Age-Related Macular Degeneration
What is macular degeneration?
Macular degeneration is a condition that affects the macula, the part of the eye that allows a person to see fine detail. It causes problems with central vision, which is the vision used to see objects clearly. People with macular degeneration might have trouble with daily activities that require central vision, such as reading and driving.
Age-related macular degeneration (AMD) and Stargardt’s disease are two types of macular degeneration.
What is age-related macular degeneration (AMD)?
AMD is a type of macular degeneration that happens as the result of aging, and is a leading cause of vision loss in Americans 60 years of age and older.
AMD can happen slowly over time. In some cases, it happens so slowly that the person does not notice a change in vision. In other cases, changes happen more rapidly and lead to drastic vision changes, such as a loss of vision in both eyes.
There are two types of AMD: wet and dry.
What is wet AMD?
Wet AMD happens when abnormal blood vessels behind the retina, the light-sensitive tissue at the back of the eye, start to grow under the macula, the area responsible for central vision. These blood vessels tend to be very fragile and often leak blood and fluid. The blood and fluid damage the macula by disrupting and lifting it from its normal position at the back of the eye. Wet AMD is also known as “advanced” AMD.
People with wet AMD can lose their central vision quickly. An early symptom of wet AMD is that straight lines, such as those on door edges or window blinds, appear wavy. If you have this symptom or other sudden vision changes, such as blind spots in your central vision, contact your eye doctor right away for a comprehensive dilated eye exam.
What is dry AMD?
Dry AMD is the most common type of AMD. It happens when the light-sensitive cells in the macula slowly break down. This gradually blurs central vision in the affected eye. As dry AMD worsens, a blurred spot might appear in the center of vision. Over time, dry AMD will damage more of the cells in the macula, leading to a loss of vision in the affected eye. Dry AMD generally affects both eyes, but vision can be lost in one eye while the other eye remains unaffected.
Often, an early physical sign of dry AMD is the presence of drusen. Drusen are yellow deposits under the retina, and can be found readily in people over age 60. Your eye doctor can detect drusen during a comprehensive dilated eye exam. Drusen alone do not usually cause vision loss, but an increase in the size or number of drusen might be a sign that a person will develop either severe dry AMD or wet AMD.
Dry AMD has three stages, and each can occur in one or both eyes.
The stages are:
- Early dry AMD – People with early dry AMD have either several small drusen or a few medium-sized drusen. At this stage, there are often no symptoms or vision loss.
- Intermediate dry AMD – People with intermediate AMD have either many medium-sized drusen or one or more large drusen. Some people with this stage see a blurred spot in the center of their vision. They might also require more light for reading and other tasks.
- Advanced dry AMD – In addition to drusen, people with advanced dry AMD have a breakdown of light-sensitive cells and associated tissue in the central area of the retina. This breakdown can cause a blurred spot in the center of vision. Over time, the blurred spot can enlarge and darken, taking up more of the central vision. A person with this stage might have difficulty reading or recognizing faces until they are very close.People who have advanced AMD in one eye are at especially high risk of developing advanced AMD in the other eye.
Dry AMD can also turn into wet AMD. This can happen suddenly, even during early stage AMD. There is no way to know ahead of time if or when the dry form will turn into the wet form. In addition, the dry form can advance and cause vision loss without ever turning into the wet form. All people who have the wet form had the dry form first.
Who is at risk for AMD?
The greatest risk factor for AMD is age. Although AMD can affect middle-aged people, people over 60 are at a greater risk than other age groups.
Other risk factors include:
- Obesity – Research studies suggest a link between obesity and the progression of early and intermediate stages AMD to advanced AMD.
- Race – Whites are much more likely to lose vision from AMD than African Americans.
- Family history – People who have immediate family members with AMD are at a higher risk of developing the disease.
- Gender – Women appear to be at greater risk of AMD than men.
Can my lifestyle make a difference?
Yes. To reduce your chances of developing AMD, you can:
- Eat a healthy diet high in green leafy vegetables and fish
- Quit smoking, if you smoke
- Control your blood pressure
- Maintain a healthy weight
What are the symptoms of AMD?
Symptoms depend on the type of AMD. Both dry and wet AMD cause no pain.
