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Age-Related Macular Degeneration (AMD)


What is age-related macular degeneration?

Age-related macular degeneration (AMD) is a disease associated with aging, that gradually destroys sharp, central vision. Central vision is needed for seeing objects clearly and for common daily tasks, such as reading and driving.

AMD affects the macula, the part of the eye that allows you to see fine detail. AMD causes no pain.

In some cases, AMD advances so slowly that people notice little change in their vision. In others. the disease progresses faster and may lead to a loss of vision in both eyes. AMD is a leading cause of vision loss in Americans 60 years of age and older.

AMD occurs in two forms: wet and dry.

Where is the macula?

The macula is located in the center of the retina, the light-sensitive tissue at the back of the eye. The retina instantly converts light, or an image, into electrical impulses. The retina then sends these impulses, or nerve signals, to the brain.

eye diagram

What is wet AMD?

wet AMD

Wet AMD occurs when abnormal blood vessels behind the retina start to grow under the macula. These new blood vessels tend to be very fragile and often leak blood and fluid. The blood and fluid raise the macula from its normal place at the back of the eye. Damage to the macula occurs rapidly.

With wet AMD, loss of central vision can occur quickly. Wet AMD is also known as advanced AMD. It does not have stages, like dry AMD.

An early symptom of wet AMD is that straight lines appear wavy. If you notice this condition, or other changes to your vision, contact your eye care professional at once. You will need a comprehensive dilated eye exam.

What is dry AMD?

dry AMD

Dry AMD occurs when the light-sensitive cells in the macula slowly break down, gradually blurring central vision in the affected eye. As dry AMD gets worse, you may see a blurred spot in the center of your vision. Over time, as less of the macula functions, central vision is gradually lost in the affected eye.

The most common symptom of dry AMD is slightly blurred vision. You may have difficulty recognizing faces. You may need more light for reading and other tasks. Dry AMD generally affects both eyes, but vision can be lost in one eye, while the other seems unaffected.

One of the most common early signs of dry AMD is drusen.

What are drusen?

Drusen are yellow hyaline deposits under the retina. They are often found in people over age 60. Your eye care professional can detect drusen during a comprehensive dilated eye exam.

Drusen alone do not usually cause vision loss. In fact, scientists are unclear about the connection between drusen and AMD. They do know that an increase in the size, or number of drusen, raises a person's risk of developing either advanced dry AMD or wet AMD. These changes can cause serious vision loss.

Dry AMD has three stages, all of which may occur in one or both eyes:

Early AMD - People with early AMD have either several small drusen, or a few medium-sized drusen. At this stage, there are no symptoms and no vision loss.

Intermediate AMD - People with intermediate AMD have either many medium-sized drusen, or one or more large drusen. Some people see a blurred spot in the center of their vision. More light may be needed 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 supporting tissue in the central retinal area. This breakdown can cause a blurred spot in the center of your vision. Over time, the blurred spot may get bigger and darker, taking more of your central vision. You may have difficulty reading or recognizing faces, until they are very close to you.

If you have vision loss from dry AMD in one eye only, you may not notice any changes in your overall vision. With the other eye seeing clearly, you can still drive, read and see fine details. You may notice changes in your vision only if AMD affects both eyes. If blurriness occurs in your vision, see an eye care professional for a comprehensive dilated eye exam.

Ninety percent of all people with AMD have this type. Scientists are still not sure what causes dry AMD.

Frequently Asked Questions

Which is the more common - the dry form or the wet form?

The dry form is much more common. More than 85 percent of all people with intermediate and advanced AMD combined, have the dry form.

However, if only advanced AMD is considered, about two-thirds of patients have the wet form. Because almost all vision loss comes from advanced AMD, the wet form leads to significantly more vision loss than the dry form.

Can the dry form turn into the wet form?

Yes. All people who have the wet form, had the dry form first.

The dry form can advance and cause vision loss without turning into the wet form. The dry form also can suddenly turn into the wet form, even during early stage AMD. There is no way to tell if, or when the dry form will turn into the wet form.

The dry form has early and intermediate stages. Does the wet form have similar stages?

No. The wet form is considered advanced AMD.

Can advanced AMD be either the dry form or the wet form?

Yes. Both the wet form and advanced dry form are considered advanced AMD. Vision loss occurs with either form. In most cases, only advanced AMD can cause vision loss.

