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Macular Degeneration: Causes, Symptoms, and Treatment
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Macular degeneration (MD) is not one disease. It’s a group of conditions that all cause loss of centralized vision as the macula (the center bundle of photoreceptive nerve cells in the retina) is damaged over time.
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What Is Macular Degeneration?
Macular degeneration is the loss of tissue in the macula, which is part of the centralized back portion of the retina. This part of the eye is a large collection of photoreceptor cells, gathering light and sending information through the ocular nerve to the brain to be processed into images. The macula does much of the photo-processing work in the eye, and it is considered the most sensitive part of the retina.
As this gets worse, it can lead to legal blindness without treatment. In fact, macular degeneration is the most common cause of legal blindness in the United States, causing more problems than even cataracts.
Typically, macular degeneration affects people who are 65 or older, so macular degeneration is often called age-related macular degeneration (AMD). About 1 in 10 people older than 65 has a diagnosis of macular degeneration, and about 1 in 100 people suffer severe vision loss because of this eye condition.
Key Facts About Macular Degeneration
- Macular degeneration will likely advance without treatment and can result in complete vision loss. It’s the leading cause of legal blindness in the U.S.
- There are two common types of macular degeneration: wet AMD and dry AMD. Dry AMD is the most common form and characterized by a more gradual development of vision problems. Wet AMD is less common and usually involves a rapid onset of symptoms that can quickly lead to severe (or complete) vision loss if left untreated. Wet AMD is caused by the growth of abnormal blood vessels beneath the retina.
- Treatment options for dry AMD are limited and may include lifestyle changes and vitamins. Treatment options for wet AMD usually include eye injections known as anti-VEGF therapy. Anti-VEGF therapy slows the growth of the blood vessels that cause wet AMD.
Symptoms of Macular Degeneration
There are a few types of macular degeneration. They all have atrophying and cell death in the macula in common, so they all have some symptoms in common, such as these:
- Reduced or distorted vision
- Trouble differentiating colors
- A blurry area in the center of your vision
- A blind spot in the middle of your vision
- A spot that appears dark or “missing” in the middle of your vision
- General haziness in overall vision
- Shapes of objects appearing distorted
- Otherwise straight lines appearing distorted or wavy
These symptoms are not likely to begin until significant damage has been done to the macula. Your optometrist can spot the early stages of AMD before you even notice symptom development.
What Does Macular Degeneration Look Like?
There may be few visual signs of macular degeneration, and the symptoms of AMD may be similar to those of other eye problems, which is why it’s so important to get regular eye exams.
One visual symptom of macular degeneration is the presence of drusen. These are small yellow deposits under the retina that are a sign of the early stage of AMD. Still, drusen deposits are tiny and can only be seen during a professional eye exam.
Types of Macular Degeneration
| Type | Age of Onset | Prevalence | Cause | Symptoms | Unique Characteristics |
| Dry AMD | Older than 60 | 85-90% | Genetic, environmental | Wavy lines, distorted shapes, trouble recognizing faces, difficulty reading, especially in low light | Accumulation of drusen |
| Wet AMD | Generally follows dry AMD or can occur first | 10% | Progression from dry AMD | Rapid onset, well-defined blurry or blank spot in the center of vision, abnormal blood cell growth, fluid leakage affecting retinal function | Rapid onset, well-defined blurry or blank spot in the center of vision, abnormal blood cell growth, fluid leakage affecting retinal function |
| Stargardt Disease | 6 to 20 | Rare | Death of photoreceptor cells in the macula | Difficulty reading, trouble transitioning between light and dark rooms | Vitamin A can be toxic |
Most macular degeneration is caused by age, but there are different categories of AMD and other conditions that can impact the macula.
- Dry macular degeneration: This is the most common form of macular degeneration, occurring in 85 to 90 percent of cases of AMD. It is most likely to occur in people who are older than 60, and it has been linked to both genetic and environmental risks, like smoking.
Dry AMD involves the accumulation of drusen, but no vascular changes. Wavy lines, distorted shapes, trouble recognizing faces, and difficulty reading, especially in low light, are particularly associated with dry AMD.
