Age-related macular degeneration, or AMD, is the leading cause for blindness in Americans over 55.
When you take off your glasses or remove your contact lenses, the world becomes blurry.
However, for people with age-related macular degeneration, the blurriness is present only at the center of the field of vision. The edges remain in focus. Objects in the central field may also be unusually bright or dark, appear distorted, or even become lost in a blank spot. Because of reduction in central field vision, detail-oriented tasks become more difficult over time.
In fact, the progression of vision loss is gradual and can be difficult to perceive over time.
That is why it’s critical to be examined by an optometrist or ophthalmologist at the very first sign of blurriness in the central field of vision. By the time these changes appear, AMD has already been progressing for some time and requires immediate treatment.
Here are four facts about this condition and its treatment.
1. AMD is the leading cause for blindness in seniors.
In developed countries, such as the United States, AMD is the most common cause for vision loss in people over age 50. The disease most commonly presents after age 60. Ten million Americans are currently diagnosed with AMD.
Nine out of 10 cases of AMD are of the dry type. Dry AMD can progress into wet AMD, which is more severe and accounts for about ten percent of AMD cases.
In the dry type, the presence of drusen (yellow protein and fat deposits beneath the retina) can degrade the viability of the photoreceptors in the macula—the most sensitive area of the retina, located at the back of the eye. The photoreceptor cells are what provide the electrical signals to the brain that result in sharp images.
When untreated, blood vessels grow under the macula and leak blood and other fluid into the macula, further degrading the viability of photoreceptor cells. The growth of these blood vessels marks the progression into wet AMD.
2. A dilated eye exam from a licensed optometrist or ophthalmologist is necessary to detect the disease.
A yearly eye exam is the best way to catch AMD. The disease can already be in its intermediate stages before people notice the central field loss on their own. While other primary care visits and school vision screenings can catch some eye problems, only optometrists and ophthalmologists dilate the eyes and perform the specific tests that can diagnose AMD. They are looking for the presence of drusen in the retina, blood vessels, and degradation of the macula.
Other tests that may be done while the eyes are dilated are a fluorescein angiogram and an optical coherence tomography scan.
Looking at an Ansler grid for potential distortions of the grid’s straight lines is another common way to help identify AMD.
3. Both genetic and lifestyle factors are thought to be at play in developing AMD.
Ongoing research is identifying more genes at play, but it is not thought that there is any one particular gene that by itself determines whether a person will develop AMD.
Although the causes of AMD are not known, there are several risk factors, with genetics playing a significant role. Age, race, and family history influence risk: Caucasians over age 60 with a family history of macular degeneration are statistically more at risk. Lifestyle contributors include smoking, poor diet, high sunlight exposure, and the presence of heart disease and high blood pressure.
Recent research has identified a suite of genes that contribute to risk. One gene in particular, Complement Factor H, is thought to be involved in more than half of AMD cases. Genes linked to hypersensitivity of the innate immune system also seem to be involved in AMD. For information on some of the latest genomic research, visit the Foundation Fighting Blindness.
4. AMD is a progressive disease, but visual therapy, new drugs, and even implants can help preserve vision.
As with any disease, prevention is the first approach recommended. According to the National Institutes of Health, “AMD occurs less often in people who exercise, avoid smoking, and eat nutritious foods including green leafy vegetables and fish. If you already have AMD, adopting some of these habits may help you keep your vision longer.”
Vision therapy is increasingly an option for those at later stages of the disease. Occupational therapists can offer adaptive devices specific to low vision, as well as strategies for daily independent living. Recent studies suggest that certain high-dose vitamin and mineral supplements may slow the advance of the disease.
Injections are a common treatment for the later stages of macular degeneration. The injections target the abnormal growth of blood vessels at the back of the eye, so that there is less fluid leakage into the eye.
Photodynamic therapy uses lasers to close off blood vessels in combination with a drug injected into the eye.
Similarly, laser surgery is also an end-stage treatment option, as is a new vision-enhancing implantable telescope that improves the resolution of central field vision.