People who have advanced AMD in one eye, are at especially high risk of developing advanced AMD in the other eye.

Causes and Risk Factors

Who is at risk for AMD?

The greatest risk factor is age. Although AMD may occur during middle age, studies show that people over age 60 are clearly at greater risk than other age groups. For instance, a large study found that people in middle-age have about a 2 percent risk of getting AMD, but this risk increased to nearly 30 percent in those over age 75.

Other risk factors include:

Can my lifestyle make a difference?

Your lifestyle can play a role in reducing your risk of developing AMD.

Symptoms and Detection

What are the symptoms?

Both dry and wet AMD cause no pain.

Dry AMD: The most common early sign is blurred vision. As fewer cells in the macula are able to function, people will see details less clearly in front of them, such as faces or words in a book. Often this blurred vision will go away in brighter light. If the loss of these light-sensing cells becomes great, people may see a small (but growing) blind spot in the middle of their field of vision.

Wet AMD: The classic early symptom is that straight lines appear crooked. This results when fluid from the leaking blood vessels gathers and lifts the macula, distorting vision. A small blind spot may also appear in wet AMD, resulting in loss of one's central vision.

normal visionvision with AMD
Normal vision versus vision of a patient with AMD

How is AMD detected?

Your eye care professional may suspect AMD if you are over 60 and have had recent changes in your central vision. To look for signs of the disease, he or she will use eye drops to dilate (enlarge) your pupils. Dilating the pupils allows your eye care professional to view the back of the eye better.

AMD is detected during a comprehensive eye exam that includes:

Visual Acuity Test - This eye chart measures how well you see at various distances.

dilated exam

Dilated Eye Exam - Drops are placed in your eyes to widen (dilate) the pupils. This allows the eye care professional to see more of the inside of your eyes to check for signs of the disease. Your eye care professional uses a special magnifying lens to examine your retina eye pressureand optic nerve for signs of damage and other eye problems. After the exam, your close-up vision may remain blurred for several hours.


Tonometry - An instrument measures the pressure inside the eye. Numbing drops may be applied to your eye for this test.


Your eye care professional also may do other tests to learn more about the structure and health of your eye.

During an eye exam, you may be asked to 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 may notice that the straight lines in the pattern appear wavy. You may notice that some of the lines are missing. These may be signs of AMD.

Amsler grid normal Amsler grid abnormal

If your eye care professional believes you need treatment for wet AMD, he or she may suggest a fluorescein angiogram. In this test, a special dye is injected into your arm. Pictures are taken as the dye passes through the blood vessels in your retina. The test allows your eye care professional to identify any leaking blood vessels and recommend treatment.

Treatment

How is wet AMD treated?

Wet AMD can be treated with laser surgery, photodynamic therapy, and injections into the eye. None of these treatments is a cure for wet AMD. The disease and loss of vision may progress despite treatment.

Laser Surgery: This procedure uses a laser to destroy the fragile, leaky blood vessels. A high energy beam of light is aimed directly onto the new blood vessels and destroys them, preventing further loss of vision. However, laser treatment may also destroy some surrounding healthy tissue and some vision. Only a small percentage of people with wet AMD can be treated with laser surgery. Laser surgery is more effective if the leaky blood vessels have developed away from the fovea (central part of the macula). Laser surgery is performed in a doctor's office or eye clinic.


The risk of new blood vessels developing after laser treatment is high. Reapeated treatments may be necessary. In some cases, vision loss may progress despite treatments.


Photodynamic Therapy (PDT): A photosensitive drug called Visudyne (verteporfin) is injected into your arm. It travels throughout the body, including the new blood vessels in your eye. The drug tends to "stick" to the surface of new blood vessels. A light is then shined into your eye for about 90 seconds. The light activates the drug. The activated drug destroys the new blood vessels and leads to a slower rate of vision decline. Unlike laser surgery, this drug does not destroy surrounding healthy tissue. Because the drug is activated by light, you must avoid exposing your skin or eyes to direct sunlight, or bright indoor light, for 5 days after treatment.


PDT is relatively painless. It takes about 20 minutes and can be performed in a doctor's office.


PDT slows the rate of vision loss, but it does not stop vision loss or restore vision in eyes already damaged bye advanced AMD. Treatment results often are temporary. You may need to be treated again.