- Wet macular degeneration: This condition involves the development of dry AMD first, with vascular growth and increasing blindness following. Abnormal blood cell growth can lead to blood or fluid leaking, which interferes with retinal functioning. Fluid may also leak from the choroid itself, collecting in the RPE, leading to a bump in the macular and causing vision problems.
About 10 percent of people with macular degeneration develop wet AMD, and it is possible, but rarer, for wet AMD to develop first, followed by dry AMD. Wet AMD is characterized most often by rapid onset of symptoms and a well-defined blurry or blank spot in the center of vision. - Stargardt disease: This is a rare form of macular degeneration caused by the death of photoreceptor cells in the macula. Unlike wet and dry macular degeneration, Stargardt disease affects the macula of young children and adolescents, developing anywhere from ages 6 to 20.
The first signs of the condition are difficulty reading and trouble going from light rooms to dark rooms. Also, unlike wet or dry AMD, vitamin A can be toxic to people with Stargardt disease because they do not metabolize it.
Risk Factors Associated With Macular Degeneration
Age is the most common risk factor for macular degeneration. About 0.2 percent of people in the U.S. between ages 55 and 64 have developed AMD; 1 percent of people 65 to 74 years old have AMD; 4.6 percent of people ages 75 to 84 have AMD: and 13.1 percent of people ages 85 and older have AMD.
Other risk factors that increase your chances of developing AMD include the following:
- Family history
- Late-stage AMD in one eye
- Smoking
- Diet high in saturated fat
- Obesity
- Cardiovascular disease
- Inflammation
- Female
- Long-term UV exposure
- Light-colored eyes
- Caucasian
- Farsightedness
While several of these risk factors cannot be controlled, like sex and age, some can be improved with lifestyle changes. Exercise regularly, eat a healthy diet full of vegetables, protect your eyes when you are outside, quit smoking, and talk to your doctor about any risks that may be associated with prescription drugs.
You may also want to speak to your optometrist if you have uncontrollable risk factors, like family history, and are concerned about your chances of developing AMD. This way, your optometrist will know to monitor your eyes for this condition in particular, which will allow for earlier diagnosis and treatment.
What Causes Macular Degeneration?
There isn’t a clear-cut cause of macular degeneration. A combination of environmental and genetic factors are believed to contribute to its formation. Macular degeneration generally worsens with age.
Stages of Macular Degeneration
There are three basic stages of AMD progression.
- Early: During this stage, you are not likely to experience any AMD symptoms, but your eye will begin to accumulate drusen, which are about the width of a human hair. These will be noticeable during a routine eye exam.
- Intermediate: As the drusen gets larger, the impact on your vision will become apparent. This may start as pigment changes to your retina or a little bit of vision loss. Your daily activities will not be greatly impacted by any changes you experience. The main way this stage is diagnosed is through a routine eye exam.
- Late: Large drusen in the macula will lead to noticeable loss of vision. However, if you have late-stage AMD in one eye, your other eye may compensate for a long time, so you may not notice until your vision is severely damaged.
Diagnosis of Macular Degeneration
Drusen will be noticeable during routine eye exams, so it is important to visit an optometrist every year. Your optometrist will dilate your pupils, allowing them to look at several parts of your eye and see if there are any abnormalities, changes, or damage.
If your optometrist finds drusen, they may run some other tests on your eyes.
- Amsler grid: This checks the center of your vision for defects with a series of straight lines. If you have macular degeneration, some of the lines in the grid will appear distorted, broken, or faded. This test can be used daily at home if you have AMD at an intermediate or late stage to determine if there have been any changes in your vision.
- Fluorescein angiography: Your doctor will inject a colored dye into a vein in your arm, which will travel to the blood vessels in your eyes and make them more visible to your optometrist. A special camera will take pictures of these vessels, allowing your optometrist to see if you have any abnormal growth around the retina. This test also tracks diabetic retinopathy.
- Optical coherence tomography (OCT): This is a noninvasive imaging test, creating detailed cross-sections of your retina’s layers, allowing your optometrist to spot places that are thicker, swelling, or thinning. This test will be used to diagnose AMD as well as follow the effectiveness of your treatment plan.
