Age-related Macular Degeneration (AMD) is a poorly understood condition affecting many Canadians
This summary has been developed to meet the needs of people who may be at risk of developing AMD and for those who have recently been diagnosed with it. There are five sections:
Introduction to AMD. General information about AMD that everyone should know.
Risk Factors. For everyone, but especially if you are over 45 years of age because you’ll soon be in the age-group that is susceptible to developing AMD.
What is Dry AMD? A brief explanation of the most common form of AMD.
What is Wet AMD? A simplified explanation of a very complex disease.
Living with AMD. Practical information and tips for anyone living with AMD.
As its name suggests, Age-related Macular Degeneration is a disease linked to age. Specifically, people over age fifty.
In spite of the fact that AMD is the leading cause of severe vision loss and legal blindness in people over 50 in the Western world, AMD is still relatively misunderstood. Knowledge is power. Take a few minutes to learn about AMD – it may help you in the long run.
Introduction to AMD
AMD is a chronic, age-related, degenerative disease of the macula. The macula is a very small and specialized area in the centre of the retina. The macula allows you to see fine details directly in front of you such as words in a book or images on television. So while the entire retina lets you see that there is a book in front of you, the macula lets you see what is written in the book.
Generally speaking, dry AMD progresses quite slowly and is usually less severe than the wet type. But both types damage the macula and both can take away your central vision, which means the images you see directly in front of you.
With impaired central vision, you might not be able to do some of the things you normally take for granted, like reading, driving, a favourite hobby and more.
Because AMD affects only your central vision, you won’t ever be totally blind. You will still have your peripheral, or side vision. Most people are able to maintain independence if the condition is not too advanced.
Early detection and intervention is key to preventing or delaying vision loss. In the case of dry AMD, unless it’s detected in a routine eye exam, you may not even realize that you have the disease until it reaches an advanced stage. This is due to its usually slow and painless progression over a period of years, and the ability of one eye to compensate for any weakness in the other eye.
Generally most patients start out with dry AMD, which slowly progresses over many years. About 10% of all dry AMD cases go on to develop wet AMD. Wet AMD worsens much more quickly than dry AMD causing severe and irreversible central blindness, often within months, sometimes even weeks. All of this makes a strong case for visiting your eye doctor regularly, especially if you determine that you’re at risk.
There are a number of factors both in and out of your control that can put you at increased risk for developing AMD. Knowing what they are might inspire you to make certain lifestyle modifications that can help to reduce that risk. Some of the known and suspected risk factors that you can’t do anything about are:
Age: Risk increases with advancing age; from 8.5% for people 43–54 years of age to a high of 36.8 % for people over 75
Family history of AMD
Gender: Females are more susceptible
The following are risk factors that you can do something about:
Diet: A diet low in antioxidant vitamins and minerals is a significant risk factor
Excessive sunlight exposure
High blood pressure
Obviously you can’t change everything that puts you at risk, but wherever you can, consider making any lifestyle changes that will reduce your risk.
Most of the time, AMD will begin as the less severe dry type and, for 85–90% of people, it will remain that way. Dry AMD can develop in one eye or both.
The early stage of dry AMD usually begins with the appearance of drusen. Drusen are small white or yellowish deposits that begin to accumulate in one of the deepest layers of the retina due to a breakdown in its normal function. You will not be aware that these deposits are forming.
As the retinal layer continues to break down, an abnormal amount of drusen begins to build up. This build-up begins to disrupt the layers above it, eventually damaging the layer of photoreceptor cells (the cells that receive visual images from the lens), resulting in “blank” or blind spots in your central visual field.
As dry AMD progresses from early to late-stage, more cells break down and begin to waste away. At the same time, drusen continue to build up and eventually, additional, larger blind spots are formed.
As the disease continues to progress, the likelihood of it turning into the more severe wet AMD significantly increases as well. According to the Age-Related Eye Disease Study (AREDS), a large North American study of the effects of vitamins on dry AMD, up to 43% of people with late stage dry AMD can progress to the even more aggressive wet form of AMD within five years.
