Age related vision loss
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. Though it doesn’t cause pain, AMD affects the macula, the part of the retina that 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 vision loss in Americans 60 years of age and older.
AMD occurs in two forms: 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. Damage to the macula occurs rapidly. With wet AMD, loss of central vision can occur quickly. An early symptom of wet AMD is that straight lines appear wavy or a dark spot appears in the center of the vision. 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 or gray 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 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 – yellow deposits under the retina often found in people over age 60.
Dry macular degeneration can sometimes lead to significant vision loss, but milder visual symptoms are more likely. More severe vision loss is usually due to wet macular degeneration. That’s why the wet form is considered more serious. Still, even with wet macular degeneration, complete vision loss is very unlikely. Patients who lose central vision may be unable to drive, read and perform other tasks that require sharp vision, but they almost always maintain peripheral vision. This usually allows them to walk around without assistance and perform other activities that do not require sharp central vision. Sometimes low vision aids will be helpful in some patients with more advanced AMD.
Treatment of Wet AMD
At the Irwin Retina Center, we offer several treatments for wet AMD, including:
Thermal Laser Treatment.
This procedure uses a laser to destroy the fragile, leaky blood vessels associated with wet AMD. A high-energy beam of light is aimed directly onto the new blood vessels and destroys them, preventing further loss of vision. However, there are limitations to the laser treatment. On average, treated patients experienced less vision loss than untreated patients – but they still lost some vision. And while laser treatment wipes out the abnormal blood vessel growth, it also damages the normal retina in that spot. Wherever the laser treatment is applied, the patient is left with a blind spot. The size and location of this blind spot will vary with where the abnormal blood vessels were. If the abnormal blood vessels were small, and not too close to the macular center, there may only be a small blind spot that the patient does not even notice. However, it is much more common for the abnormal blood vessels to be large and close to the center of the macula. Laser treatment then results in a noticeable blind spot. Still, this blind spot is often not as bad as the vision damage from the untreated blood vessels.
In this treatment procedure, the doctor injects a drug called Visudyne into the arm and activates the drug as it passes through the abnormal blood vessels by shining a low-energy laser beam into the eye. Visudyne is activated by the laser light, which produces a reaction that destroys abnormal blood vessels. The procedure is virtually painless. 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 more than once.
Wet AMD can be treated with drugs that are injected into the eye. The drugs that are used for this purpose are Macugen, Lucentis and Avastin. Macugen was the first drug injected in the eye for wet AMD. However, it has been replaced by newer drugs, i.e., Lucentis and Avastin. Macugen is administered via injections in the eye about every six weeks. In clinical trials, 33 percent of patients receiving Macugen maintained or improved their vision compared with only 22 percent in the control group. Macugen also helped slow the rate of vision loss for many age-related macular degeneration patients.
Approved by the FDA in June 2006 for treating wet macular degeneration, Lucentis (ranibizumab) is similar to the colorectal cancer treatment drug, Avastin. Lucentis works by inhibiting proteins called vascular endothelial growth factor (VEGF), which stimulate the growth of new blood vessels in the body. VEGF is thought to contribute to development of macular degeneration by promoting the growth of abnormal blood vessels in the retina. Lucentis clinical trial results leading to FDA approval were quite positive, especially when compared to outcomes of past-approved treatments. In late 2005, Genentech announced results of one study demonstrating improved or stable vision in about 95 percent of participants, compared with only about 60 percent of people receiving another treatment. Vision improvement with Lucentis was significant. While only 11 percent of the control group could see 20/40 or better following the study, about 40 percent of Lucentis patients were able to do so. Overall, about one-third of patients undergoing Lucentis treatment in FDA clinical trials experienced vision improvement.
Also known as an anti-VEGF drug as is Lucentis is used by many retinal specialists.
Most patients require an injection of Lucentis or Avastin on a monthly basis until the wet AMD is under control and there is no evidence of abnormal blood vessels or leakage in the macula. Although an injection in the eye sounds frightening, the retinal specialist prepares the eye for the injection in such a way that the injection is PAINLESS.
Retinal experts at the Irwin Retina Center are principal investigators in the CATT Study (Comparison of Age-Related Macular Degeneration Treatment Trials), which is evaluating Lucentis and Avastin for the treatment of wet AMD. Avastin is a drug closely related to Lucentis and has been widely used off-label in Europe, Canada and the United States to treat wet AMD for years. It was approved by the FDA in 2004 as a treatment for advanced colorectal cancer, but has shown considerable promise in treating patients with AMD. What’s more, Avastin is thought by some to remain in the eye longer than Lucentis, which could reduce the number of injections needed to treat the disease. Both therapies are manufactured by Genentech, Inc., but the cost of the two drugs varies widely. Lucentis costs roughly $2,000 per dose, while Avastin runs less than $100. Most patients with macular degeneration are covered by Medicare, so the federal government is very interested in findings that might reduce the cost of treatment. Besides evaluating whether Avastin is as good as or better than Lucentis, the CATT study also hopes to establish how much therapy a patient requires
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 AMD 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. Doctors at the Irwin Retina Center were instrumental in documenting this research. Presently there is an NIH-NEI sponsored AREDS II Clinical Trial being done at the Irwin Retina Center at Ingalls evaluating Omega-3 Fatty Acid, Lutein and Xanzanthin along with the original AREDS Formula to see how effective the treatment might be for dry AMD.