Macular Degeneration

Macular Degeneration Overview

Macular degeneration is a disorder that includes a variety of eye diseases that affect central vision. Central vision is what you see directly in front of you rather than what you see at the side (or periphery) of your vision.

Macular degeneration is caused when part of the retina deteriorates. The retina is the interior layer of the eye. The macula is the central portion of the retina and is responsible for detailed vision.

Age-related macular degeneration is the most common type of macular degeneration and is the leading cause of legal blindness in people older than 55 years in the United States. The disease affects more than 10 million Americans, including 23% of Americans older than 90 years. Because overall life expectancy continues to increase, age-related macular degeneration has become a major public health problem.

There are 2 types of age-related macular degeneration:

• Dry (atrophic) form: Multiple, small, round, yellow-white spots called drusen are the key identifiers for the dry type. The spots are located in the back of the eye at the level of the outer retina. Spots typically become visible when a person reaches his or her late 30s or older. People with these spots may have excellent vision and no symptoms. Most people with age-related macular degeneration begin with the dry form.
• Wet (exudative) form: In the wet form, newly created abnormal blood vessels grow under the center of the retina. These blood vessels leak, bleed, and scar the retina, distorting vision or destroying central vision. Vision distortion usually starts in one eye and may affect the other eye later.
• Wet macular degeneration affects only 10% of people who have age-related macular degeneration but accounts for two thirds of the people who have significant visual loss.
  
• More than 200,000 new cases of wet age-related macular degeneration occur each year in the United States.

Macular Degeneration Causes

No one knows the causes of age-related macular degeneration. Causes are likely to be genetically inherited, but environmental factors also contribute. Macular degeneration often runs in families. A recent study of twins showed that genetic factors play a significant role in the cause.

Many of the following risk factors have been found to be associated with age-related macular degeneration:

• Age: The likelihood to develop macular degeneration increases with age.
• Race: Macular degeneration is more common in whites but occurs in all races.
• Smoking
• High blood pressure
• Vascular disease
• High intake of saturated fat and cholesterol
• High blood cholesterol level
• Farsightedness (hyperopia)
• Exposure to sunlight
• Family history

Macular Degeneration Symptoms

Symptoms of age-related macular degeneration include the following:

• Blurred or decreased central close-up and distance vision
• Blind spots
• Straight lines looking irregular or bent, and objects appearing a different color or shape in each of the eyes