Age-related macular degeneration, often called ARMD or AMD, is the leading cause of vision loss among Americans 65 and older.
AMD causes damage to the macula, which is the central portion of the retina responsible for sharp central vision. AMD doesn't lead to complete blindness because peripheral vision is still intact, but the loss of central vision can interfere with simple everyday activities such as reading and driving, and it can be very debilitating.
Types of Macular Degeneration
There are two types of macular degeneration: Dry AMD and Wet AMD.
Dry (non-exudative) macular degeneration constitutes approximately 85-90% of all cases of AMD. Dry AMD results from thinning of the macula or the deposition of yellow pigment known as drusen in the macula. There may be gradual loss of central vision with dry AMD, but it is usually not as severe as wet AMD vision loss. However, dry AMD can slowly progress to late-stage geographic atrophy, which can cause severe vision loss.
Wet (exudative) macular degeneration makes up the remaining 10-15% of cases. Exudative or neovascular refers to the growth of new blood vessels in the macula, where they are not normally present. The wet form usually leads to more serious vision loss than the dry form.
AMD Risk factors
- Age is the biggest risk factor. Risk increases with age.
- Smoking. Research shows that smoking increases your risk.
- Family history. People with a family history of AMD are at higher risk.
- Race. AMD is more common in Caucasians than other races, but it exists in every ethnicity.
- Gender. AMD is more common in women than men.
Detection of AMD
There are several tests that are used to detect AMD.
A dilated eye exam can detect AMD. Once the eyes are dilated, the macula can be viewed by the ophthalmologist or optometrist. The presence of drusen and pigmentary changes can then be detected.
An Amsler Grid test uses pattern of straight lines that resemble a checkerboard. It can be used to monitor changes in vision. The onset of AMD can cause the lines on the grid to disappear or appear wavy and distorted.
Fluorescein Angiogram is a test performed in the office. A fluorescent dye is injected into the arm and then a series of pictures are taken as the dye passes through the circulatory system in the back of the eye.
Optical coherence tomography (OCT) is a test based on ultrasound. It is a painless study where high-resolution pictures are taken of the retina.
Article contributed by Jane Pan M.D.
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