Age-related macular degeneration (AMD) is a chronic eye disease that causes the progressive loss of central vision. While it never causes total blindness, since it leaves peripheral vision intact, it can greatly impact quality of life.
What is macular degeneration? AMD is the result of a deterioration of the macula, a small area of the retina located at the back of the eye, near the optic nerve. The retina is the tissue layer that covers the back of the eye and allows us to form images. When this area deteriorates, it can lead to progressive and sometimes significant vision loss.
There are two types of AMD: the dry form and the wet form.
Dry AMD is the most common and it usually progresses slowly and gradually. Many individuals with this type of AMD retain good vision their whole lives. At any time, however, dry AMD can progress to the more severe form of the disease, which is called wet AMD.
While the wet form is less common, it is much more serious. Wet AMD is characterized by growth of abnormal vessels into the subretinal space. It causes rapid distortion and loss of central vision over a period of weeks to months. This form of the disease accounts for 90 percent of all cases of major AMD-related vision loss.
Early AMD detection helps reduce the loss of visual acuity and even improve vision in certain cases. There is currently no way to predict which patients will evolve from the dry form to the wet form of the disease.
Symptoms Dry AMD progresses slowly. Affected individuals may notice the following changes:
- Needing increasingly more light to read or do small work
- Finding it increasingly difficult to adapt to dark environments such as restaurants with dim lighting
- Difficulty recognizing faces
- Increasing central vision blurriness, which is mainly noticeable when reading
- Visual distortions such as lines that appear wavy or twisted, or objects that appear smaller than they actually are
AMD can affect one or both eyes. If only one eye is affected, the individual may notice very little if any change in visual acuity, since the healthy eye compensates for the weaker one.
When to see a doctor A regular eye exam (at least every three years between the ages of 55 and 64, and every two years after that) will help detect the disease early. It is also important to have an eye exam if you notice any change in your central vision or if you have trouble seeing colours and details.
Causes and risk factors The exact cause of AMD is unknown, but the disease develops in older individuals and is most common in persons above the age of 55.
Other than age, the following factors increase the risk of developing AMD:
- A family history of AMD
- Caucasian descent
- Having hypertension or high cholesterol
- Being obese
- Not eating many fruits and vegetables
Treatment There is no cure for AMD. Studies suggest that taking vitamins may slow the progression of dry AMD. This is why some individuals with the disease will be given a prescription for a vitamin and mineral complex that includes vitamins C, E and A, along with zinc and copper. Your doctor may also suggest eating more of the fruits and vegetables that contain these vitamins, and eating more fish, since studies suggest that these foods may contribute to eye health.
When wet AMD develops, however, a treatment is usually recommended to slow the loss of vision. Three treatment options are available: laser photocoagulation, photodynamic therapy, and antiangiogenic (or anti-VEGF) agents. The latter are antibodies that neutralize the key protein responsible for the growth of abnormal blood vessels, and they are injected directly into the eye.
Laser photocoagulation aims to destroy abnormal blood vessels in the eye and thus prevent other lesions from developing. This therapy is not recommended, however, if the abnormal blood vessels developed directly on the center of the eye or if there are too many of them.
Photodynamic therapy is the use of light to activate a drug injected into the eye. The goal is to destroy the abnormal blood vessels in order to slow the progression of the disease.
Living with AMD Living with reduced visual acuity requires some adjustments:
- Make sure your eyeglasses are properly fitted
- Change your computer screen or its settings in order to make it easier to read
- Improve the lighting in your home
- Use a magnifying glass to assist you in performing tasks that require near vision
- Use caution when driving! Make sure to ask your doctor if your visual acuity is sufficient for driving. Be even more careful in trickier situations such as driving at night or in bad weather. Consider alternate modes of transportation such as public transit or traveling with friends or family members.
Prevention A healthy lifestyle is thought to help prevent AMD. Here are some specific suggestions:
- Get a regular eye exam. According to the Canadian Ophthalmological Society, individuals between the ages of 56 and 65 should undergo an eye exam every three years, and those above the age of 65 should do so every two years, or more often if they suffer from an eye disease.
- Control other diseases that can affect the vascular system, such as hypertension or high cholesterol.
- Stop smoking. Smokers appear to be two to three times more likely to suffer from AMD.
- Maintain a healthy body weight.
- Ensure that your diet includes a lot of fruits and vegetables, and eat fish on a regular basis.
If you have any questions on AMD, don't hesitate to speak to a healthcare professional.