What Is AMD? What Is Macular Degeneration?

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Main Category: Eye Health / Blindness
Article Date: 01 Jun 2009 - 9:00 PST

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People with macular degeneration gradually lose their central vision - they find it harder to see things that are directly in front of them - making it much harder to read, write, recognize faces and drive. The macula, or macula lutea (Latin: macula = spot + lutea = yellow) is an oval shaped yellow spot near the center of the retina of the eye. Macular degeneration mainly affects elderly people. It is caused by damage to the retina.

Macular degeneration is a major cause of partial-blindness among people aged 50 plus. Although the person's central vision is affected, there is usually enough peripheral vision to allow other activities of daily life.

Some scientists found that when neurons stop getting visual input from one part of the retina, they begin responding to input from another part of the retina.

Macular degeneration occurs in dry and wet forms

• Dry macular degeneration - this type develops gradually. There is no treatment. There are things the patient can learn to cope with it.


• Wet macular degeneration - this type can develop more quickly. As soon as symptoms appear the patient requires treatment immediately. Wet macular degeneration is more serious than dry macular degeneration.

Who gets macular degeneration?

Generally people over 50 years of age - this is known as age-related AMD (age-related macular degeneration). According to the NHS (National Health Service, UK), AMD affects:

• 2% of people aged 50+
• 8% of people aged 65+
• 20% of people aged 85+

People who have a close relative with AMD have a significantly higher risk (50%) of eventually developing it compared to other people (12%). Scientists believe a new genetic association will better help predict those at risk and ultimately lead to better treatments.

Marilyn Gozdon can tell you from personal experience why it's crucial to know your risks for age-related macular degeneration (AMD).

Younger people can develop macular degeneration. However, this is very rare and is generally caused by a genetic condition. Juvenile Macular Degeneration is also known as Stargardt's disease (STGD).

Below are some more factors which may contribute to the risk:

• High blood pressure (hypertension) - people who suffer from hypertension are more at risk of developing macular degeneration.


• High cholesterol and/or obesity - a higher percentage of obese people and/or people with high blood cholesterol levels are more likely to develop macular degeneration.


• Dietary fat - studies indicate that people who consume a lot of saturated fats have a higher risk of developing macular degeneration.


• Race - studies in the USA indicate that a higher percentage of Caucasian-Americans get macular degeneration compared to African-Americans.


• Light exposure - some studies indicate that high-energy visible light may be a contributory factor. However, other studies do not. A study found that some types of AMD have been linked to low plasma levels of antioxidants and blue light exposure from the sun.


• Smoking - A regular smoker increases his/her chances of developing macular degeneration significantly - in fact, people who currently smoke have four times the risk of developing AMD, compared to lifelong non-smokers.

What are the symptoms of macular degeneration?

The symptoms can be so gradual and subtle that many people do not know they have it for quite a long time. The main symptom is blurring of the person's central vision. Peripheral vision (outer vision) is not affected. The blurred central vision is still there, even when the person wears glasses.

Dry age-related macular degeneration (Dry AMD) symptoms:

• The patient may not notice anything unusual for up to ten years after onset


• If just one eye is affected, it may take even longer before somebody knows he/she has it


• People with dry AMD tend to need a brighter light when reading


• Written or printed texts seem blurry


• Slow recovery of visual function after exposure to bright light


• Colors do not appear as vibrant as they used to


• It becomes more difficult to instantly recognize people's faces


• The sufferer's vision is less defined, hazier

Wet age-related macular degeneration (Wet AMD) symptoms:

The patient may experience all the symptoms mentioned above, plus:

• Symptoms appear faster


• Metamorphopsia - straight lines may seem crooked or wavy


• Central vision blind spot (central scotoma) - the middle of the person's visual field is a total blind spot. If left untreated, this blind spot will get bigger

Diagnosis of macular degeneration

The first point of call for a person who suspects macular degeneration, or something wrong with his/her vision, would be a GP (general practitioner, primary care physician), or an optometrist. If the GP or optometrist believes macular degeneration is a possibility, the patient will be referred to an eye doctor (ophthalmologist).

The ophthalmologist will examine the patient's eyes, especially the back of the eyes, where the retina and macula are. Then there will be a series of tests:

• Amsler grid - the patient will be asked to look at a special grid, which consists of vertical and horizontal lines. Most people with macular degeneration will find that some of the lines on the grid seem distorted, broken, or faded. Depending on what the patient says, the specialist will have a better idea of the degree of macula damage. Most people with detectable macular degeneration symptoms find the lines nearest the center of the grid are the ones that seem distorted, faded, or broken.


• Fluorescein angiography - this test confirms what type of AMD the patient has. It is usually carried out if the specialist suspects wet AMD. A special dye is injected into the patient's arm. Then, he/she will look into the patient's eyes with a special magnifying device, and take a series of pictures of the eye. The pictures will indicate whether the blood vessels behind the macula are leaking. Wet AMD is caused by leaking from the blood vessels behind the macula.


