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Macular Degeneration - What do I need to know?
What is AMD, Age-Related Macular Degeneration?
AMD is a leading cause of blindness for Americans over the age of 50. There are greater than 11 million people in the United States who have AMD. It affects a person’s central vision, which can make activities such as driving, reading and recognizing faces difficult.
What causes AMD?
AMD affects the tissue that lines the back of the eye called the retina. The central portion of the retina is called the macula. The macula is the portion of the retina that is responsible for our sharpest vision. At this point, no one knows the exact cause of AMD. It is thought to be a combination of heredity and environmental factors such as smoking and diet.
There are 2 types of AMD, dry and wet...What’s the difference?
Dry AMD is the first stage of the disease. It results from aging and thinning of the retinal tissue in the macular region and the deposition of pigment in this region. Ultimately, yellowish spots called drusen will accumulate. These spots are thought to be deposits or debris from the deteriorating tissue. Approximately 85-90% of patients with AMD have the dry form of the disease.
Typically, central vision loss with dry AMD is gradual and not as severe as wet AMD. However, this process of macular thinning can progress to a loss of retinal tissue, atrophy. The atrophy will present in patches that can grow and coalesce overtime, resulting in what is called late-stage geographic atrophy, GA. This can produce is severe vision loss.
Wet AMD occurs in approximately 10-15% of patients with macular degeneration. In these situations, dry AMD progresses to this more advances and damaging form of AMD. With wet AMD, new blood vessels grow beneath the retina, because of this wet AMD is sometimes referred to as neovascular AMD.
The process that causes wet AMD is the body’s attempt to grow new blood vessels to supply more nutrients and oxygen to the deteriorating retina tissue. These new blood vessels are frailer than the normal blood vessels within the eye. They will bleed and leak fluid. This process leads to scarring to the retina, resulting in blind spots in one’s central vision.
Risk factors for AMD include the following.
• Family history of AMD
• Aging – those over 60 years old
• Race – Caucasians have a higher rate of AMD
• Sex – females have a higher rate of AMD, possibly because they tend to live longer
• Light colored eyes
• Heart disease
• High blood pressure
• High cholesterol
• High sun exposure
• Poor diet – with low intake of anti-oxidants
What are symptoms of AMD?
• Difficulty seeing with central vision, which is needed for driving, reading, sewing and recognizing faces
• Trouble seeing in dim light
• Straight lines, such as window blinds, appear wavy, blurry or missing
• Fading and/or changes in the appearance of colors
There may be few if any symptoms early in the disease process, especially if one eye is minimally affected.
How is AMD diagnosed?
Yearly dilated eye exams are the key to diagnosing AMD. Early diagnosis is important in minimizing the risk for significant vision loss from AMD. It is important to adhere to this routine of yearly, dilated eye exams even if one has no noticeable vision problems.
If signs of AMD are noted on dilated eye exam, testing such as optical coherence tomography (OCT) is important to manage the disease. OCT testing provides a cross sectional image of the retinal tissue and the tissue below it called the choroid. Thickened tissue and fluid leakage is better examined with this type of testing. Retinal photography such as fluorescein angiography and autofluorescence imaging also allow better examination of retinal vasculature and atrophy.
How is AMD treated?
Currently, there are no FDA-approved treatments available for dry AMD. There are therapies in various stages of clinical trials. Two large, five-year clinical trials, the Age-Related Eye Disease Study (AREDS) in 2001 and a follow-up study called AREDS2 in 2013, have shown that nutritional supplements containing antioxidants and multivitamins as well as lutein and zeaxanthin can reduce the risk of dry AMD progressing to sight-threatening wet AMD. Neither of these studies showed a benefit of nutritional supplements in preventing the development of dry AMD in healthy eyes. To date, the best way to protect your eyes from developing AMD is to eat a healthy diet, exercise, wear sunglasses and don’t smoke. To summarize, a healthy lifestyle and proper nutrition can slow progression or minimize the risk of developing AMD, but they do not cure AMD.
The treatment of wet AMD has greatly changed over the last 20 years. Initially, there was no treatment at all. Then photodynamic therapy (PDT) emerged as a treatment option at the turn of the century. This treatment has since taken a back seat to anti-vascular endothelial growth factor (anti-VEGF) drugs, which are currently the standard treatment for wet AMD. These drugs block the development of new blood vessels and limit the leakage from abnormal blood vessels within the eye. They are administered via an injection into the eye. There is minimal discomfort experienced by the patient. Several injections over time are needed with this treatment.
What can be done for to address the vision loss associated with AMD?
The first step is a comprehensive eye exam. During this exam it will be determined if traditional eyeglasses will improve a patient’s vision. If traditional eyeglasses are not able to improve a patient’s vision to an appropriate level, the next step is a consultation with a low vision specialist, an eye doctor who specializes in providing visual aids for patients with vision loss from various conditions. These visual aids include, but are not limited to the following.
• Magnifying glasses, screens and stands
• Telescopic lenses
• High-intensity reading lamps
• Large print newspapers, magazines and books
• Close-circuit TVs that magnify a printed page onto a screen
• Computers and tablets