What Is Age-Related Macular Degeneration?


Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a disease that causes the gradual loss of sight due to blurring or loss of central vision. This is often as a result of a deterioration of the macula, a yellow pigmented structure at the back of the eye that is responsible for our detailed colour vision.

The severity of the disease depends on each person and on how quickly it is detected. AMD is a chronic disease – it cannot be cured and in many patients sight cannot be restored after it is lost. However certain forms of the disease can be treated. Early detection is important to potentially stop the spread of the disease and to protect your sight.

Research by the Macular Pigment Research Group in Waterford Institute of Technology estimates that seven per cent of Irish people aged 50 years or older are living with AMD. Therefore, AMD is the leading cause of sight loss in this age group, with the number of people affected due to increase in the coming years due to our aging population.

There are two forms of AMD, Early and Late. In Early AMD the signs that the retina is being damaged are only visible to your eye care practitioner (optometrist or eye doctor). At this stage the damage does not affect sight and people are unaware of the condition. This highlights the importance of regular eye examinations to detect AMD in its early stages.

Some people progress from Early to Late AMD, where the condition causes loss of vision. There are two forms of Late AMD, Dry and Wet AMD. The wet form is more severe and vision degenerates more rapidly, however this form is less common. Abnormal blood vessels grow under the macula which bleed and leak fluid, this causes central vision to become damaged or distorted. This is called choroidal neovascularization (CNV).

What Is Age-Related Macular Degeneration?

The dry form is more common (around 85% of people with AMD have the dry form) but it is less severe and vision degenerates over a longer period of time. Dry AMD is caused when deposits, called ‘drusen’, form at the macula. Only your eye care professional can tell you which form you may have.

Although sight loss caused by AMD can cause difficulty doing everyday tasks like driving, reading and watching TV, AMD rarely causes total blindness.

Which part of the eye is affected?

AMD affects the macular region of the retina which is used for straight ahead sight. Activities which rely on the macula functioning well are reading, writing, looking at detailed objects, and colour vision.

What are the types of AMD?

AMD is described as either dry or wet. Dry AMD is the most common and results in a gradual loss of central vision. Wet AMD is rarer and leads to sudden and significant changes in vision.

What are the stages of AMD?

There are three stages of AMD defined in part by the size and number of drusen under the retina. It is possible to have AMD in one eye only, or to have one eye with a later stage of AMD than the other.

Early AMD. Early AMD is diagnosed by the presence of medium-sized drusen, which are about the width of an average human hair. People with early AMD typically do not have vision loss.

Intermediate AMD. People with intermediate AMD typically have large drusen, pigment changes in the retina, or both. Again, these changes can only be detected during an eye exam. Intermediate AMD may cause some vision loss, but most people will not experience any symptoms.

Late AMD. In addition to drusen, people with late AMD have vision loss from damage to the macula. There are two types of late AMD:

In geographic atrophy (also called dry AMD), there is a gradual breakdown of the light-sensitive cells in the macula that convey visual information to the brain, and of the supporting tissue beneath the macula. These changes cause vision loss.

In neovascular AMD (also called wet AMD), abnormal blood vessels grow underneath the retina. (“Neovascular” literally means “new vessels.”) These vessels can leak fluid and blood, which may lead to swelling and damage of the macula. The damage may be rapid and severe, unlike the more gradual course of geographic atrophy. It is possible to have both geographic atrophy and neovascular AMD in the same eye, and either condition can appear first.

AMD has few symptoms in the early stages, so it is important to have your eyes examined regularly. If you are at risk for AMD because of age, family history, lifestyle, or some combination of these factors, you should not wait to experience changes in vision before getting checked for AMD.

Not everyone with early AMD will develop late AMD. For people who have early AMD in one eye and no signs of AMD in the other eye, about five percent will develop advanced AMD after 10 years. For people who have early AMD in both eyes, about 14 percent will develop late AMD in at least one eye after 10 years. With prompt detection of AMD, there are steps you can take to further reduce your risk of vision loss from late AMD.

