Macular Degeneration Age Related

 

Macular Degeneration Age Related

Definition

Macular degeneration is the leading cause of severe vision loss in people over age 60. It occurs when the small central portion of the retina, known as the macula, deteriorates. The retina is the light-sensing nerve tissue at the back of the eye. Because the disease develops as a person ages, it is often referred to as age-related macular degeneration (AMD). Although macular degeneration is almost never a totally blinding condition, it can be a source of significant visual disability.

There are two main types of age-related macular degeneration:

Dry form. The "dry" form of macular degeneration is characterized by the presence of yellow deposits, called drusen, in the macula. A few small drusen may not cause changes in vision; however, as they grow in size and increase in number, they may lead to a dimming or distortion of vision that people find most noticeable when they read. In more advanced stages of dry macular degeneration, there is also a thinning of the light-sensitive layer of cells in the macula leading to atrophy, or tissue death. In the atrophic form of dry macular degeneration, patients may have blind spots in the center of their vision. In the advanced stages, patients lose central vision.

Wet form. The "wet" form of macular degeneration is characterized by the growth of abnormal blood vessels from the choroid underneath the macula. This is called choroidal neovascularization. These blood vessels leak blood and fluid into the retina, causing distortion of vision that makes straight lines look wavy, as well as blind spots and loss of central vision. These abnormal blood vessels and their bleeding eventually form a scar, leading to permanent loss of central vision.

Most patients with macular degeneration have the dry form of the disease and can lose some form of central vision. However, the dry form of macular degeneration can lead to the wet form. Although only about 10% of people with macular degeneration develop the wet form, they make up the majority of those who experience serious vision loss from the disease. 

Source : WebMD

 

Organ

The eye organ affected by AMD is the macula is the central area of the retina, and is reached differently according to the form of AMD.

 

Symptoms

The main early symptom is blurring of central vision despite using your usual glasses. In the early stages of the condition you may notice that:

You need brighter light to read by.

Words in a book or newspaper may become blurred.

Colours appear less bright.

You have difficulty recognising faces.

One specific early symptom to be aware of is visual distortion. Typically, straight lines appear wavy or crooked. For example, the lines on a piece of graph paper, or the lines between tiles in a bathroom, or the border of any other straight object, etc.

A 'blind spot' then develops in the middle of your visual field. This tends to become larger over time as more and more rods and cones degenerate in the macula.

Visual hallucinations are common in people with severe visual loss of any cause. Visual hallucinations (also called Charles Bonnet syndrome) can occur if you have severe AMD. People see different images, from simple patterns to more detailed pictures. The experience can be upsetting but is less frightening if you are aware that it can happen in AMD. Importantly, it does not mean you are developing a serious mental illness. If you do develop visual hallucinations they typically improve by 18 months but in some people they last for years.

Source : Patient 

 

Frequency

Macular degeneration is the leading cause of vision loss among older Americans, and due to the ageing of the U.S. population, the number of people affected by AMD is expected to increase significantly in the years ahead.

In 2010, approximately 2.07 million Americans had advanced age-related macular degeneration, and that number is expected to grow to 5.44 million in 2050.

AMD is most common among the older white population, affecting more than 14 percent of white Americans age 80 and older. Among Americans age 50 and older, advanced macular degeneration affects 2.1 percent of this group overall, with whites being affected more frequently than blacks, non-white Hispanics and other ethnic groups (2.5 percent vs. 0.9 percent). 

Source : All About Vision

 

Causes

As the name suggests, age-related macular degeneration is more common in older adults. In fact, it is the leading cause of severe vision loss in adults over age 60.

Macular degeneration 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 macular degeneration. Talk to your eye doctor about your individual risk.

Smoking, high blood pressure, high cholesterol, obesity, and being light skinned, female, and having a light eye color are also risk factors for macular degeneration.