With this type of prognosis, it’s important to be proactive and do everything possible to slow the progression of the disease. Your eye doctor will work with you to develop a plan to do just that. What’s most important is keeping all of your scheduled check-ups because monitoring the progress of AMD can be one of the best defences against severe vision loss.
Diagnosis of Dry AMD
Dry AMD might first be noticed during a routine eye examination by your eye doctor, or you might have made a special appointment because you noticed that something odd was happening to your vision. Either way, an official diagnosis of AMD should be left to an optometrist or ophthalmologist.
Since dry AMD develops quite slowly, it can affect the vision in your eye without you being aware of it.
That’s because your eyes and brain are very good at compensating for weaknesses. So if AMD is compromising vision in one eye, the good eye will adjust, making up for the other’s deficiency. Regular visits to your eye doctor are critical for early detection and the preservation of your vision.
Treatment of Dry AMD
Treatment of dry AMD is focused on monitoring and slowing the progression of the disease. Your eye doctor will want to monitor your progress at specific intervals in his office, and you will also be told to monitor your vision at home with an Amsler Grid. You should also consider making any modifications to your lifestyle that will help to slow the progression of the disease. Your eye doctor will discuss all of these options with you.
Perhaps the most important thing you can do is heed your doctor’s advice about vitamin supplements. Specific high-dose ocular vitamin therapy as outlined in the ARED Study has been shown to delay the progression of dry AMD in 80% of the population. Unfortunately for as many as 20% of the population AREDS vitamins have been shown to have no effect and may in fact increase the progression of dry AMD to wet AMD. This is because of the incompatibility of certain people’s genetic makeups with ingredients found in AREDS vitamins like zinc.
Carotenoid antioxidants including lutein, zeaxanthin and meso-zeaxanthin have been shown to be beneficial in protecting against AMD.
The Amsler Grid
The Amsler Grid is a useful and simple tool for monitoring your central vision. It’s a test that you can do at home.
Its regular use will alert you to any changes in your vision.
How to use an Amsler Grid (repeat for each eye):
Note: if you wear reading glasses, be sure to have them on whenever you take this test.
Position the grid at a comfortable reading distance
Look at the centre dot on the grid with one eye at a time, covering the other eye with your hand
Make sure you stay focused on the centre dot
As you continue to look at the centre dot, check to see that all the surrounding lines are straight and all the squares are the same size
If any area on the grid appears blurred, distorted, discoloured or in any way abnormal or different from your last test, contact your eye doctor immediately
Wet AMD is so named because of the involvement of blood in the deepest layers of the retina. In a process called choroidal neovascularization (CNV), new and abnormal blood vessels spontaneously begin to grow beneath the retina and push their way up through it.
Imagine they’re like tree roots or weeds growing up through cracks in the pavement. Being weak and abnormal, these new vessels leak their contents of blood and fluid into the retina which separates and lifts up the other layers like a blister. This process finally disrupts the photoreceptors (the cells that receive visual images from the lens), leaving them unable to transmit visual signals to the brain. This results in “blank” or blind spots in the central visual field.
Left alone, this process eventually results in the growth of scar tissue which, in turn, causes severe and permanent central vision loss. Perhaps surprisingly, there is no pain associated with the entire process.
Although wet AMD can occur spontaneously, it’s usually preceded by dry AMD, which makes regular check-ups especially important. Wet AMD is more aggressive than dry AMD and does not occur as frequently, accounting for approximately 10–15% of all AMD cases. It can cause rapid, severe and permanent central vision loss in a matter of weeks. Early detection is critical in order to start any treatments that might help preserve your vision.
Types of Wet AMD
There are various types of wet AMD that have been named after the type or pattern of leakage that is present in the retina. Some of these types respond to treatment better than others. Only an eye doctor who specializes in AMD can determine which type you have and how it should be treated.
What are the Symptoms of Wet AMD?
Straight lines appear wavy or distorted (metamorphopsia)
Blank spots in central vision (scotoma)
Any combination of the above
You will probably be the first person to detect the onset of wet AMD when you notice that your vision has suddenly changed. If you already have dry AMD, you might first notice a change on your Amsler Grid test. If you’re not aware that you have any kind of AMD, your vision might suddenly blur, you may see a blank spot in your visual field, or things that should be straight appear bent or wavy.
