AMD: AN OVERVIEW OF THE DISEASE

What Is Macular Degeneration?

The macula is the small central portion of the retina that allows one to see details clearly and perform activities such as reading, driving, and recognizing faces. Macular degeneration is the deterioration or breakdown of the macula.When the macula is compromised, problems with central vision — such as blurriness, dark areas or distortion — can occur.

There are different kinds of macular degeneration, but Age-Related Macular Degeneration (AMD) is the most common. AMD is a leading cause of severe vision loss in Americans age 50 and over.

How Does AMD Affect Vision and Ability?

AMD affects the ability to see centrally both far and near; but, in most cases, it does not have an impact on peripheral vision. For instance, someone with AMD might be able to see the numbers on the edge of a clock but  not be able to see the clock’s hands.It is common for individuals with AMD to have localized areas of vision loss, called scotomas that result from only some parts of the macula being damaged.

AMD can occur in one eye at first. Typically both eyes will be affected to some degree, although the disease may not develop in each eye at the same time and may not progress in each eye at the same rate. Approximately 43 percent of people with wet AMD in one eye progress to wet AMD in both eyes within five years.9

AMD can result in legal blindness (20/200 in the better eye), although it almost never results in total blindness. The majority of people with advanced AMD retain normal peripheral vision and through rehabilitation can continue to care for themselves, read and perform many daily activities independently.

Since visual acuity of 20/40 is required for driving in many states, many people with early vision loss from AMD may be unable to continue driving.  Some communities offer alternative transportation programs, and the availability of individual sidewalk vehicles is increasing.

How Prevalent Is AMD, Who Has It and Who Is at Risk for Developing It?

• Advanced dry or wet AMD has caused at least some vision loss in an estimated 1.75 million Americans. 10
• Greater than 7 million more people have earlier stages of the disease.11
• 200,000 new cases of the more rapidly progressive type of AMD (called wet AMD) are diagnosed in the United States each year.12
• AMD is far more common in people over the age of 50, although some types of macular degeneration affect people at a younger age.
• Due in part to their longer life expectancy,13 women appear to be at greater risk of developing the disease than men, accounting for 63 percent of the total cases of AMD in the United States.14
• In the United States, AMD can occur in all ethnic groups; however, it is far more prevalent in Caucasians. It is lower in darkly pigmented individuals.15
• The rise in overall life expectancy indicates that an increase in the number of cases of AMD – like other diseases of aging – can be expected, creating a significant public health issue.16
• The number of persons having AMD will increase by 50% to 2.95 million in 2020. 10

What Causes AMD?

• Why AMD develops is not yet known, but it is clearly related to the aging process.  It may be caused in part by hereditary and environmental factors.
• New evidence indicates that as many as 43% of patients with AMD have a genetic mutation in the Complement factor H gene.17-19
• There is also the possibility that untreated health problems, such as hypertension, might eventually contribute to the degeneration of the macula.20

 What Are the Two Major Categories of AMD?

Atrophic or non-neovascular AMD – referred to as “dry AMD” – is characterized by the aging and thinning of macular tissues, and it usually results in gradual vision loss.

Exudative or neovascular AMD – also known as “wet AMD” – results when abnormal blood vessels form underneath the central retina at the back of the eye. These new blood vessels leak fluid or blood, causing central vision to blur. Wet AMD accounts for only about 10 percent of AMD cases, but it progresses at a more rapid pace than dry, and accounts for an estimated 90 percent of the severe vision loss that is associated with the disease, although a significant number of people reach the end stage (i.e., severe vision loss) of dry AMD as well.21