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Glossary of Eye terms

 

 

Age-Related Macular Degeneration

What is age-related macular degeneration?

Age-related macular degeneration (AMD) is a common eye disease associated with aging that results from deterioration of the macula. It gradually destroys sharp, central vision, which is the ability to distinguish details and shapes of objects. In some people, AMD advances so slowly that it has little effect on their vision as they age. In others, the disease progresses faster and may lead to a loss of vision in one or both eyes.

It is the leading cause of visual impairment in elderly people in the United States. An estimated 2 percent of those in their 50s, and 30 percent of those older than 75, will get the disease. Already, some 10 million Americans, most in their 60s and 70s, are affected by the condition.

What is the macula?

It is a tiny area in the middle of the retina. The macula is made up of millions of light-sensing cells that help to produce central vision.

Are there different types of AMD?

Yes. There are two:

• Dry AMD: Ninety percent of all people with AMD have this type. Scientists are still not sure what causes dry AMD. Studies suggest that an area of the retina becomes diseased, leading to the slow breakdown of light-sensing cells in the macula and a gradual loss of central vision.
  
• Wet AMD: Although only 10 percent of all people with AMD have this type, it accounts for 90 percent of all blindness from the disease. As dry AMD worsens, new blood vessels may begin to grow and cause "wet" AMD. Because these new blood vessels tend to be very fragile, they will often leak blood and fluid under the macula. This causes rapid damage to the macula that can quickly lead to the loss of central vision.

Who is most likely to get AMD?

The greatest risk factor is age. Although AMD may occur during middle age, studies show that people over age 60 are clearly at greater risk than other age groups.

Besides age, what are some other AMD risk factors?

• Gender: Women tend to be at greater risk for AMD than men.

• Race: Caucasians are much more likely to lose vision from AMD than African Americans.

• Smoking: Smoking may increase the risk of AMD.

• Family History: Those with immediate family members who have AMD are at a higher risk of developing the disease.

What are the symptoms?

The most common early sign of dry AMD is blurred vision.

As fewer cells in the macula are able to function, people will see details less clearly in front of them, such as faces or words in a book.

Often this blurred vision will go away in brighter light.

As the loss of these light-sensing cells increases, people may see a small -- but growing -- blind spot in the middle of their field of vision.

The classic early symptom of wet AMD is that straight lines appear crooked. This results when fluid from the leaking blood vessels gathers and lifts the macula, distorting vision. A small blind spot may also appear in wet AMD, resulting in loss of one's central vision.

How is it detected?

Your eye doctor may suspect AMD if you are over age 60 and have had recent changes in your central vision. To look for signs of the disease, he or she will use eye drops to dilate, or enlarge, your pupils. Dilating the pupils allows your eye doctor to view the back of the eye better.

You may also be asked to view an Amsler grid, a pattern that looks like a checkerboard. Early changes in your central vision will cause the grid to appear distorted, a sign of AMD.

How can it be treated?

No treatment now exists for dry AMD. It has been suggested that taking certain extra vitamins and minerals may slow the progress of the disease. But this treatment needs much more research before scientists can know for sure if it's helpful.

Some cases of wet AMD can be treated with laser surgery. This involves aiming a strong light beam onto the new blood vessels to destroy them.

What can you do to protect your vision from age-related macular degeneration?

Although there is no effective treatment for dry AMD at this time, it is crucial that those who progress to wet AMD and need laser surgery have it before the disease destroys central vision.

If you have dry AMD or are age 60 or older, you should have your eyes examined through dilated pupils at least once a year. You may also want to get an Amsler grid from your eyecare professional to check your vision at home.

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Excerpted from: National Eye Institute ©2005

 

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