Anti-Angiogenesis Therapy: Wet AMD can now be treated with new drugs that are injected into the eye (anti-VEGF therapy). Abnormally high levels of a specific growth factor (VEGF) occur in eyes with wet AMD and promote the growth of abnormal new blood vessels (angiogenesis). Some of the anti-angiogenic drugs used in this therapy include Avastin (bevicizumab), Lucentis (ranibizumab) and Macugen (pegaptanib). This drug treatment blocks the effect of the growth factor.


You will need multiple injections that may be given as often as monthly. The eye is numbed before each injection. After the injection, you will remain in the doctor's office for a while, and your eye will be monitored. This drug treatment can help slow down vision loss from AMD and in some cases, improve sight.

How is dry AMD treated?

Once dry AMD reaches the advanced stage, no form of treatment can prevent vision loss. However, treatment can delay and possibly prevent intermediate AMD from progressing to the advanced stage, in which vision loss occurs.

AREDS

The National Eye Institute's Age-Related Eye Disease Study (AREDS) found that taking a specific high-dose formulation of antioxidants and zinc, significantly reduces the risk of advanced AMD and its associated vision loss. Slowing AMD's progression from the intermediate stage to the advanced stage will save the vision of many people.

The AREDS formulation is not a cure for AMD. It will not restore vision already lost from the disease. However, it may delay the onset of advanced AMD. It may help people who are at high risk for developing advanced AMD, keep their vision.

There is no need for those diagnosed with early stage AMD to take the AREDS formulation, since the study did not find that AREDS provided a benefit to those with early stage AMD.

Can diet alone provide the same high levels of antioxidants and zinc as the AREDS formulation?

No. The high levels of vitamins and minerals are diffucult to achieve from diet alone. However, previous studies have suggested that people who have diets rich in green leafy vegetables, have a lower risk of developing AMD.

Can a daily multivitamin alone provide the same high levels of antioxidants and zinc as the AREDS formulation?

No. The formulation's levels of antioxidants and zinc are considerably higher than the amounts in any daily multivitamin.

If you are already taking daily multivitamins and your doctor suggests you take the high-dose AREDS formulation, be sure to review all your vitamin supplements with your doctor before you begin.

How can I take care of my vision now that I have AMD?

Dry AMD: If you have dry AMD, you should have a comprehensive dilated eye exam at least once a year. Your eye care professional can monitor your condition and check for other eye diseases. Also, if you have intermediate AMD in one or both eyes, or advance AMD in one eye only, your doctor may suggest that you take the AREDS formulation containing the high levels of antioxidants and zinc.

Because dry AMD can turn into wet AMD at any time, you should get an Amsler grid from your eye care professional. Use the grid every day to evaluate your vision for signs of wet AMD. This quick test works best for people that still have good central vision. Check each eye separately. Cover one eye and look at the grid. Repeat with the other eye. If you detect any changes in the apprearance of this grid, or in your every day vision while reading the newspaper, or watching television, get a comprehensive dilated eye exam.

Wet AMD: If you have wet AMD and your doctor advises treatment, do not wait. After laser surgery or photodynamic therapy, you will need frequent eye exams to detect any recurrence of leaking blood vessels. Studies show that people who smoke have a greater risk of recurrence than those who don't. In addition, check your vision at home with the Amsler grid. If you detect any changes, schedule an eye exam immediately.

What can I do if I have already lost some vision from AMD?

If you have lost some sight from AMD, don't be afraid to use your eyes for reading, watching TV, and other routine activities. Normal use of your eyes will not cause further damage to your vision.

You can ask your eye care professional about low vision services and devices that may help you make the most of your remaining vision.

Current Research

What research is being done?

The National Eye Institute is conducting and supporting a number of studies to learn more about AMD. For example, scientists are:

Studying the possibility of transplanting healthy cells into a diseased retina.

Evaluating families with a history of AMD, to understand genetic and hereditary factors that may cause the disease.

Looking at certain anti-inflammatory treatments for the wet form of AMD.

This research should help provide better ways to detect, treat and prevent vision loss in people with AMD.


Source - National Eye Institute (NEI) of the National Institutes of Health (NIH)

Disclaimer: The information contained in this website does not substitute for the advice of a qualified eye care professional and is not intended to constitute medical advice.