologist.
This overview will outline the public health implications of AMD, its causes, the different categories of AMD, its common signs and symptoms, diagnosis, and treatment options, as well as the ways to reduce the risk of AMD.
Globally, it is estimated that 196 million people have AMD, and that this will increase to 288 million by the year 2040 . AMD is the most common cause of irreversible vision loss in people over the age of 50 years, and the fourth leading cause overall .
Approximately 1 in 7 people over 50 years old will show some sign of AMD . However, the progression of the disease can vary significantly between people. Generally, of the people who show early disease, 1 in 7 will then progress to late disease and potentially lose vision from the condition .
For the individual, AMD can lead to a loss of independence, decreased quality of life, and higher levels of depression . At a global level, the economic costs of reduced community participation and healthcare are high. A study in 2010 estimated that the global financial cost of AMD-related vision loss was US$300 billion .
AMD is believed to be caused by a combination of inflammation, oxidative stress and immune responses. There are several known risk factors for the development and progression of AMD.
The chance of developing AMD is 3 times higher in people over 75 years, than those between 65 and 74 years old .
People that smoke are 6 times more likely to develop AMD than those who do not . In addition, smokers develop the disease 5 to 10 years earlier than non-smokers .
A person’s family history such as, whether their parents, grandparents or children have AMD accounts for up to 50% of their own personal risk . There have been over 35 genes identified that are linked with AMD , and these are passed down through families.
A healthy diet, which is high in leafy green vegetables, oily fish and wholefoods (fruits, vegetables, chicken and nuts) has been shown to be protective against the development of AMD . Conversely, diets that have high levels of saturated fats and trans fats (such as highly processed and “junk” foods) have been linked with an increased risk .
AMD is generally categorized into early stages (which are called “early” or “intermediate”) and late-stage disease.
In the early stages of AMD, there are relatively few symptoms. However, late-stage disease leads to complications resulting in significant central vision loss.
There are two forms of late AMD:
In this stage of disease, the light-receptive cells in the retina die. These cells cannot be replaced, and so the retina develops areas of damage, or atrophy. Dry AMD tends to be slowly progressing. There are currently no effective treatments for this form of disease.
In contrast, neovascular or wet AMD usually has a rapid onset. This form of late disease occurs because new blood vessels grow in the retina. These blood vessels are prone to leaking, which can cause bleeding in the eye. Wet AMD can be treated by injections into the eye.
In the early stages of AMD, there are usually few symptoms. Therefore, it is important to have regular eye examinations (at least every two years), as early AMD is often picked up before people start noticing changes in their vision.
Sometimes early and intermediate AMD can cause people to have trouble adapting to different light conditions; for example, walking into a dark room. Some people experience trouble driving at night or reading small print.
In late AMD, the symptoms are more noticeable. The development of atrophic AMD causes gradual loss of central vision. Neovascular AMD causes rapid onset of blurriness, distortion (straight lines look wavy) and loss of the central vision.
People with AMD generally maintain their peripheral, or side vision, even in the late stages of the condition.
If you experience any of these signs and symptoms, schedule an appointment with an eye health professional to get your eyes checked. It is also important to note that the development of eye conditions may even start before symptoms appear, which makes going for regular and timely eye checks that much more essential.
AMD is diagnosed by an eyecare practitioner (optometrist or ophthalmologist), based on the appearance of the retina at the back of the eye.
Sometimes the doctor will take pictures or scans of the retina to assist in diagnosis, or to monitor changes over time. A common form of imaging used is optical coherence tomography (OCT), which is a cross-sectional scan of the retina. This technique allows clinicians to detect areas of retinal damage or bleeding.
If neovascular AMD is suspected, sometimes an ophthalmologist will perform a procedure called a fluorescein angiography. In this test, a coloured dye is injected into a blood vessel in your arm. The dye then travels to the blood vessels in your eye. A special camera takes photos as the dye moves throughout the retina, highlighting abnormal blood vessels or areas of damage.
The treatment for AMD varies depending on the stage of disease.
There are currently no treatments for the early stages of AMD. Your doctor will monitor the condition with regular eye health checks. Sometimes nutritional supplements can help to slow down the progression of AMD – this option should be discussed with your doctor.
There are currently no treatments for the late atrophic form of AMD. However, people with central vision loss can benefit from rehabilitation services that help identify ways to adapt to the changing vision. This can include using magnifiers, improving lighting, and using electronic aids to replace reading on paper.
Neovascular AMD can be effectively treated with injections of anti-vascular endothelial growth factor (anti-VEGF) drugs. For the best outcome, these injections are needed as soon as possible after a bleed in the eye. Hence, it is important that you see your eyecare practitioner as soon as you experience symptoms that may suggest this stage of disease (sudden blurriness, distortion, or loss of central vision).
Whilst two of the main risks of AMD, age and family history, cannot be changed, there are a number of environmental changes people can make to lower their chances of developing AMD.
Quitting smoking is one of the most effective ways to lower your risk of developing AMD. For more advice, speak to your general practitioner.
Aim for 5 or more servings of fruit and vegetables per day, and two or more servings of fish high in omega-3 fatty acids per week, as well as regular consumption of nuts and olive oil.
There are nutritional supplements, called the AREDS formula, which can be beneficial for people who have some forms of AMD. Your eyecare practitioner can advise on the suitability of these supplements for you.
It is very important to see your eyecare practitioner (optometrist or ophthalmologist) regularly if you have AMD, or a family history of AMD.
There are currently clinical trials and research studies underway into treatments for early stages and late atrophic disease, for which there are currently no options. These include new drugs, laser treatments, gene therapy and stem cells. In addition, new anti-VEGF drugs are being tested for neovascular AMD. It is likely that new treatments for AMD will be available in the next 5 years. If you have AMD, it is important to regularly visit your eyecare provider to keep up to date with these advances.
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