What Is Age-Related Macular Degeneration?
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. AMD is the leading cause of severe and irreversible vision loss in older Americans.
There are two forms of AMD: “dry” (also known as non-neovascular or atrophic) and “wet” (neovascular). About 90% 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 some people with dry AMD, macular degeneration progresses to the wet form, which is considered to be advanced AMD. In wet AMD, fine blood vessels at the back of the eye proliferate and leak fluid and blood into surrounding tissue, and this neovascular tissue leads to dense scarring of the macula, with permanent, significant central vision loss occurring 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, but dry AMD can occur in one eye only—in which case you may not initially notice any changes in overall vision.
Who Gets Age-Related Macular Degeneration?
AMD occurs in about 10% of people over the age of 50, and about 33% of people over 75. AMD is most common in Caucasians of European decent and is more prevalent in women. About 1.8 million Americans are affected. Every year 200,000 people with AMD suffer complete loss of central vision in one or both eyes.
- Dry AMD often has no symptoms in early stages
- Dry AMD in late stages: a blurry spot in center of vision and increasingly blurred central vision
- Haziness, grayness, trouble or inability to recognize people’s faces
- An early symptom of wet AMD is visual distortion: straight lines appear wavy; objects may appear smaller than in actuality; areas of the central vision disappear or are missing.
- Loss of central vision
- Difficulty with reading, doing close work, or driving.
- Symptoms of wet AMD typically appear and worsen fairly quickly
- 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.
What If You Do Nothing?
Early-stage dry AMD may stabilize, but it can also become advanced. Wet AMD is likely to lead to vision loss without treatment.
- Dilated eye examination by an ophthalmologist is performed using an ophthalmoscope or slit-lamp biomicroscope to magnify and examine the back of the eye, the location of the retina and macula. Non-neovascular AMD is diagnosed when the doctor sees drusen—yellowish deposits underneath the retina that are characteristic of AMD— or other pigment changes in the macula. A diagnosis of neovascular AMD is suspected when an individual experiences new symptoms and ophthalmoscopy shows fluid, blood, lipid (fat) deposits, or other changes in the area of the macula.
- 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).
- There is no treatment to cure or reverse dry AMD. However, individuals with intermediate-stage dry AMD—those with large drusen, with regions of atrophic tissue, or any individual who has experienced vision loss in one eye from dry AMD—should talk to their doctor about taking a specific vitamin and mineral formula that may reduce their risk of dry AMD progressing to the wet form (see Prevention).
- Anyone with dry AMD should be monitored for the onset of wet AMD.
- You can also self-monitor your vision by testing each eye individually for distorted vision or blank central spots. See a doctor immediately if new symptoms emerge.
- Wet AMD can be treated with drugs that may reduce the growth and leakiness of abnormal blood vessels. Called VEGF inhibitors, these drugs—which include Lucentis, Avastin, and Eylea—are administered by intraocular injection on a monthly or an as-needed basis. Studies have shown that 90 to 95% of patients treated with VEGF inhibitors maintain or even improve their vision, and the drugs are now the standard of care for patients with wet AMD.
- Another option for treating wet AMD, especially when the condition is resistant to drug therapy, is photodynamic therapy, which aims 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.
- 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.
- Daily ingestion of high-dose micronutrient supplements can reduce the frequency at which patients with intermediate-stage AMD may progress to the vision-involving forms of advanced AMD. A formulation known as AREDS—which contains vitamins C, E, beta carotene, zinc, and copper—was shown in a study by that name to benefit many patients with dry AMD. A similar formulation—AREDS2, which also contains lutein and zeaxanthin—is also available. Both are marketed under several different brand names. They are recommended only for people who already have dry AMD at an intermediate stage in one or both eyes, or advanced dry AMD in one eye with the other eye at risk of disease progression. There is no proven benefit for people with early-stage AMD. And there is no evidence that taking the supplements will prevent AMD from developing in healthy eyes.
- Avoidance of smoking, treatment of hypertension, and reducing exposure to sunlight might help prevent the disorder or keep it from progressing.
When To Call Your 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.
Reviewed by Daniel E. Bustos, M.D., M.S., Private Practice specializing in Comprehensive Ophthalmology in Nashville, TN. Review provided by VeriMed Healthcare Network.