Macular degeneration is a progressive eye disease that affects the sharp central vision you need for important activities like driving and reading. It is caused by damage to the macula, a part of the light-sensitive retina at the back of the eyeball. The retina is responsible for picking up images and transmitting them as electrical impulses to the brain.
The most common form of macular degeneration develops as a person ages and is referred to as age-related macular degeneration (AMD). AMD is one of the leading causes of severe vision loss in people age 40 years and older. AMD usually goes undetected until it reaches the advanced stage, since the intermediate form of the disease is typically asymptomatic. At the advanced stage, noticeable changes in central vision become apparent, such as blurring, waviness, or a loss of colour.
The deterioration in the eye has progressed to the point where blind spots are usually noticeable; eventually there’s a complete loss of central vision. AMD almost never results in complete blindness.
People with the advanced stage of the disease almost always retain their peripheral vision. There are two types of age-related macular degeneration: dry AMD and wet AMD. About 85 percent to 90 percent of people have the dry type, which occurs when the retina begins to thin and deteriorate, and deposits of debris form under the macula.
The much more severe wet type occurs when abnormal blood vessels form under the macula and leak fluid. There is no cure for AMD, but a number of treatments are available that can slow the progression of the disease and restore some lost vision. The appropriate treatment depends on the stage of the disease and whether the AMD is in the wet or dry form. While both forms can lead to vision loss, wet AMD usually progresses faster and is more likely to result in advanced-stage AMD. All AMD begins as the dry form.
Causes
Although the exact cause of age-related macular degeneration is unknown, doctors have a good understanding of how the condition progresses once it begins to develop. AMD begins in its dry form, which occurs when the retina begins to thin and deteriorate, and deposits of debris form under the macula, blurring or distorting vision. If the dry form progresses into the advanced stage, with significant cell death and atrophy, it can cause vision loss.
The dry form can also turn into the wet form of AMD, which is usually more severe. The wet type occurs when abnormal blood vessels form under the macula and leak fluid; those who develop the wet form make up the majority of patients who experience serious vision loss from the disease. It’s impossible to predict whether any individual with the dry form will end up with the wet form, so it is very important for people with AMD to monitor their eyesight carefully and visit their eye doctor on a regular basis.
Risk factors
Most people develop AMD in middle age, and the risk increases with age. According to the American National Eye Institute, additional risk factors include smoking, obesity, race, family history, and gender. Research has hinted at a connection between being obese and progressing from early and intermediate AMD to advanced AMD.
(US News and World Report)
|
E-mail