• Coherence tomography - special light rays scan the retina and take an image of it. The image gives the specialist more data about the macula. If the macula has got thicker, or changed in any way, the image is more likely to reveal this.


• A new technique may spot macular degeneration earlier.

What is the treatment for macular degeneration?

Dry AMD

Dry AMD is not curable. Patients with dry AMD will not go completely blind and their peripheral vision will not usually be affected. With the right kind of help, patients can do things to make reading and writing easier.

Low vision clinic - people in the UK with dry AMD are often referred to a low vision clinic. These clinics help patients make the best of what they have. This may include learning how to use magnifying lenses, getting large print books and literature, and using intensive reading lights.

Low-vision rehabilitation appears to improve visual function in macular disease.

Scientists in a study found that post-menopausal women who take hormones have a lower risk of developing macular degeneration.

Wet AMD

There are treatments which can stop the progression of Wet AMD. Anybody with wet AMD must have treatment immediately for it to be effective. Any eyesight lost is very hard to regain. Treatments include:

• Photodynamic therapy - verteporfin, a light-sensitive medication, is injected into the patient's arm. Veteporfin can detect abnormal blood vessels in the macula - it attaches itself to the proteins in the veins. A laser is shone through the eye for about one minute. When verteporfin is activated by the laser, the abnormal blood vessels in the macula are destroyed. This happens without any damage to surrounding eye tissue. If the vessels can be destroyed, blood or fluid cannot leak out and damage the macula any further.
  
  Some patients need photodynamic therapy every few months. Whether this type of treatment is given depends on where the target blood vessels are located and how badly they have affected the macula.


• Anti-VEGF medication (anti vascular endothelial growth factor medication) - VEGF, a chemical, contributes to the formation of new blood vessels which form in the eyes of people with wet AMD. Anti-VEGF drugs block this chemical so that it cannot produce any more blood vessels. Anti-VEGF medication is given by intraocular administration - it is injected into the eye. A very fine needle is used. Before receiving the injection the patient is given an anesthetic. In most cases this treatment is given every few weeks. In the UK the following free anti-VEGF treatments are available: ranibizumab (Lucentis), and bevacizumab (Avastin). Ranibizumab is available free in the UK as long as patients meet certain criteria related to vision. The NHS (UK) has recently stated that pegaptanib is not recommended for use by the NHS for people with wet AMD - this recommendation will not affect people already on that treatment.
  
  In some cases patients given Anti-VEGF medication have had some of their sight restored. Response depends mainly on the patient and his/her own wet AMD characteristics.
  
  Although anti-VEGF treatment does not usually have any side effects, after the injections the patient may experience, pain, swelling, redness and blurred vision.
  
  Serious complications from anti-VEGF, are very rare, and can include damage to the retina, damage to the lens of the eye, and infection.


• Vitamins and minerals - very high doses of vitamins A, C, E and beta-carotene can help slow down AMD progression. The same was found with zinc and copper. Experts say people who are considered to be at high risk of developing AMD should take these supplements. Even though these vitamins and minerals can be bought without a doctor's prescription, patients should discuss taking them with their doctor first. A study carried out by the National Eye Institute reported that high doses of antioxidants slow the progression of AMD or may even prevent it altogether.


• Omega-3 fatty acids - A meta-analysis published in the June issue of Archives of Ophthalmology found that consumption of foods high in omega-3 fatty acids, such as fish and flax, is linked to a reduction in the risk of age-related macular degeneration (AMD)


• Stem-cell therapy - Scientists are looking into using human stem cells to enable the retina to repair itself.


• Robo4 - A study showed that damage was prevented and even reversed when the protein, Robo4, was activated in mice models that simulate age-related macular degeneration (AMD) and diabetic retinopathy.


• Implantable telescope - A report indicated that a two-year Phase II/III IMT002 trial showed substantial visual acuity improvement in End-Stage AMD patients.

Complications

Many people find it difficult to come to terms with partial blindness. What used to be everyday straightforward tasks, such as reading, become frustratingly difficult. Anybody who feels frustrated and emotionally affected by losing some of their eyesight should talk about their feelings with their doctor. If AMD is affecting your daily life, your doctor may be able to refer you to people who can make it easier for you to cope more effectively.

In most countries anybody who is diagnosed with AMD should inform their driving license issuing authorities, as well as their insurance company. Having your central vision affected might affect your driving skills.

A study revealed that people with AMD have a much higher risk of heart attack and stroke.

Charles Bonnet syndrome (visual hallucinations) affect about 12% of people with AMD in the UK. The brain may compensate for visual data it is not receiving by creating fantasy images, often images from memory. Some patients do not tell their doctors about this because they are worried they may have some kind of mental illness. It is important to know that these hallucinations do not reflect the patient's mental state; they are part of the patient's vision problems.

Written by Christian Nordqvist


Copyright: Medical News Today
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