If you have late AMD in one eye only, you may not notice any changes in your overall vision. With the other eye seeing clearly, you may still be able to drive, read, and see fine details. However, having late AMD in one eye means you are at increased risk for late AMD in your other eye. If you notice distortion or blurred vision, even if it doesn’t have much effect on your daily life, consult an eye care professional.

Wet And Dry Forms Of Macular Degeneration

Macular degeneration is diagnosed as either dry (non-neovascular) or wet (neovascular). Neovascular refers to growth of new blood vessels in an area, such as the macula, where they are not supposed to be.

The dry form is more common than the wet form, with about 85 to 90 percent of AMD patients diagnosed with dry AMD. The wet form of the disease usually leads to more serious vision loss.

Dry macular degeneration (non-neovascular). Dry AMD is an early stage of the disease and may result from the aging and thinning of macular tissues, depositing of pigment in the macula or a combination of the two processes.

Dry macular degeneration is diagnosed when yellowish spots known as drusen begin to accumulate in and around the macula. It is believed these spots are deposits or debris from deteriorating tissue.

Gradual central vision loss may occur with dry macular degeneration but usually is not nearly as severe as wet AMD symptoms. However, dry AMD through a period of years slowly can progress to late-stage geographic atrophy (GA) — gradual degradation of retinal cells that also can cause severe vision loss.

No FDA-approved treatments are available for dry macular degeneration, although a few now are in clinical trials.

Two large, five-year clinical trials — the Age-Related Eye Disease Study (AREDS; 2001) and a follow-up study called AREDS2 (2013) — have shown nutritional supplements containing antioxidant vitamins and multivitamins that also contain lutein and zeaxanthin can reduce the risk of dry AMD progressing to sight-threatening wet AMD.

But neither the AREDS nor the AREDS2 study demonstrated any preventive benefit of nutritional supplements against the development of dry AMD in healthy eyes.

Currently, it appears the best way to protect your eyes from developing early (dry) macular degeneration is to eat a healthy diet, exercise and wear sunglasses that protect your eyes from the sun’s harmful UV rays and high-energy visible (HEV) radiation.

Wet macular degeneration (neovascular). In about 10 percent of cases, dry AMD progresses to the more advanced and damaging form of the eye disease. With wet macular degeneration, new blood vessels grow beneath the retina and leak blood and fluid. This leakage causes permanent damage to light-sensitive retinal cells, which die off and create blind spots in central vision.

Choroidal neovascularization (CNV), the underlying process causing wet AMD and abnormal blood vessel growth, is the body’s misguided way of attempting to create a new network of blood vessels to supply more nutrients and oxygen to the eye’s retina. Instead, the process creates scarring, leading to sometimes severe central vision loss.

Wet macular degeneration falls into two categories:

Occult. New blood vessel growth beneath the retina is not as pronounced, and leakage is less evident in the occult CNV form of wet macular degeneration, which typically produces less severe vision loss.

Classic. When blood vessel growth and scarring have very clear, delineated outlines observed beneath the retina, this type of wet AMD is known as classic CNV, usually producing more severe vision loss.

Age-Related Macular Degeneration Symptoms And Signs

Age-related macular degeneration usually produces a slow, painless loss of vision. In rare cases, however, vision loss can be sudden. Early signs of vision loss from AMD include shadowy areas in your central vision or unusually fuzzy or distorted vision.

Viewing a chart of black lines arranged in a graph pattern (Amsler grid) is one way to tell if you are having these vision problems. See how an Amsler grid works by taking a macular degeneration test.

Eye care practitioners often detect early signs of macular degeneration before symptoms occur. Usually this is accomplished through a retinal exam. When macular degeneration is suspected, a brief test using an Amsler grid that measures your central vision may be performed.

If your eye doctor detects some defect in your central vision, such as distortion or blurriness, he or she may order a fluorescein angiography to examine the retinal blood vessels surrounding the macula.

When to seek medical advice

Visit your GP or optometrist if your vision is getting gradually worse. If your vision suddenly gets worse, images are distorted or you notice blind spots in your field of vision, seek medical advice immediately and book an emergency appointment with an optometrist.

If AMD is suspected, you’ll be referred to an ophthalmologist (eye specialist) for tests and any necessary treatment.