Treatment for MD
While there is no cure for macular degeneration, several treatments can slow the progression of the disease and reduce the risk of serious vision loss. Dry AMD treatments revolve around lifestyle changes, while wet AMD treatments involve prescription medications alongside lifestyle changes.
Lifestyle Changes
Lifestyle changes recommended by doctors to slow AMD’s progress include the following:
- Take vitamin supplements, especially lutein, zeaxanthin, vitamin C, vitamin E, and zinc.
- Eat more vegetables, especially leafy greens.
- Exercise regularly.
- Wear UV-protective sunglasses outside.
- Quit smoking.
Prescription Medications
Wet AMD medical treatments include the following:
- Avastin (bevacizumab): This medication was developed to stop the progression of cancerous tumors by slowing blood vessel growth. It is used off-label for wet AMD.
- Lucentis (ranibizumab): Created from a human antibody fragment, the ophthalmic version of this drug prevents blood vessels from forming under the retina and leaking into the macular area.
- Eylea (aflibercept): This medication is similar to Lucentis. Made from a human antibody fragment, it prevents the formation of blood vessels under the retina.
These prescription medications form anti-VEGF therapy. They are injected into your eye by your ophthalmologist about once a month, or every four weeks.
Surgical Options
People with advanced dry AMD may undergo surgery to implant a telescopic lens in one eye. This has a narrow field of view, but inserting this tiny plastic tube full of lenses will improve both up-close and distance vision.
There are some surgical options for people with wet AMD.
- Laser surgery: This works on a small segment of the population with wet AMD.
- Photodynamic therapy: For this therapy, a drug is injected into a vein, travels into the blood vessels around the eye, and, when activated by light, destroys newer blood vessels that have formed.
Long-Term Prognosis
With regular eye exams, your chances of suffering from serious, life-limiting macular degeneration are very low. While the condition is not reversible, making healthy life choices reduces your risk of developing the condition, and they can help slow the progression of the disease if you do develop it.
Medical treatments are constantly improving as well, making surgical treatment of AMD more viable.
Macular Degeneration FAQs
The primary cause of macular degeneration is damage to the macula of the retina because of aging. Advanced age, especially being older than 50, is the strongest predictor of macular degeneration.
Macular degeneration stages are characterized by the accumulation of the yellow deposits (drusen) in the macula. Vision loss often occurs when the condition progresses to the late stage where significant retinal damage has occurred.
One to three people out of 100 with small drusen experience vision loss within five years of diagnosis. About 50 percent of people with large drusen experience vision loss within five years. Generally, it takes approximately 10 years to progress from diagnosis to legal blindness. Someone with wet AMD may experience rapid vision loss within days if untreated.
A person with AMD may see blurry areas, blind spots, or dark spots in and around their central visual field. They may also have distorted vision where straight lines or shapes appear distorted.
Not every person with early macular degeneration will progress to the late-stage AMD. Macular degeneration by itself does not lead to complete blindness. Some peripheral vision remains in nearly all cases of AMD.
References
- What Causes Macular Degeneration in the Eyes? Have There Been Any Advances in Curing This Condition? (2018). Scientific American.
- Age-Related Macular Degeneration. American Optometric Association.
- Age-Related Macular Degeneration. National Library of Medicine.
- How Is AMD Diagnosed and Treated? (May 2018). American Academy of Ophthalmology.
- Have AMD? Save Your Sight with an Amsler Grid. (May 2016). American Academy of Ophthalmology.
- What Is Optical Coherence Tomography? (April 2018). American Academy of Ophthalmology.
- Learn About Age-Related Macular Degeneration. (July 2018). Centers for Disease Control and Prevention.
- Macular Degeneration Guide. American Foundation for the Blind.
- Genetics of Age-Related Macular Degeneration: Current Concepts, Future Directions. (May 2011). Seminars in Ophthalmology.
- Recognizing Age-Related Macular Degeneration in Primary Care. (March 2017). Journal of the American Academy of Physician Assistants.
- Ten-Year Follow-Up of Age-Related Macular Degeneration in the Age-Related Eye Disease Study: AREDS Report No.36. (March 2014). National Center for Biotechnology Information.
- Age-Related Macular Degeneration (AMD) Data and Statistics (July 2019). National Eye Institute.
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