Age-related macular degeneration (AMD): Types, causes, risk factors, and symptoms

Macular degeneration is a disease that affects the retina, a layer at the back of the eyeball. This layer contains light-sensitive cells. It helps us see the world around us.

Age-related macular degeneration (AMD) affects a person’s central vision. Images that used to be clear may start appearing blurred, and dark spots may appear, which get progressively bigger.

Straight lines may appear curved or distorted, and colors are darker or less vivid than they used to be.

It becomes harder to read, write, recognize faces, and drive. However, there is usually enough peripheral vision to allow other activities of daily life. Total vision loss is unlikely.

It affects older adults and is a major cause of partial blindness among people aged 50 years and over.

Types

AMD can lead to a growing loss of central vision as people age.
AMD can lead to a growing loss of central vision as people age.

There are two types of macular degeneration: wet and dry.

Dry macular degeneration: This type develops gradually. There is no treatment. There are things the patient can learn to cope with it. The dry form accounts for 85 to 90 percent of cases.

Wet macular degeneration: Also known as neovascular AMD, this happens when new blood vessels develop under the macula. These can cause blood and fluid to leak. Wet AMD is a more serious form AMD, and severe vision loss can result. It can develop more quickly. If symptoms appear, immediate treatment is needed.

Causes

The exact cause of AMD is not known, but it has been linked to a number of risk factors. These include having excess weight and high blood pressure, smoking, and having a family history of the condition.

Five tips for healthy sightFive tips for healthy sight
Learn about some of the ways you can protect your vision.
Read now

Symptoms

The changes that result from AMD are gradual. Most people do not realize they have it until the later stages, when vision loss starts to occur.

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 AMD symptoms:

Symptoms of dry AMD may not appear for up to 10 years after onset, and longer if AMD affects only one eye.

When symptoms do appear, they may include:

the need for a brighter light when reading

written or printed texts appearing blurry

slow recovery of visual function after exposure to bright light

colors seeming less vibrant than they used to

increasing difficulty recognizing people’s faces

hazier, less defined vision

Wet AMD symptoms:

Eye disease simulation, normal vision
Seeing the two boys with normal vision.

Eye disease simulation, age-related macular degeneration
How a person with AMD sees the same two boys.
Photos by National Eye Institute

All the above symptoms may be present, and also the following:

metamorphopsia, in which straight lines appear crooked or wavy

a blind spot in the central vision (central scotoma) that will get bigger without treatment

Symptoms appear and progress more rapidly than with dry AMD.

According to the National Eye Institute (NEI), early AMD does not always progress to the later stages.

Among those with early AMD in one eye, where the other eye is not affected, around 1 in 20 will have advanced AMD after 10 years.

Around 14 percent of people with early AMD in both eyes will have late AMD in one or both eyes after 10 years.

Regular eye tests can help detect early AMD, and steps can be taken to reduce the risk of it progressing.

Diagnosis

Diagram of the eye
The macula is at the center of the retina and provides the most detailed central vision.

If vision problems start to occur, it is important to see an eye doctor, an optometrist, or an ophthalmologist.

The eye specialist will examine the 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 looks at a special grid, which consists of vertical and horizontal lines. If AMD is present, some of the lines on the grid may seem distorted, broken, or faded.

The result will give a better idea of how much damage has occurred. Most people with detectable symptoms find the lines nearest the center of the grid seem distorted, faded, or broken.

Fluorescein angiography: This test confirms the type of AMD. It is usually carried out if the specialist suspects wet AMD.

Leave a Reply

Your email address will not be published. Required fields are marked *