Source : WebMD

 

Evolution

People rarely lose all of their vision from age-related macular degeneration. They may have poor central vision, but they are still able to perform many normal daily activities.

The wet form of macular degeneration is a leading cause of irreversible vision loss. When both eyes are affected, you may experience a significant decrease in your quality of life.

The dry form of age-related macular degeneration is much more common and tends to progress more slowly, allowing you to keep most of your vision. 

Source : WebMD

 

Prevention

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.

Source : All About Vision

 

Diagnosis

If you develop symptoms suggestive of AMD, your doctor or optician (optometrist) will refer you to an eye specialist (ophthalmologist). This should be done urgently, especially if there is any suggestion of wet AMD. The ophthalmologist may ask you to look at a special piece of paper with horizontal and vertical lines to check your visual fields. If you find that any section of the lines is missing or distorted, then AMD is a possible cause of the visual problem. The ophthalmologist will examine the back of your eye with a slit lamp microscope. This is a magnifying piece of equipment where the ophthalmologist examines your retinae through what look like binoculars. Digital photographs can be taken of the retinae. The ophthalmologist will look for the typical changes that occur with dry AMD and wet AMD.

Another test called ocular coherence tomography is becoming more commonly used. This is a non-invasive test that uses special light rays to scan the retina. It can give very detailed '3D' information about the macula, and can show if the macula is thickened or abnormal. This test is useful when there is doubt about whether AMD is the wet or dry form. It is also a useful test to assess and monitor the results of any treatment.

If wet AMD is diagnosed or suspected, then a further test called fluorescein angiography may be done. For this test a dye is injected into a vein in your arm. Then, by looking into your eyes with a magnifier and taking pictures with a special camera, the ophthalmologist can see where any dye leaks into the macula from the abnormal leaky blood vessels. This test can give an indication of the extent and severity of the condition. 

Source : Patient

 

Treatment

Early AMD

Currently, no treatment exists for early AMD, which in many people shows no symptoms or loss of vision. Your eye care professional may recommend that you get a comprehensive dilated eye exam at least once a year. The exam will help determine if your condition is advancing.

As for prevention, AMD occurs less often in people who exercise, avoid smoking, and eat nutritious foods including green leafy vegetables and fish. If you already have AMD, adopting some of these habits may help you keep your vision longer.

 

Intermediate and late AMD

Researchers at the National Eye Institute tested whether taking nutritional supplements could protect against AMD in the Age-Related Eye Disease Studies (AREDS and AREDS2). They found that daily intake of certain high-dose vitamins and minerals can slow progression of the disease in people who have intermediate AMD, and those who have late AMD in one eye.

The first AREDS trial showed that a combination of vitamin C, vitamin E, beta-carotene, zinc, and copper can reduce the risk of late AMD by 25 percent. The AREDS2 trial tested whether this formulation could be improved by adding lutein, zeaxanthin or omega-3 fatty acids. Omega-3 fatty acids are nutrients enriched in fish oils. Lutein, zeaxanthin and beta-carotene all belong to the same family of vitamins, and are abundant in green leafy vegetables.

The AREDS2 trial found that adding lutein and zeaxanthin or omega-three fatty acids to the original AREDS formulation (with beta-carotene) had no overall effect on the risk of late AMD. However, the trial also found that replacing beta-carotene with a 5-to-1 mixture of lutein and zeaxanthin may help further reduce the risk of late AMD. Moreover, while beta-carotene has been linked to an increased risk of lung cancer in current and former smokers, lutein and zeaxanthin appear to be safe regardless of smoking status.

 

Here are the clinically effective doses tested in AREDS and AREDS2:

500 milligrams (mg) of vitamin C

400 international units of vitamin E

80 mg zinc as zinc oxide (25 mg in AREDS2)

2 mg copper as cupric oxide

15 mg beta-carotene, OR 10 mg lutein and 2 mg zeaxanthin

A number of manufacturers offer nutritional supplements that were formulated based on these studies. The label may refer to “AREDS” or “AREDS2.”