Often accompanying the distortion and vision loss is a decrease in contrast sensitivity, which is the inability to distinguish dark from light as pictured. A loss of colour perception is also part of AMD.
Will I Lose My Vision Completely?
No. However the eventual outcome of untreated wet AMD can be severe and permanent central vision loss, with vision dropping to legal blindness or lower. In AMD, total blindness or darkness almost never occurs because the disease does not affect the entire retina, just the central macula. So while someone with AMD may experience extremely poor vision in their central visual field, their peripheral vision is not impaired.
How Fast Does it Progress?
Unlike dry AMD which progresses relatively slowly and may go unnoticed for years, wet AMD is more aggressive and can cause severe vision loss in a matter of weeks or months. The speed at which wet AMD progresses is dependent on a variety of factors. And once you have wet AMD in one eye, the chances of it developing in your other eye are significantly increased.
How is it Diagnosed?
Your regular eye doctor can usually detect the presence of wet AMD based on your symptoms, medical history and a basic eye including a dilated retinal exam and OCT scan of the retina. That’s why regular eye exams are important because early diagnosis gives you a better chance at preserving more of your vision.
If your regular eye doctor suspects wet AMD, you will be referred to a specialist who will recommend and perform a specific course of action personally tailored to you.
How is Wet AMD Treated?
Current treatments for wet AMD include a series of injections into the eye with a special medication called Anti-VEGF. Anti-VEGF treatments are a group of medicines which reduce new blood vessel growth or edema (swelling). Your specialist will recommend the best treatment for the type of wet AMD that you have. You should be aware however, that the goal of treatment is to delay or halt disease progression, they do not always restore vision already lost to the disease.
You should also be aware that treatment of wet AMD is a process that involves you, your eye doctor and your AMD specialist working together to slow down and limit the amount of vision loss. Because wet AMD is a chronic disease, constant monitoring of your progress is essential.
That means doing your Amsler Grid tests as directed and keeping all scheduled appointments, whether for a check-up or additional treatments.
It’s Your Vision – Hold on to it
Your vision is precious – do whatever is in your control to hold on to it. While some degree of vision loss is inevitable with AMD, there are specific things you can do that may help to delay it:
Visit you eye doctor or AMD specialist regularly – do not miss any scheduled appointments
Take the specific ocular vitamin supplements recommended by your eye doctor
If you notice a change in your vision or your Amsler Grid test, contact your eye doctor immediately
Stop smoking – ask for help if you need it
Improve your diet – include more fresh fruits and vegetables, especially dark green leafy vegetables like spinach
Maintain a healthy body weight
Avoid excessive exposure to direct sunlight – wear sunglasses and wide-brimmed hats to protect your eyes from UV light
Keep high blood pressure under control
Be proactive about vision rehabilitation and the use of visual aids
Living with AMD
A diagnosis of AMD does not mean an automatic sentence to a life of blindness, however, the disease can have a profound effect on your quality of life. A significant loss of central vision can severely impact your ability to function as before, making things you’ve always taken for granted such as reading, driving, and watching television, extremely difficult. But, since your peripheral vision is not directly affected by AMD, you should still be able to function independently with the help of visual aids and rehabilitation.
One of the most difficult things to overcome however is the emotional toll that vision loss takes. On the first diagnosis, people can experience a range of emotions including shock, disbelief, denial, resentment, anger, rage, sadness, and loss. Most people also go through a period of depression, which, unchecked, can lead to even more problems than just coping with vision loss. Ask for help if you need it. Your loved ones, family, friends and even others with AMD are there to help you.
Learning to carry on in new ways is the key. People who learn to adapt so they can continue to do the things they love fare much better. For example, if reading is your passion, you can adapt by using a magnifier or listening to audiobooks which allow for continued independence and confidence.
The Canadian National Institute for the Blind (CNIB) or other low-vision specialists can help you cope with your vision loss. Both specialists and the CNIB can offer various vision enhancement devices and tips, as well as vision rehabilitation counselling, peer support and other services to help make the most of your remaining vision and increase your independence.
Low vision rehabilitation and a solid support network of family, friends, AMD support groups, and organizations like the CNIB can all help you cope with vision loss.
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