In dry AMD, the most common early sign is blurred vision. As fewer cells in the macula are able to function, the person will see some details, such as facial features or words in a book, less clearly. Often this blurred vision will go away in brighter light. If there is significant loss of macular cells, the person might see a small blind spot in the middle of his or her field of vision that grows larger over time.
If you have vision loss from dry AMD in one eye only, you might not notice any changes in your overall vision. While your other eye sees clearly, you might still be able to drive, read, and see fine details normally. You might not notice changes in your vision until the AMD affects both eyes.
If you start to have blurriness in your vision, see an eye doctor for a comprehensive dilated eye exam.
For wet AMD, the most common early symptom is that straight lines appear crooked or wavy. A small blind spot might also appear in wet AMD, causing a loss of central vision.
How is AMD detected?
AMD is detected during a comprehensive eye exam. This exam might include:
- Visual acuity test – This test uses an eye chart to measure how well you see at various distances.
- Dilated eye exam – For this test, the eye doctor will put drops in your eyes to widen, or dilate, the pupils. He or she will then use a special magnifying lens to examine your retina and optic nerve for signs of AMD and other eye problems. After the exam, your close-up vision might remain blurred for several hours.
- Tonometry – This test involves an instrument that measures the pressure inside the eye. Your doctor might apply numbing drops to your eye for this test.
- Amsler grid – During an eye exam, your doctor might have you look at an Amsler grid. The pattern of the grid resembles a checkerboard. You will cover one eye and stare at a black dot in the center of the grid. While staring at the dot, you might notice that the straight lines in the pattern appear wavy, or that that some of the lines are missing. These can be signs of AMD.
Your eye doctor might also do other tests to learn more about the structure and health of your eye.
How is AMD treated?
There is no cure for AMD, but there are treatments that can keep the condition from getting worse. Treatments depend on the type of AMD:
Dry AMD – Currently, there are no available treatments that can reverse the effects dry AMD. Your eye doctor might recommend taking high doses of zinc, beta carotene, and vitamins C and E to keep your dry AMD from getting worse. Scientists are also looking into treatments that might delay vision loss from dry AMD.
Wet AMD – Similar to dry AMD, treatments usually cannot reverse the effects of wet AMD. But they can prevent further damage. Treatments for wet AMD include:
- Injections – Wet AMD can be treated with medications that are injected into the eye (called “anti-VEGF therapy”). Eyes with wet AMD have high levels of a certain kind of growth factor that promotes the growth of abnormal new blood vessels. This drug treatment blocks the effects of the growth factor. It can help slow down vision loss from AMD and, in some cases, improve vision.People who get this treatment will need many injections. The injections will be given as often as monthly. The eye is numbed before each injection. After the injection, the person remains in the doctor’s office for a while so the eye can be monitored.
- Medication – Three medications, ranibizumab, aflibercept and pegaptanib have been approved by the FDA to preserve vision by slowing or blocking the growth of new blood vessels. If your doctor prescribes one of these medications, he or she will inject it into your eye once your eye has been cleaned and numbed. If you take ranibizumab, you will have injections once a month. If you take aflibercept or pegaptinib, you will have injections less often.Another drug, bevacizumab, was originally approved to treat colorectal cancer, but also reduces leakage from abnormal blood vessels in the retina. Many other drugs are also being studied.
- Photodynamic therapy – This treatment involves a cold laser combined with a light-sensitizing medication called verteporfin. It can help close new abnormal blood vessels without creating a scar. This can help with some types of wet AMD.
- Photocoagulation – This treatment involves using a high-energy laser beam to destroy the new abnormal blood vessels. This can help with some types of wet AMD.
- Surgery – This can help with some types of wet AMD.
If you need treatment for wet AMD, your doctor might suggest a test called a fluorescein angiogram. In this test, a special dye is injected into the arm. Pictures are taken as the dye passes through the blood vessels in the retina. This test allows the eye doctor to identify any leaking blood vessels and recommend treatment.
How can I take care of my vision now that I have AMD?
If you have dry AMD, your eye doctor might give you an Amsler grid to test your vision for signs of wet AMD. To use your Amsler grid, check each eye by looking at the grid with the other eye covered. If you detect any changes in the appearance of this grid or in your general vision, call your eye doctor.
If you have wet AMD, do not wait to get any of the treatments your doctor recommends. After you get treated, you should have frequent eye exams to check for any leaking blood vessels. In addition, check your vision at home with the Amsler grid. If you detect any changes, call your eye doctor.