Age-related macular degeneration (AMD) is a disease that blurs the sharp, central vision you need for "straight-ahead" activities such as reading, sewing, and driving. AMD affects the macula, the part of the eye that allows you to see fine detail. 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 50 years of age and older.
There are two types of AMD: wet and dry.
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 considered to be advanced AMD and is more severe than the dry form.
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.
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 in the affected eye can be lost gradually.
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. 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.
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, see an eye care professional for a comprehensive dilated eye exam.
AMD can occur during middle age, but the risk increases with aging. Other risk factors include:
- 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 - People with a family history of AMD are at higher risk of getting the disease
- Gender - Women appear to be at greater risk than men
AMD is detected during a comprehensive eye exam that includes:
- Visual acuity test. This eye chart test measures how well you see at various distances.
- Dilated eye exam. Drops are placed in your eyes to widen, or dilate, the pupils. Your eye care professional uses a special magnifying lens to examine your retina and optic nerve for signs of AMD and other eye problems. After the exam, your close-up vision may remain blurred for several hours.
- Tonometry. An instrument measures the pressure inside the eye. Numbing drops may be applied to your eye for this test.
During an eye exam, you may be asked to look at an Amsler grid. The pattern of the grid resembles a checkerboard. You will cover one eye and stare at a black dot in the center of the grid. While staring at the dot, you may notice that the straight lines in the pattern appear wavy. You may notice that some of the lines are missing. These may be signs of AMD.
If your eye care professional believes you need treatment for wet AMD, he or she may suggest a fluorescein angiogram. In this test, a special dye is injected into your arm. Pictures are taken as the dye passes through the blood vessels in your retina. The test allows your eye care professional to identify any leaking blood vessels and recommend treatment.
When dry AMD reaches the advanced stage, no form of treatment can prevent vision loss. However, treatment can delay and possibly prevent intermediate AMD from progressing to the advanced stage, in which vision loss occurs. Slowing AMD's progression from the intermediate stage to the advanced stage will save the vision of many people.
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. Each treatment may slow the rate of vision decline or stop further vision loss, but 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. However, laser treatment also may destroy some surrounding healthy tissue and some 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.
- 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.
- Injections. Wet AMD can now be treated with a new drug that is 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 factor.
Want to prevent or slow vision loss? According to many eye care professionals, the best way to accomplish this is with early detection through regular eye exams.
Even though your vision may be clear, exams can uncover changes in the eye caused by high blood pressure, diabetes, eye tumors, retinal disorders and glaucoma. Some of these have no symptoms in the early stages. Eye exams can also lead to the earliest detection of other serious health problems-including diabetes or hypertension.
Also, children should have their first eye exam before entering kindergarten.
Schedule your eye exam today!