What is age-related macular degeneration?
Age-related macular degeneration (AMD) is a disease associated with aging that gradually destroys 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 eye that allows you to see fine details. AMD causes no pain.
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 vision loss in Americans 60 years of age and older.
AMD occurs in two forms: wet and dry.
What is wet AMD?
Wet AMD occurs when abnormal blood vessels behind the retina 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 raise the macula from its normal place at the back of the eye. Damage to the macula occurs rapidly.
With wet AMD, loss of central vision can occur quickly. Wet AMD is also known as advanced AMD. It does not have stages like dry AMD.
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 at once. You need a comprehensive dilated eye exam.
What is dry AMD?
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 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 can be lost in one eye while the other eye seems unaffected.
One of the most common early signs of dry AMD is drusen.
What is drusen?
Drusen are yellow deposits under the retina. They often are found in people over age 60. Your eye care professional can detect drusen during a comprehensive dilated eye exam.
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:
- Early AMD. People with early AMD have either several small drusen or a few medium-sized drusen. At this stage, there are no symptoms and no vision loss.
- Intermediate AMD. People with intermediate AMD have either many medium-sized drusen or one or more large drusen. Some people see a blurred spot in the center of their vision. More light may be needed for reading and other tasks.
- Advanced Dry AMD. In addition to drusen, people with advanced dry AMD have a breakdown of light-sensitive cells and supporting tissue in the central retinal area. This breakdown can cause a blurred spot in the center of your vision. Over time, the blurred spot may get bigger and darker, taking more of your central vision. You may have difficulty reading or recognizing faces until they are very close to you.
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. If blurriness occurs in your vision, call Southern Eye Associates to schedule an appointment for a comprehensive dilated eye exam.
Ninety percent of all people with AMD have this type. Scientists are still not sure what causes dry AMD.
Which is more common-the dry form or the wet form?
Vision with Macular Degeneration
Same scene viewed by a person
with age-related macular degeneration.
The dry form is much more common. More than 85 percent of all people with intermediate and advanced AMD combined have the dry form.
However, if only advanced AMD is considered, about two-thirds of patients have the wet form. Because almost all vision loss comes from advanced AMD, the wet form leads the significantly more vision loss than the dry form.
Can the dry form turn into the wet form?
Yes. All people who have the wet form had the dry form first.
The dry form can advance and cause vision loss without turning into the wet form. The dry form also can suddenly turn into the wet form, even during early stage AMD. There is no way to tell if or when the dry form will turn into the wet form.
Who is at risk for AMD?
The greatest risk factor is age. Although AMD may occur during middle age, studies show that people over age 60 are clearly at greater risk than other age groups. For instance, a large study found that people in middle-age have about a 2 percent risk of getting AMD, but this risk increased to nearly 30 percent in those over age 75.
Other risk factors include:
- Smoking. Smoking may increase the risk of AMD.
- Obesity. Research studies suggest a link between obesity and the progression of early and intermediate stage AMD to advanced AMD.
- Race. Whites are much more likely to lose vision from AMD than African Americans.
- Family history. Those with immediate family members who have AMD are at a higher risk of developing the disease.
- Gender. Women appear to be at greater risk than men.
How is wet AMD treated?
Wet AMD can be treated with 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.
- Laser surgery. This procedure 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. Only a small percentage of people with wet AMD can be treated with laser surgery. Laser surgery is more effective if the leaky blood vessels have developed away from the fovea, the central part of the macula. (See illustration at the beginning of this document.) Laser surgery is performed in a doctor’s office or eye clinic.
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.
- 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 the 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 you skin or eyes to direct sunlight or bright indoor light for five days after treatment.
Photo dynamic 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.
- Injections. Wet AMD can now be treated with new drugs that are injected into the eye (anti-VEGF therapy). Abnormally high levels of a specific growth factor occur in eyes with wet AMD and promote the growth of abnormal new blood vessels. This drug treatment blocks the effects of the growth 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.
How is dry AMD treated?
Once dry AMD reaches the advanced stage, no form of treatment can prevent vision loss. However, treatment can delay and possibly prevent intermediate ADM from progressing to the advanced stage, in which vision loss occurs.
The National Eye Institute’s Age-Related Eye Disease Study (AREDS) 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.