What is macular degeneration?
The front of the eye contains a lens that focuses images on the retina in the back of the eye. The retina contains special nerve cells that react to light.
These nerve cells are very close together in the middle of the retina, where the eye focuses the images that we see. This part of the retina is called the macula. The macula provides the sharp, straight-ahead vision that allows you to see small detail, read fine print, recognize faces, and see street signs.
Macular degeneration is an eye disease and is the most common type of macular damage in adults. Because the disease develops as a person ages, it is often called age-related macular degeneration (AMD). AMD is the leading cause of vision loss in people over the age of 50 in the United States.
What are the symptoms of age-related macular degeneration?
AMD often does not have symptoms and is not recognized until it affects visual acuity. The first symptom of AMD is usually noticed when straight lines appear wavy. This may lead to a gradual loss of central vision.
Other symptoms of AMD include the following:
- blurriness and dimming of vision
- a dark or blank spot in the center of the vision
- the size or color of something looks different when viewed through different eyes.
If you have any of these symptoms, see an ophthalmologist (eye doctor) as soon as possible.
What causes age-related macular degeneration?
The exact causes of macular degeneration are not known. Risk factors may include:
- genetic factors
- nutritional factors
- high blood pressure
- exposure to direct sunlight over a period of years
- certain medical conditions
What are the types of age-related macular degeneration?
There are two types of AMD – the dry (atrophic) form and the wet (exudative or neovascular) form.
The dry form of AMD affects about 85-90 percent of AMD patients and usually begins when tiny yellow deposits called drusen appear in the macula. Drusen usually do not cause serious loss of vision, but can distort vision. However, for reasons that are not yet understood, sometimes drusen are associated with macular atrophy (thinning) and tissue breakdown, slowly leading to vision loss. Patients may have blind spots in their vision; in the advanced stages, patients may even lose central vision.
The wet form of AMD occurs in about 10-15 percent of AMD patients. It is caused by the growth of abnormal blood vessels beneath the macula that can leak fluid and blood into the eye. The wet form of AMD usually causes major vision problems, such as blind spots and loss of central vision, in the affected eye, and can advance rapidly. These abnormal blood vessels eventually scar, leading to permanent retinal damage and loss of central vision.
Most patients with AMD have the dry form of the disease and will not lose central vision. However, the dry form of AMD can lead to the wet form. People who have the wet form of AMD are much more likely to have serious vision loss. For these patients, early diagnosis and treatment are important to save as much vision as possible.
Because the dry form can change into the wet form, it is very important for people with AMD to monitor their eyesight carefully and see their eye doctor on a regular basis.
AMD may be hereditary, meaning it can be passed on from parents to children. If someone in your family has or had the condition, you may be at higher risk for developing the disease. Talk to your eye doctor about your individual risk.
How is age-related macular degeneration diagnosed?
Your ophthalmologist will perform a complete examination to diagnose AMD. One of the most common early signs of AMD is the presence of drusen. Your doctor can see these during a routine eye exam. Sometimes, early AMD can even be detected using a traditional eye chart exam.
Often, an optical coherence tomography (OCT) picture will be taken. OCT shows how thick the retina is and can identify leaking fluid from abnormal blood vessels.
The doctor may order a fluorescein or indocyanine green angiogram to look for the abnormal blood vessels within or under the retina. During each of these procedures, dye is injected in the arm, and photographs (not X-rays) are taken from a special camera to track the movement of the dye as it reaches the eye, and to show any changes in the retina. If there are new vessels leaking fluid or blood in the macula, the photographs will show their location and their type.
People with macular degeneration can check their own vision with a simple test called the Amsler grid. The Amsler grid is a pattern of straight lines that make perfect squares. The patient looks at a large dot in the middle of the grid and notices any areas where the lines look blurry, wavy, or broken. If the grid lines seem to be more distorted than before, it might be a sign that the macular degeneration is getting worse and needs evaluation.
Early detection of AMD is very important because there are treatments that can delay or reduce the severity of the disease.
How is age-related macular degeneration treated?
Although there is no treatment to reverse the dry form of AMD, eyesight may be helped with low-vision aids, e.g., devices that have special lenses or electronic systems that produce enlarged images of nearby objects. They help people with partial vision make the most of their remaining vision.
The Age-related Eye Disease study (AREDS) found that taking vitamin and mineral supplements can reduce some patients’ chances of developing AMD or reduce the chance of progression. For instance, Vitamins C, E, Lutein, zinc, and copper have been shown to decrease the risk of vision loss in patients with intermediate to advanced dry AMD. Ask your eye doctor if this type of therapy is right for you.
Several options are available to treat the wet form of AMD, but not all are appropriate or successful for all patients. These treatments include:
- Anti-angiogenesis medications — there are several drugs that prevent the growth of abnormal blood vessels. These drugs are injected into the eye at 4-8 week intervals to cause the blood vessels to shrink. This treatment may improve vision in some patients and stabilize it in most patients.
- Photodynamic therapy —The doctor injects a light-sensitive drug into the bloodstream to be absorbed by the abnormal blood vessels in the eye. The doctor then shines a cold laser into the eye to activate the drug, damaging the abnormal blood vessels.
- Laser therapy: High-energy lights are used to destroy actively growing abnormal blood vessels.
What can I expect after drug injection treatment?
After treatment, your physician may order another OCT picture, or sometimes an angiogram, to make sure there are no other areas of blood leakage. If the OCT shows that there is still leakage, more treatment is usually recommended.
Are there any side effects of the anti-angiogenesis eye injections?
Rare complications may include:
- damage to structures in the eye, including more rapid clouding of the lens (cataract)
- in very rare instances, retinal detachment or severe loss of vision may occur. In studies, 1 to 2% of patients receiving the drugs had a heart attack or stroke over the next year, which appears to be a similar rate to that seen in the control group of patients.
Can treatment help if I am legally blind?
Depending upon the cause of legal blindness, it is possible that treatment may help. If recent bleeding or leakage under the retina has resulted in legal blindness, surgery is a possibility. Retinal cell transplants and stem cell therapy are under study; a new implanted electronic retinal “chip” was recently approved for human use and may be an option in highly selected cases.
Can I have treatment if lasers were used as an earlier treatment?
Because bleeding or leakage may occur beneath the retina even after the laser treatment, it is possible that treatment with injected drugs can help.
I have other medical conditions. Can I still have treatment?
Other medical conditions or age should not be a factor if you are considered an appropriate candidate for treatment, although sometimes anti-VEGF injections may be delayed after a recent heart attack or stroke.
What is the outlook for people with AMD?
Unfortunately, AMD can return even after successful treatment. The various treatments can slow the rate of vision loss and hopefully preserve some sight.