Macular Degeneration is presently considered an incurable eye disease, and is the leading cause of vision loss – it affects more people than glaucoma and cataracts combined. Macular degeneration affects over 10 million Americans.
The macula is the central and most sensitive area of the part of the eye that “sees.” In a healthy eye, the macula records detailed images and sends them up the optic nerve to the brain, so they can be recorded as “sight.” As the macula deteriorates, the quality of these images is affected. At first, there may be little to no change in sight. But as the disease progresses, central vision may become blurry or wavy, and eventually central vision may be completely lost, leaving the patient with only their peripheral vision. At these advanced stages, patients may be considered legally blind.
Types of Macular Degeneration
There are two basic types of macular degeneration: “wet,” or exudative, which affects approximately 10-15% of patients, and the far more common type which is “dry,” or atrophic, which affects 85-90%.
There is also a third type which is much less common and occurs in children, called Stargardt disease.
Wet (exudative) Macular Degeneration
In this type, abnormal blood vessels known as CNV (choroidal neovascularization) grow under the macula and retina. After a while, the new blood vessels can bleed or leak fluid, causing a bulge which lifts the macula from its normally flat position. For people with “wet” macular degeneration, this is the cause of their distorted or lost central vision. In these cases, vision loss can be rapid and severe.
Dry (atrophic) Macular Degeneration
In this type, small yellow deposits known as drusen form under the macula. This leads to a thinning and drying of the macula in the areas where the drusen are present. This causes the macula to lose its function, and the patient to lose his or her central vision.
An interesting fact: nearly all people over the age of 50 have at least one small drusen in one or both eyes. However, only eyes with large drusen are at risk for “dry” macular degeneration.
This type of macular degeneration is much more common than the “wet” type, and progresses much more slowly. In some cases, people with the “dry” type can develop the “wet” type over time.
This type of macular degeneration is passed down genetically from the parents. It develops in children ages 6-20. “Stargardt Disease is the result of a gene called ABCA4 and is usually a recessive trait. When both parents carry the ABCA4 mutation, there is a 25 percent chance their children will have Stargardt disease.”
What happens in Stargardt disease is that flecks of waste material build up in the nutritional support layer (RPE) for the rods and cones of the retina, causing all three to break down and impair vision.
Stages of Macular Degeneration
There are three stages of age-related macular degeneration (AMD).
Most patients do not experience vision loss at this stage. This highlights the need for regular eye exams, so that onset can be detected by your ophthalmologist. In the early stage, AMD is diagnosed by the presence of medium-sized drusen (yellow deposits beneath the retina.)
At this stage there may be some vision loss in some patients; others still may not notice any symptoms. A comprehensive eye exam with specific tests will look for larger drusen and/or pigment changes.
Vision becomes noticeably impaired at this stage.
Macular Degeneration Risk Factors
The most important risk factors for macular degeneration are:
The largest risk factor for AMD is age. Those who are 55 or older are most likely to experience AMD, and your risk factor increases as you age.
If you have a family history of AMD, you are at a higher risk. For Stargardt disease, you are at risk if both your parents carry a recessive gene.
Caucasians are more likely to develop AMD than African-Americans and Latinos.
Smoking Cigarettes doubles (!) your risk of developing AMD.
There is currently no known cure for AMD, but there are things you can do to keep your eyes as healthy as possible. Staying healthy will reduce your risk of developing AMD and might even slow the disease’s progression once it has developed. Don’t smoke, get enough exercise, eat healthy, get enough sleep, and wear sunglasses to protect your eyes from ultraviolet light.
Read about some promising new treatments for AMD here.
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