Macular Degeneration, Age-Related
What is it?
The macula is the central and most sensitive portion of the retina, the layer of tissue in the back of the eye that contains the light-receptive cells essential for sight. After age 50, the macula may show signs of age-related macular degeneration (AMD). In AMD, central vision and the ability to distinguish fine detail may become increasingly impaired, but peripheral vision remains unaffected. If macular function is lost completely, activities such as reading become quite difficult without the assistance of low vision aids. There are two forms of AMD: "dry" (also known as nonneovascular or atrophic) and "wet" (neovascular). About 90 percent of those with AMD have the dry form. Although irreversible, many patients with dry AMD may not experience any symptoms or may only experience gradual and minimal changes in their vision clarity. A small fraction of people with dry AMD experience severe vision loss. In wet AMD, however, fine blood vessels at the back of the eye proliferate and leak fluid and blood. This neovascular tissue leads to dense scarring of the macula with permanent, significant central vision loss within weeks to months.Wet AMD may develop suddenly in patients with dry AMD. Both forms are painless and the condition typically affects both eyes. AMD is the leading cause of severe and irreversible vision loss in older Americans.
What Causes It?
- The cause is unknown, although aging is clearly a risk factor. Some evidence of AMD can be detected in approximately one-quarter of all people over the age of 65 and in one-third of those over age 80.
- Other risk factors include hyperopia (farsightedness), cigarette smoking, light-colored eyes, and a family history of AMD. High blood pressure, lifetime sunlight exposure, dietary factors, and genetic susceptibility may increase wet AMD risk.
Prevention
- Daily ingestion of high-dose micronutrient supplements that contain vitamins C, E, beta carotene, zinc, and copper can reduce the frequency at which patients with earlier dry forms of AMD may progress to the vision-involving forms of advanced AMD.
- Avoidance of smoking and treatment of hypertension might help prevent the disorder.
Diagnosis
- Dilated eye examination by an ophthalmologist is needed.
- Wet AMD is confirmed with fluorescein angiography (injection of a special dye into the bloodstream to allow clear photographic images of the blood vessels in the eye to be taken).
How to Treat It
- Individuals with large age-related deposits called drusen, those with regions of atrophic tissue, or any individual who has experienced vision loss in one eye from AMD should discuss vitamin and mineral supplementation with their ophthalmologist.
- People with dry AMD should be monitored for the onset of wet AMD.
- Self-monitor vision by testing each eye individually for distorted vision or blank central spots. See a doctor immediately if new symptoms emerge.
- If detected early enough, wet AMD may be treated with laser surgery or photodynamic therapy. These treatments aim to destroy the new leaking blood vessels and minimize growth and further vision loss. Such surgery should be performed only by an ophthalmologist with special training and experience in the procedure.
- New treatments being tested include new lasers, surgery to remove or move abnormal vessels, and new drugs that may control new vessel growth. Retinal cell transplants do not yet work, but may hold promise for future generations.
- Careful follow-up is essential for all AMD patients
- Low-vision optical aids may be useful, including: high-power reading glasses; a small telescope mounted on one lens of your eyeglasses; a pocket telescope for reading street signs; and a closed-circuit television hookup that can magnify a written page as much as 60 times and display the image on a television screen.
When to Call a Doctor
- See an ophthalmologist promptly if you have blurred or distorted central vision.
- A simple home test (the Amsler grid) can help monitor visual changes. Any worsening of vision warrants an immediate visit to an ophthalmologist.
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Copyright © 2008 Medletter Associates, LLC
Content excerpted from Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference.