Macular degeneration (MD) is a disease of the central retina (called the macula) that affects central vision. It is the leading cause of vision loss among people over age 65. Because it affects only central vision, macular degeneration does not cause total blindness. But it can make most daily activities like driving and reading difficult or impossible.
What causes it?
The exact cause of macular degeneration is still not understood, but it is thought to be associated with artherosclerotic changes in the tiny blood vessels that nourish the macula, compromising the blood flow to this part of the retina.
Age plays a role in the disease. For this reason, it is was originally referred to as age-related macular degeneration (AMD).
Macular degeneration has two forms:
Dry MD is the more common form, affecting approximately 90 percent of those who have macular degeneration. It typically develops slowly and causes mild visual distortion to moderate central vision loss.
Wet MD affects only 10 percent of people with macular degeneration,
but causes more severe vision loss. In wet MD, new blood vessels that
form under the macula leak fluid and can cause a rapid and severe loss
of central vision.
How common is Macular Degeneration?
Macular degeneration is the most common cause of severe vision loss among individuals over age 65. Age is the greatest risk factor. People over 40 have a 4% risk, over 50 have a 9% risk, over 65 have a 23% risk and over 80 have a 31% risk. It accounts for 45% of the legally blind and 70% of the seriously visually impaired people over 70.
Other risk factors include:
- A family history of MD
- High cholesterol
- A poor ability to tan when young
- Excessive exposure to sunlight
- High dietary intake of saturated fat and cholesterol
- Uncontrolled hypertension
- A high body mass index in men
- Race - MD affects Caucasians more frequently than people of other races
- Gender - Women are twice as likely to develop MD
What are the symptoms of Macular Degeneration?
Macular degeneration is painless. Visual symptoms are constant and limited to the central area of a person's visual field.
- Distorted vision
- Blurred vision
- A central darkened spot or empty area
An amsler grid can be used to monitor for any change in relation to MD. Follow this link for a sample amsler grid.
How is Macular Degeneration Assessed?
Assessment in the past has been by monitoring changes at the macula with an ophthalmoscope. Now, digital photography and retinal scans are used to evaluate and monitor macular degeneration. Digital retinal imaging done on a routine basis can be used to diagnose and monitor changes at the macula. Sometimes dye needs to be injected into a vein in the arm before photography to check for leaks at the macula. This is called fluoroscein angiography and is performed by an ophthalmologist.
Optical Coherence Tomography (OCT) is a recent technique for imaging the retina. It is a noninvasive test which records the features of the retina and displays this information as cross-sectional views, or optical slices. For this procedure, the patient is seated at the OCT device. Laser light is used to map the anatomy of the retina, and the resulting computer images are saved for analysis.
An OCT device is used to map the anatomy of the retina.
This is an OCT image of the macula of a normal, healthy eye. The depression in the center is the fovea. The colors in the OCT image represent the different layers of the retina. Note how smooth and even the layers are.
This is an OCT image of the macula in an eye with wet macular degeneration. The affected tissue layers beneath the retina are no longer smooth and flat.
Can Macular Degeneration be treated?
Though there is currently no widely accepted treatment for dry macular degeneration, promising new medications are currently being developed. The AREDS2 study found that taking daily antioxidants deceases the progression of dry MD. These antioxidants are marketed as MDEyes (which is taken once daily and available for purchase at the practice) or alternatively MacuVision Plus (which is taken twice daily).
Wet MD can be treated with regular injections of anti-VEGFs such as lucentis, avastin and eyelea. If you or a family member has MD, ask your optometrist about treatment options that may be available.
Can Macular Degeneration be prevented?
Recent research suggests certain antioxidant vitamins and other nutritional supplements may slow or prevent the development of macular degeneration in some individuals. Vitamins A, C and E; Zinc; Carotenoids and Lutein can be beneficial in maintaining a healthy retina. These substances, however, have not been shown to reverse existing damage to the retina from MD.
Actions you can take to lower your risk of MD include:
- Get plenty of exercise
- Maintain a proper weight
- Eat a healthy diet including fish and green leafy vegetables
- Avoid smoking
- Take a multiple antioxidant vitamin supplement such as MDEyes daily
- Wear sunglasses when outdoors
Low vision aids
People who have lost vision due to MD can often benefit from low
vision aids. These specialised optical devices provide high
magnification and help a person with MD use their remaining central
vision as effectively as possible. See us for a low vision consultation for further
Author: Stuart Macfarlane