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Age-related Macular Degeneration

Age-related Macular Degeneration - What it is

Age-related Macular Degeneration (AMD) is a chronic irreversible medical condition that results in vision loss in the centre of the visual field (the macula) because of damage to the retina.

This condition may make it difficult for the patient to read, recognise faces or drive safely. Peripheral vision remains intact for most people, allowing them to remain independent for most daily activities.

AMD is one of the leading causes of blindness affecting those 50 years or older. Studies from the Singapore Eye Research Institute (SERI) have shown that smokers are four times more likely to develop the “wet” or advanced form of AMD than non-smokers.

                             
Normal Vision                


Vision affected by Age-Related
Macular Degeneration

Age-related Macular Degeneration - Symptoms

In early AMD, the impact on vision is generally mild or even non-existent. However, as the disease progresses, symptoms may include:

  • Blurring of central vision (may be gradual or rapid in onset)
  • Shadows or missing areas of vision
  • Distorted vision (e.g. straight lines appear wavy)
  • Problems discerning colours, especially differentiating between similar colours
  • Slow recovery of visual function after exposure to bright light
  •  Loss of contrast sensitivity (ability to tell different levels of brightness apart)

Age-related Macular Degeneration - How to prevent?

There are no proven preventive medications for AMD.

The best way to avoid permanent vision loss is with prompt eye examination and diagnosis by your eye doctor. Early diagnosis improves the treatment success.

A screening tool, the Amsler grid, may help detect subtle changes in your vision. You can monitor your vision daily by looking at an Amsler grid.

You should also eat a balanced diet that includes leafy green vegetables, stop smoking, and protect your eyes from UV light with protective sunglasses or brimmed head gear.


Amsler Grid Chart

Age-related Macular Degeneration - Causes and Risk Factors

What causes AMD?
AMD occurs in “dry” and “wet” forms. 90% of AMD patients suffer from the “dry” form. Dry AMD results in slow progressive loss of central vision. The condition develops as the light-sensitive cells in the macula slowly break down with age.

Wet AMD, also known as exudative or neo-vascular AMD, is caused by the growth of small, abnormal blood vessels under the retina in the macula. Wet AMD usually arises from pre-existing dry AMD.

These abnormal blood vessels leak blood, fluid, lipids and protein, resulting in disruption of the normal structure of the retina. If it is not treated, scar tissue form under the macula and central vision is permanently destroyed. The “wet” form commonly results in advanced visual loss within a short period of time.

 

What puts me at risk of AMD?  
Your risk increases with:
  • Age. A 1997 study showed that one in four people aged 60 and above suffer from the condition in Singapore
  • A positive family history
  • Smoking
  • Obesity
  • Cardiovascular diseases

Age-related Macular Degeneration - Diagnosis

The early stages of AMD usually start without symptoms. Only a comprehensive dilated eye examination can detect AMD. The eye examination may include the following:

  • Amsler Grid
    Your ophthalmologist may ask you to look at an Amsler grid. Changes in your central vision may cause the lines in the grid to disappear or appear wavy, a sign of AMD. This is also used to monitor patients at home for progression.


             Normal Vision             Vision impaired by AMD

    Hold the Amsler grid below at eye level at a comfortable reading distance. If you wear reading lenses, wear them during this test. Cover one eye at a time and focus on the dot in the centre. If you see wavy or fuzzy lines, or if certain squares are missing or appear blurred, you may be displaying symptoms of AMD.

  • Fundus Fluorescein Angiogram (FFA) and Indocyanine Green Angiogram (ICG)
    In this test, a fluorescent dye is injected into a vein in your arm. Pictures are taken as the dye passes through the blood vessels in your eye. This makes it possible to see leaking blood vessels, which occur in the “wet” type of AMD. In rare cases, complications due to the injection can arise, like nausea or more severe allergic reactions.
  • Optical Coherence Tomography (OCT)
    OCT is similar to ultrasound, except the latter uses sound waves to capture images of living tissues. OCT uses light waves and can capture high-resolution cross-sectional images of any tissues that can be penetrated by light, such as the eyes. After your eyes are dilated, you will be asked to place your head on a chin rest and hold still for several seconds while the images are obtained. The light beam is painless.

Age-related Macular Degeneration - Treatments

If you have been diagnosed with wet AMD, treatment is usually necessary as the condition may worsen over the next few weeks. It may lead to irreversible vision loss.

While treatment can stabilise vision, the degree of improvement will depend on how early the disease is detected and response to treatment.

Intravitreal injections (drugs injected into the eye)
Currently, the most common treatment is in the form of drugs injected into the eye. Avastin*, Lucentis and Eylea are some drugs used to treat wet AMD as they block the growth of abnormal blood vessels. The injection can be performed safely after the eye has been anaesthetised with eye drops. You will experience some mild discomfort after the injection.
*Avastin is accepted by all public hospitals and institutions for treatment of AMD.

However, the effect of each injection would usually last for one month and a long course of repeated injections is required to adequately control the condition. Clinical studies have suggested that at least 12 to 14 injections will be required over a two-year period to control the disease. During this time, your eye condition should be reviewed frequently as response can vary between individuals. Your ophthalmologist will also need to repeat the OCT scan at most visits, and the angiogram periodically to assess your response.


Illustration: Intravitreal Injections
of Anti-VEGF Agents

Other treatment options (usually used in combination)
In some selected cases, other forms of treatment, with or without injections may also be recommended by your ophthalmologist. Photodynamic therapy uses a non-thermal laser together with an intravenous drug (verteporfin) to reduce leakage and seal up abnormal blood vessels. Laser photocoagulation uses a hot laser to destroy the abnormal blood vessels.

For dry AMD, there is currently no known treatment, but supplements may help slow down the progression in high-risk eyes. Early detection of conversion to the wet type is also important for better preservation of vision.

Age-related Macular Degeneration - Preparing for surgery

Age-related Macular Degeneration - Post-surgery care

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