Age-related macular degeneration (AMD) is a term which describes a wide spectrum of eye findings. The disease is associated with aging, and gradually affects sharp, central vision. Central vision is needed for seeing objects clearly and for common daily tasks such as reading and driving. AMD affects the macula, the part of the retina that provides central vision and allows you to see fine detail. In some cases, AMD advances so slowly that people notice little change in their vision. In others, the disease progresses faster and may lead to a loss of vision in both eyes. AMD is a leading cause of painless vision loss in Americans 60 years of age and older.
Dry AMD occurs when the light-sensitive cells in the macula slowly break down, gradually blurring central vision in the affected eye. As dry AMD gets worse, you may see a blurred spot in the center of your vision. Over time, as less of the macula functions, central vision is gradually lost in the affected eye. The most common symptom of dry AMD is slightly blurred central vision. You may have difficulty recognizing faces. You may need more light for reading and other tasks. Dry AMD generally affects both eyes, but vision loss may be more severe in one eye than the other.
During your comprehensive dilated eye exam, your ophthalmologist examines the macula for signs of AMD. In mild cases this may be seen as a mild disturbance in the normal pigment layer which is underneath the macula. In some cases, drusen develop. Drusen are yellow deposits under the retina. They often are found in people over age 60. Drusen alone do not usually cause vision loss. In fact, scientists are unclear about the connection between drusen and AMD. They do know that an increase in the size or number of drusen raises a person's risk of developing either advanced dry AMD or wet AMD. These changes can cause serious vision loss. Dry AMD has three stages, all of which may occur in one or both eyes:
If you have vision loss from dry AMD in one eye only, you may not notice any changes in your overall vision. With the other eye seeing clearly, you still can drive, read, and see fine details. You may notice changes in your vision only if AMD affects both eyes. Ninety percent of all people with AMD have dry AMD. The Cause is not known
Wet AMD is the more rapidly progressing form of AMD. Generally it occurs in people with prior signs of dry AMD. In wet AMD abnormal blood vessels form behind the retina and start to grow under the macula. These new blood vessels tend to be very fragile and often leak blood and fluid. The blood and fluid separate the macula from its normal position in the back of the eye. With wet AMD, loss of central vision can occur quickly. Wet AMD is less common than dry AMD, but more commonly leads to severe central vision loss. An early symptom of wet AMD is that straight lines appear wavy. If you notice this condition or other changes to your vision, contact your eye care professional immediately.
Risk factors for AMD include age. Although AMD may occur during middle age, studies show that people over age 60 are clearly at greater risk than other age groups. Other risk factors include:
Treatment for wet AMD includes laser surgery, photodynamic therapy, and injections into the eye. None of these treatments is a cure for wet AMD. The disease and loss of vision may progress despite treatment.
Wet AMD can now be treated with new drugs that are injected into the eye (anti-VEGF therapy). Abnormally high levels of a growth factor called VEGF occur in eyes with wet AMD and promote the growth of abnormal new blood vessels. This drug treatment blocks the effects of the growth factor. You will need multiple injections that may be given as often as monthly. The eye is numbed before each injection. After the injection, you will remain in the doctor's office for a while and your eye will be monitored. This drug treatment can help slow down vision loss from AMD and in some cases improve sight. Medications include Macugen, Avastin, and Lucentis.
In photodynamic therapy, a drug called verteporfin is injected into your arm. It travels throughout the body, including the new blood vessels in your eye. The drug tends to "stick" to the surface of new blood vessels. Next, a light is shined into your eye for about 90 seconds. The light activates the drug. The activated drug destroys the new blood vessels and leads to a slower rate of vision decline. Unlike laser surgery, this drug does not destroy surrounding healthy tissue. Because the drug is activated by light, you must avoid exposing your skin or eyes to direct sunlight or bright indoor light for five days after treatment. Photodynamic therapy is relatively painless. It takes about 20 minutes and can be performed in a doctor's office. Photodynamic therapy slows the rate of vision loss. It does not stop vision loss or restore vision in eyes already damaged by advanced AMD. Treatment results often are temporary. You may need to be treated again.
Laser surgery uses a laser to destroy the fragile, leaky blood vessels. A high energy beam of light is aimed directly onto the new blood vessels and destroys them, preventing further loss of vision. However, laser treatment also destroys some surrounding healthy tissue and some vision. Only a small percentage of people with wet AMD can be treated with laser surgery. The risk of new blood vessels developing after laser treatment is high. Repeated treatments may be necessary. In some cases, vision loss may progress despite repeated treatments.
There is no treatment for advanced dry AMD. However, treatment can delay and possibly prevent intermediate AMD from progressing to the advanced stage, in which vision loss occurs. However, the National Eye Institute's Age-related Eye Disease (AREDS) study found that taking a specific high-dose formulation of antioxidants and zinc significantly reduces the risk of advanced AMD and its associated vision loss. Slowing AMD's progression from the intermediate stage to the advanced stage will save the vision of many people. People who are at high risk for developing advanced AMD should consider taking the formulation. You are at high risk for developing advanced AMD if you have either:
Your ophthalmologist can tell you if you have AMD, its stage, and your risk for developing the advanced form.
The AREDS formulation is not a cure for AMD. It will not restore vision already lost from the disease. However, it may delay the onset of advanced AMD. It may help people who are at high risk for developing advanced AMD keep their vision.
If you are already taking daily multivitamins and your doctor suggests you take the high-dose AREDS formulation, be sure to review all your vitamin supplements with your doctor before you begin. Because multivitamins contain many important vitamins not found in the AREDS formulation, you may want to take a multivitamin along with the AREDS formulation.
If you have dry AMD, you should have a comprehensive dilated eye exam at least once a year. Your ophthalmologist can monitor your condition and check for other eye diseases. Also, if you have intermediate AMD in one or both eyes, or advanced AMD in one eye only, your doctor may suggest that you take the AREDS formulation containing the high levels of antioxidants and zinc.
Because dry AMD can turn into wet AMD at any time, you should get an Amsler grid from your ophthalmologist. Use the grid every day to evaluate your vision for signs of wet AMD. This quick test works best for people who still have good central vision. Check each eye separately. Cover one eye and look at the grid. Then cover your other eye and look at the grid. If you detect any changes in the appearance of this grid or in your everyday vision while reading the newspaper or watching television, get a comprehensive dilated eye exam.If you have wet AMD and your doctor advises treatment, do not wait. After any treatment, you will need frequent eye exams to detect any recurrence of leaking blood vessels. Studies show that people who smoke have a greater risk of recurrence than those who don't. In addition, check your vision at home with the Amsler grid. If you detect any changes, schedule an eye exam immediately.