What is Age-Related Macular Degeneration?
What is Age-Related Macular Degeneration?
Age-related macular degeneration (AMD)—the leading cause of vision loss for people over 60—gradually destroys the central vision needed to see objects clearly and to perform common daily tasks. AMD affects the macula, the central part of the retina, which allows us to read, drive and recognize faces. Although AMD can lead to central or legal blindness, it causes no pain, and in some cases, advances so slowly that those affected notice little change in their vision. With other people, the disease progresses much faster and can lead to a loss of vision in both eyes. Those who have advanced AMD in one eye are at especially high risk of developing it in the other eye.
The chance of developing AMD is associated with inherited genes that direct cellular behavior. That likelihood is related to a combination of factors, including a person’s age and health, environmental exposures and genetic predisposition. Although there are several subcategories, AMD is typically diagnosed as being one of two varieties―dry or wet. Each type affects vision differently and is therefore treated and managed differently.
What is dry AMD?
Most cases of AMD originate in the dry form, which is characterized by the aging of the macular tissues. Byproducts of retinal metabolism collect under the retina in clumps known as drusen, which accumulate over time and interfere with the delivery of nutrients to the retina. The retina slowly begins to atrophy and sustain a varying amount of damage in response to the drusen. This condition typically results in mildly decreased vision, although some people do experience moderate or even severe visual loss with dry AMD.
How is dry AMD diagnosed?
Dry AMD is most often detected during a comprehensive exam by your eye care professional. After having your vision and eye pressure checked, drops are placed in your eyes to widen, or dilate, the pupils. Your retina specialist uses a special magnifying lens to examine the macula for signs of AMD (including drusen) and other eye problems. Additional tests are often performed that further evaluate findings detected on clinical examination. After the exam, your close-up vision may remain blurred for several hours after your eyes have been dilated.
How is dry AMD treated?
If your doctor notes signs of AMD during the exam, he or she is likely to recommend you start taking special vitamins. The Age-Related Eye Disease Study (AREDS) evaluated a specific combination of vitamin and mineral supplements found to reduce the likelihood of dry AMD progressing to wet AMD, and its risk of associated vision loss.
Recommendations for a specific AREDS vitamin formula have changed since the original study. While most patients currently take the AREDS 2 formula, that may change as the understanding of this disease evolves.
During an eye exam, you may be asked to look at an Amsler grid, with vertical and horizontal lines that resemble a checkerboard. Your doctor may ask you to check your vision daily with an Amsle r grid at home and report any changes immediately. It is always important for patients to monitor their own vision, especially those approaching or having already passed the age of 60, or those diagnosed with dry AMD.
It is critical to detect and alert your doctor of even the slightest vision change that could signal the transition from the dry to the wet form of the disease. If treated immediately, the onset of wet AMD can be stopped or slowed dramatically. Once wet AMD reaches the advanced stage, in many cases, vision cannot be improved.
Amsler Grid Directions For Use
(Under a good light source/wearing reading glasses, if any)
- Place chart 12 to 14 inches away on a flat surface.
- Wearing your reading glasses, cover left eye.
- Fix on center dot, looking at the grid with the right eye.
- Cover right eye and look at the grid with the left eye.
- See doctor as soon as possible if lines are wavy, blurred or missing.
What is wet AMD?
In addition to the comprehensive eye exam described earlier, your retina specialist will regularly perform a computerized scan of the retina (optical coherence tomography, or OCT Scan) to check for retinal leakage or swelling. During this brief and painless test, a low energy laser scans the retina and provides a cross-sectional evaluation of the macula.
Although only 10-15% of people with dry AMD progress to wet AMD, this form is far more serious and may cause severe visual loss. Wet macular degeneration begins when abnormal blood vessels grow under the macula near areas of drusen, where tissue has been eroded. These fragile vessels will leak fluid and blood, resulting in severe visual disturbances, sometimes in only a few days. Fortunately, there are multiple therapies available to treat the wet form of this devastating disease, with many more in development—thus making early detection all the more critical.
How is wet AMD diagnosed and monitored?
In addition to the comprehensive eye exam described above, your retina specialist may suggest a fluorescein angiogram if he or she has reason to suspect wet AMD may be developing. In this test, a special dye is injected into your arm and pictures are taken as the dye passes through the blood vessels in your retina. This allows your doctor to identify any leaking blood vessels and recommend immediate treatment if necessary. Your doctor may also recommend Ocular Coherence Tomography, or OCT, to check for AMD progression. This is a non-invasive test, similar to an ultrasound, that helps detect fluid within the macula. At RCPR we are also pleased to be able to offer the new diagnostic modality of OCT-Angiography, a new type of OCT imaging in which normal and abnormal retinal and choroidal vessels are visualized without injecting a dye.
How is wet AMD treated?
Wet AMD is currently treated with drugs that are injected directly into the vitreous cavity of the eye. The eye is numbed and treated with an antiseptic before each injection. The injection is made at the side of the eye, through the sclera (white structural wall of the eye).
Typical side effects are transient and include floaters, increased eye pressure, inflammation, broken blood vessel or eye pain. Serious side effects are rare, but can include infection, bleeding within the eye, retinal detachment and acute cataract. Multiple monthly injections are usually required to control wet AMD. Therapy may be adjusted once the condition is determined to be well controlled.
How do the injected drugs work?
Excessively high protein levels of vascular endothelial growth factor (VEGF) occur in eyes with wet AMD, which promotes the growth of abnormal new blood vessels and scar tissue beneath the retina. Fortunately, there are several newer drugs that bind to VEGF (anti-VEGF drugs) and serve to inhibit the damage caused by active wet AMD.
Multiple studies have compared these anti-VEGF drugs and they have been found to be equally effective in helping patients retain their vision, even though patients may differ in how the ir eyes respond to one treatment versus another . None of these, however, is a cure for the disease and vision loss may continue despite treatment, prompting your doctor to switch medications in hopes of improving results. While the drugs described below are the most common treatments for wet AMD, your doctor may recommend other therapies.
This drug was initially approved by the FDA for intravenous use in halting the progression of advanced colon cancer. Avastin is now the most commonly-used drug for treating wet AMD worldwide.
Lucentis was approved by the FDA in June of 2006 for the treatment of wet AMD. Large clinical trials showed that it slows the rate of vision loss from wet AMD and is comparable to Avastin in its effectiveness against wet AMD. In addition, over one-third of patients were found to experience significant improvement in vision.
This is the most recent FDA-approved drug for the treatment of wet AMD. Eylea has properties similar to Lucentis and Avastin in binding to VEGF. Its advantage is that, in most cases, it can be given less frequently than those other drugs, thus requiring fewer injections to the patient.
What other therapies exist for treating wet AMD?
In more advanced cases of wet AMD, drug therapy alone may not effectively control the disease. In these circumstances, your doctor may recommend additional treatments, including photodynamic therapy (PDT) (intravenous drug Visudyne® with laser) or surgery (including a clot-busting drug, TPA) to augment the use of medication.