What is Age-Related Macular Degeneration?
Age-related macular degeneration (AMD) is a common eye condition and a leading cause of vision loss among people age 50 and older. More than 8 million people in the United States have AMD. It causes damage to the macula, a small spot near the center of the retina and the part of the eye needed for sharp central vision, which lets us see objects that are straight ahead.
In some people, AMD advances so slowly that vision loss does not occur for a long time. In others, the disease progresses faster and may lead to a loss of vision in one or both eyes. As AMD progresses, a blurred area near the center of vision is a common symptom. Over time, the blurred area may grow larger or you may develop blank spots in your central vision. Objects also may not appear to be as bright as they used to be.
AMD by itself does not lead to complete blindness, with no ability to see. However, the loss of central vision in AMD can interfere with simple everyday activities, such as the ability to see faces, drive, read, write, or do close work, such as cooking or fixing things around the house.
The macula makes up only a small part of the retina, yet it is much more sensitive to detail than the rest of the retina (called the peripheral retina). The macula is what allows you to thread a needle, read small print, and read street signs. The peripheral retina gives you side (or peripheral) vision. If someone is standing off to one side of your vision, your peripheral retina helps you know that person is there by allowing you to see their general shape.
- Researchers have found links between AMD and some lifestyle choices, such as smoking. You might be able to reduce your risk of AMD or slow its progression by making these healthy choices:
- Avoid smoking
- Exercise regularly
- Maintain normal blood pressure and cholesterol levels
- Eat a healthy diet rich in dark green, leafy vegetables and oily fish
Types of Age Related Macular Degeneration
There are two main types of age-related macular degeneration, wet and dry.
Dry Age-Related Macular Degeneration (AMD)
Most people who have macular degeneration have the dry form. Dry AMD is a condition commonly associated with aging. Drusen, which are yellow spots under the retina, are a hallmark of AMD. As a result of AMD, the macula may become thinner and stop working properly limiting a person’s central vision.
With dry macular degeneration, the vision loss is usually gradual. People who develop dry macular degeneration must carefully and constantly monitor their central vision, as the more damaging form of macular degeneration called wet (exudative) macular degeneration can develop.
Wet Age-Related Macular Degeneration
Wet macular degeneration occurs when abnormal blood vessels begin to grow underneath the retina. This blood vessel growth is called choroidal neovascularization (CNV) because these vessels grow from the vascular layer under the retina called the choroid. These new blood vessels may leak fluid or blood, blurring or distorting central vision. Vision loss from this form of macular degeneration may be faster and more noticeable than that from dry macular degeneration.
The longer these abnormal vessels leak or grow, the more risk you have of losing more of your detailed or central vision. Also, if abnormal blood vessel growth happens in one eye, there is an increased risk that wet AMD will occur in the other eye. The earlier that wet macular degeneration is diagnosed and treated, the better chance you have of preserving some or much of your central vision. That is why it is so important that you and your eye care professional monitor your vision in each eye carefully.
Treatment of Age-Related Macular Degeneration
While there is presently no medication or treatment for dry macular degeneration, a large scientific study has shown that antioxidant vitamins and zinc may reduce the impact of macular degeneration in some people by slowing its progression toward more advanced stages.
Wet AMD typically results in severe vision loss. However, retinal specialists can try different therapies to stop further vision loss. You should remember that the therapies described below are not a cure. The condition may progress even with treatment.
Injections. The number one option to slow the progression of neovascular AMD is to inject drugs into the eye. With neovascular AMD, abnormally high levels of vascular endothelial growth factor (VEGF) are secreted in your eyes. VEGF is a protein that promotes the growth of new abnormal blood vessels. Anti-VEGF injection therapy blocks this growth. If you get this treatment, you may need multiple monthly injections. Before each injection, your eye will be numbed and cleaned with antiseptics. Three different anti-VEGF drugs are available. They vary in cost and in how often they need to be injected, so you may wish to discuss these issues with your retinal specialist.
Photodynamic therapy. This technique involves “cold” laser treatment of the macula. First, a drug called verteporfin will be injected into a vein in your arm. The drug travels through the blood vessels in your body, and is absorbed by new, growing blood vessels under the retina. Your retinal specialist then shines a laser beam into your eye to activate the drug in the new abnormal blood vessels, while sparing normal ones. Once activated, the drug closes off the new blood vessels, slows their growth, and slows the rate of vision loss. This procedure is less common than anti-VEGF injections, and may be used in combination with them for specific types of neovascular AMD.
Laser surgery. Retinal specialists treat certain cases of neovascular AMD with laser surgery, though this is less common than other treatments. It involves aiming an intense “hot” laser at the abnormal blood vessels in your eyes to destroy them. This laser is not the same one used in photodynamic therapy that is referred to as a “cold” laser. This treatment is more likely to be used when blood vessel growth is limited to a defined area in your retina, away from the center of the macula, which can be easily targeted with the laser. Even so, laser treatment also may destroy some surrounding healthy tissue. This often results in a small blind spot where the laser has scarred the retina. In some cases, vision immediately after the surgery may be worse than it was before. But the surgery may also help prevent more severe vision loss from occurring years later.