More than 10 million Americans suffer the potentially disabling effects of macular degeneration, an eye disease that is the top cause of vision loss in people over age 55.
The incurable condition, which blurs central vision, is also called age-related macular degeneration (AMD) because it is associated with growing older, according to the National Eye Institute (NEI). Central vision is needed for driving, reading and recognizing faces and colors, among other tasks.
The macula is located in the center of the retina, the inside back layer of the eyeball that converts light and images into electrical signals that are sent to the brain. AMD can occur in one or both eyes.
AMD typically develops gradually and isn't painful, so early symptoms can be mistaken for normal age-related vision changes. According to the Mayo Clinic, symptoms include:
- Straight lines or faces appearing wavy
- Doorways seeming crooked
- Objects appearing smaller or farther away
- Increasing difficulty adapting to low light levels
- Decreasing color intensity or brightness
- Difficulty recognizing faces
- Increasing vision haziness
- Blurry or blind spots in central vision
Causes & Complications
The exact causes of AMD aren't known, but certain physical conditions and lifestyle choices increase the odds of developing it. According to the NEI, these risk factors include:
- Family history
- High blood pressure
- High cholesterol
- Being Caucasian
- Being female
- Diet low in fruits and vegetables
There are two types of AMD: wet and dry.
Wet AMD is relatively rare, comprising only about 15 percent of all cases, according to the NEI. It is also more serious than dry AMD, and can trigger rapid vision loss. It develops when abnormal blood vessels behind the retina begin emerging under the macula, and leaking blood and fluid.
Dry AMD occurs when light-sensitive cells in the macula gradually deteriorate. The size and number of yellow deposits behind the retina called drusen, which dislodge the macula from its usual spot, often indicate how severe dry AMD has become. When drusen are numerous or large, dry AMD is usually more advanced, according to the NEI.
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Diagnosis & Tests
AMD is suspected in people over 60 who experience recent changes in the center of their field of vision. Several tests can help confirm the diagnosis, including:
- Dilated eye exam: The patient's pupils are dilated with eye drops so the optic nerve and retina can be examined using a special magnifying lens, according to the Mayo Clinic. Sometimes a mottled effect is observed, which indicates the presence of drusen.
- Amsler grid: Patients look at this grid, which resembles a checkerboard with a black dot in the center. If straight lines appear wavy or some lines appear to be missing, AMD is more likely.
- Angiogram: A special camera takes pictures of the eye after colored dye is injected into an arm vein, which then travels to blood vessels in the eye. AMD may be present if images show blood vessel or retinal irregularities.
- Tomography: Retinal thinning or thickening associated with AMD can be viewed with this non-invasive imaging test, according to the Mayo Clinic.
Treatments & Medication
While nothing cures AMD, various treatments are available depending on its type.
The progression of dry AMD from intermediate to advanced may be slowed by taking a daily high-dose combination of antioxidant vitamins and zinc, according to the NEI. The formulation includes:
- 500 mg of vitamin C
- 400 IU of vitamin E
- 15 mg of beta carotene (often labeled as equivalent to 25,000 IU of vitamin A)
- 80 mg of zinc (as zinc oxide)
- 2 mg of copper (as cupric oxide)
Wet AMD has three main treatments, not all of which are appropriate for every patient. They include:
- Laser surgery, which destroys leaky blood vessels behind the retina
- Injections into the eye with a drug that blocks a growth factor stimulating abnormal blood vessel development
- Photodynamic therapy, which includes the injection of a light-activated drug into the bloodstream. After the injection, a light is shined into the eye for 90 seconds, causing the drug to destroy new blood vessel growth, according to the NEI.
Several lifestyle changes can help AMD patients cope better with resulting vision loss, according to the Mayo Clinic. These include using magnifying lenses and glasses; adjusting computer font size and brightness level; using adaptive appliances such as clocks and telephones with extra-large numbers; and brightening room light levels.