If you have intermediate or late AMD, you might benefit from taking such supplements. But first, be sure to review and compare the labels. Many of the supplements have different ingredients, or different doses, from those tested in the AREDS trials. Also, consult your doctor or eye care professional about which supplement, if any, is right for you. For example, if you smoke regularly, or used to, your doctor may recommend that you avoid supplements containing beta-carotene.

Even if you take a daily multivitamin, you should consider taking an AREDS supplement if you are at risk for late AMD. The formulations tested in the AREDS trials contain much higher doses of vitamins and minerals than what is found in multivitamins. Tell your doctor or eye care professional about any multivitamins you are taking when you are discussing possible AREDS formulations.

You may see claims that your specific genetic makeup (genotype) can influence how you will respond to AREDS supplements. Some recent studies have claimed that, depending on genotype, some patients will benefit from AREDS supplements and others could be harmed. These claims are based on a portion of data from the AREDS research. NEI investigators have done comprehensive analyses of the complete AREDS data. Their findings to date indicate that AREDS supplements are beneficial for patients of all tested genotypes. Based on the overall data, the American Academy of Ophthalmology (link is external) does not support the use of genetic testing to guide treatment for AMD.

Finally, remember that the AREDS formulation is not a cure. It does not help people with early AMD, and will not restore vision already lost from AMD. But it may delay the onset of late AMD. It also may help slow vision loss in people who already have late AMD.

 

Advanced neovascular AMD

Neovascular AMD typically results in severe vision loss. However, eye care professionals can try different therapies to stop further vision loss. You should remember that the therapies described below are not a cure. The condition may progress even with treatment.

Injections. One option to slow the progression of neovascular AMD is to inject drugs into the eye. With neovascular AMD, abnormally high levels of vascular endothelial growth factor (VEGF) are secreted in your eyes. VEGF is a protein that promotes the growth of new abnormal blood vessels. Anti-VEGF injection therapy blocks this growth. If you get this treatment, you may need multiple monthly injections. Before each injection, your eye will be numbed and cleaned with antiseptics. To further reduce the risk of infection, you may be prescribed antibiotic drops. A few different anti-VEGF drugs are available. They vary in cost and in how often they need to be injected, so you may wish to discuss these issues with your eye care professional.

Photodynamic therapy. This technique involves laser treatment of select areas of the retina. First, a drug called verteporfin will be injected into a vein in your arm. The drug travels through the blood vessels in your body, and is absorbed by new, growing blood vessels. Your eye care professional then shines a laser beam into your eye to activate the drug in the new abnormal blood vessels, while sparing normal ones. Once activated, the drug closes off the new blood vessels, slows their growth, and slows the rate of vision loss. This procedure is less common than anti-VEGF injections, and is often used in combination with them for specific types of neovascular AMD.

Laser surgery. Eye care professionals treat certain cases of neovascular AMD with laser surgery, though this is less common than other treatments. It involves aiming an intense “hot” laser at the abnormal blood vessels in your eyes to destroy them. This laser is not the same one used in photodynamic therapy which may be referred to as a “cold” laser. This treatment is more likely to be used when blood vessel growth is limited to a compact area in your eye, away from the center of the macula, that can be easily targeted with the laser. Even so, laser treatment also may destroy some surrounding healthy tissue. This often results in a small blind spot where the laser has scarred the retina. In some cases, vision immediately after the surgery may be worse than it was before. But the surgery may also help prevent more severe vision loss from occurring years later. 

Source : NEI

 

Images

  Normal vision

Eye disease simulation, normal vision

SourceBy National Eye Institute, National Institutes of Health [Public domain], via Wikimedia Commons

 

The same view with age-related macular degeneration

Eye disease simulation, age-related macular degeneration

SourceBy National Eye Institute, National Institutes of Health [Public domain], via Wikimedia Commons

 

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