Check Your Vision

One easy at-home test for AMD is the Amsler Grid. You can download a copy of the amsler grid here.

How to test with the Amsler Grid

  • Hold the grid at reading distance, about 12 inches (30cm) away from your face.
  • If you wear reading glasses, leave them on. Do not take the test while wearing varifocal or distance glasses.
  • Cover one eye and focus on the centre dot.
  • Make sure you can see all four corners of the grid.
  • If the lines appear missing or wavy, you may have AMD. Contact your doctor immediately.
  • Remember, even if the grid looks normal, you should still attend regular eye exams for early detection of AMD.

What is the cause of AMD?

The exact cause of AMD is unknown, but over the past 20 years, many risk factors for AMD have been discovered. Researchers know that certain genes cause AMD, but they don’t know what triggers the gene. While AMD can be inherited, many lifestyle choices can make progression of the disease worse.

You may be at risk of developing AMD if you are over the age of 50, have a family history of AMD, smoke and if you are overweight or have a poor diet. Other factors include having fair skin and light eyes and having a history of cataracts. Studies have shown that women are more likely to develop AMD.

There are simple steps you can take today to help save your sight. These include eating a balanced vegetable rich diet, exercising regularly and quitting smoking. Many of these are part of living a healthy lifestyle, so your heart and lungs will thank you too.

What treatments are available?

If your optometrist detects something wrong with your eye or suspects you have AMD, he or she will refer you to an ophthalmologist. This person will be able to medically treat your eyes and talk to you about the best course of action for your particular condition. Your eye care practitioner will suggest lifestyle changes that will help slow the progression of AMD, such as stopping smoking and eating a healthy diet. Vitamin supplements may also be recommended.

If Wet AMD is suspected, you may have a test called Fluoroscein Angiography. A special dye is injected into your arm and carried through your bloodstream. As it passes through the blood vessels in your eye, doctors can detect the severity of the leaking and bleeding. If you have Wet AMD, a treatment of anti-VEGF therapy may be recommended to treat the damaged blood vessels in your eye. The success of this therapy depends on early detection and treatment before irreversible scarring and damage occurs.

Internationally, researchers are trying to understand why some people get AMD and others do not. While we understand some of the risk factors and lifestyle choices that may lead to the disease, researchers are also investigating the role of the immune system in the disease progression.

Researchers are also designing ways to deliver medication to the eye that are less invasive methods than current methods. Another key area of research is looking at ways of preventing the early stages of macular degeneration, when natural cell waste materials build up in the retina.

This leads to toxic chemicals forming, which cause retinal cells to die. Drugs are being trialled to see if they can slow the build-up of the toxins. Neuroprotective drugs are also being investigated to see if they can protect the cells of the retina.

For people living with AMD, general eye check-ups are extremely important, because these individuals are still at risk for other kinds of eye problems that can affect the general population and may be treatable. Regular visits to your eye doctor can also make you aware of current advances as we learn more about treating these prevalent diseases.

Who’s affected?

AMD currently affects more than 600,000 people in the UK and is the leading cause of vision loss. By 2020, it’s predicted almost 700,000 people will have late-stage AMD in the UK.

For reasons that are unclear, AMD tends to be more common in women than men. It’s also more common in white and Chinese people.

The condition is most common in people over the age of 50. It’s estimated 1 in every 10 people over 65 have some degree of AMD.

Reducing your risk

It’s not always possible to prevent macular degeneration because it’s not clear exactly what triggers the processes that cause the condition.

Your risk of developing AMD is closely linked to your age and whether you have a family history of the condition.

However, you may be able to reduce your risk of developing AMD, or help prevent it getting worse, by:

  • stopping smoking if you smoke
  • eating a healthy, balanced diet that includes plenty of fruit and vegetables
  • moderating your consumption of alcohol – read more about alcohol units and recommendations
  • trying to achieve or maintain a healthy weight
  • wearing UV-absorbing glasses when outside for long periods
  • Juvenile macular degeneration

In rare cases, macular degeneration can affect younger people. This is sometimes known as juvenile macular degeneration.

It can be present at birth or develop later, but it’s almost always caused by an inherited genetic disorder, such as:

Stargardt’s disease – the most common cause of juvenile macular degeneration, this can start in childhood or early adulthood

Best’s disease – also known as Best’s vitelliform macular dystrophy

Sorsby’s dystrophy – this often begins between the ages of 30 and 40

Who Gets Age-Related Macular Degeneration?

Besides affecting older populations, AMD occurs in whites and females in particular. The disease also can result as a side effect of some drugs, and it seems to run in families.

New evidence strongly suggests smoking is high on the list of risk factors for macular degeneration. Other risk factors for macular degeneration include having a family member with AMD, high blood pressure, lighter eye color and obesity.

Some researchers believe that over-exposure to sunlight also may be a contributing factor in development of macular degeneration, but this theory has not been proven conclusively. High levels of dietary fat also may be a risk factor for developing AMD.

Commonly named risk factors for developing macular degeneration include:

Aging. The prevalence of AMD increases with age. In the United States, approximately one in 14 people over the age of 40 has some degree of macular degeneration. For those over 60, the rate is one in eight (12.5 percent); and for seniors over age 80, one in three (33 percent) has AMD.

Obesity and inactivity. Overweight patients with macular degeneration had more than double the risk of developing advanced forms of macular degeneration compared with people of normal body weight, according to one study reported in Archives of Ophthalmology (June 2003). In the same study, those who performed vigorous activity at least three times weekly reduced their risk of developing advanced AMD, compared with inactive patients.

Heredity. As stated above, recent studies have found that specific variants of different genes are present in most people who have macular degeneration. Studies of fraternal and identical twins may also demonstrate that heredity is a factor in who develops AMD and how severe it becomes.

High blood pressure (hypertension). Investigative Ophthalmology and Vision Science reported the results of a European study demonstrating that high blood pressure may be associated with development of macular degeneration (September 2003).

Smoking. Smoking is a major AMD risk factor and was found in one British study to be directly associated with about 25 percent of AMD cases causing severe vision loss. The British Journal of Ophthalmology in early 2006 also reported study findings showing that people living with a smoker double their risk of developing AMD.

Lighter eye color. Because macular degeneration long has been thought to occur more often among Caucasian populations, particularly in people with light skin color and eye color, some researchers theorized that the extra pigment found in darker eyes was a protective factor against development of the eye disease during sun exposure. But no conclusive evidence as yet has linked excessive sun exposure to development of AMD.

A small study reported in the British Journal of Ophthalmology (January 2006) found no connection between the eye disease and sun exposure. In fact, the same study found no relation at all between lighter eye color, hair color and AMD. That finding is contradicted by several earlier studies indicating that lighter skin and eyes are associated with a greater prevalence of AMD.

Drug side effects. Some cases of macular degeneration can be induced from side effects of toxic drugs such as Aralen (chloroquine, an anti-malarial drug) or phenothiazine. Phenothiazine is a class of anti-psychotic drugs, including brand names of Thorazine (chlorpromazine, which also is used to treat nausea, vomiting and persistent hiccups), Mellaril (thioridazine), Prolixin (fluphenazine), Trilafon (perphenazine) and Stelazine (trifluoperazine).

The American Academy of Ophthalmology notes that findings regarding AMD and risk factors have been contradictory, depending on the study. The only risk factors consistently found in studies to be associated with the eye disease are aging and smoking.

Nutrition And Macular Degeneration

Many organizations and independent researchers are conducting studies to determine if dietary modifications can reduce a person’s risk of macular degeneration and vision loss associated with the condition. And some of these studies are revealing positive associations between good nutrition and reduced risk of AMD.

For example, some studies have suggested a diet that includes plenty of salmon and other coldwater fish, which contain high amounts of omega-3 fatty acids, may help prevent AMD or reduce the risk of its progression.

Other studies have shown that supplements containing lutein and zeaxanthin increase the density of pigments in the macula that are associated with protecting the eyes from AMD.

Visit and bookmark our Eye Nutrition News page for the latest developments in nutritional research that may prevent or limit vision problems from AMD, cataracts and other eye conditions.

For more information visit us our website: https://www.healthinfi.com

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