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Macular Degeneration: Causes, Symptoms, and Treatment
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Macular degeneration is not one disease, but a group of conditions that all cause the loss of centralized vision as the macula (the center bundle of photoreceptive nerve cells in the retina) is damaged over time. Changes to the middle of your vision, like fuzziness, distortions in straight lines or shapes, and a loss of central vision, all indicate late-stage macular degeneration, regardless of type.
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This condition is mostly associated with age. Those 65 years old are the most likely to begin developing the disease. There are, however, rare cases in which younger individuals can develop a type of macular degeneration. For the most part, factors like genetics, family history, gender, and eye hue are all associated with an increased risk of macular degeneration, and these cannot be controlled; however, lifestyle factors like diet, exercise, and smoking, are also associated with an increased risk, so you can make healthier choices to reduce your risk of macular degeneration if you are concerned.
The most important thing you can do is get regular eye exams because early and intermediate stages of macular degeneration will not have many symptoms associated with them, but an optometrist can spot changes inside your eye before you notice a visual difference. Getting an early diagnosis means you can get early treatment and consistent monitoring, which slows the progress of the disease and greatly reduces your risk of losing your sight.
What Is Macular Degeneration?
The term macular degeneration refers to a cluster of eye conditions, not just one disease, that affect the retina, leading to loss of central vision. Typically, macular degeneration affects people who are 65 or older, so macular degeneration is often denoted as 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.
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.
The retinal pigment epithelium (RPE) part in front of the macula provides metabolic support, removing old cells and debris from the photoreceptor cells so they can renew themselves. The choroid is a cluster of blood vessels behind the macula, which provides oxygen-rich blood and nutrients to the epithelium, and carries away waste products from the eye.
When everything in the eye functions properly, the macular remains healthy. Tissue deterioration is part of aging, however, and the beginning of macular degeneration occurs as the epithelium is less able to remove detritus from the area around the macula. This leads to clumps of yellowish cells that accumulate beneath the RPE, which are visible during an eye exam as small yellow dots called drusen. These collect beneath the retina, creating problem areas for visual acuity.
As the drusen continue to accumulate, RPE cells die, leading to bare spots called geographic atrophy. This prevents photoreceptor cells from functioning well, and the vision around the retina is lost. Patches of atrophied and dead cells can involve the center of the macula, called the fovea, leading to lost central vision. This may start as blurry or distorted vision, or a darkened area in the center of your visual field.
After the macula begins to be damaged to atrophied cells, new blood vessels from the choroid grow around the area in an attempt to bring more nutrients. This may be similar to getting a scar after an injury, when the body tries to heal itself. Unfortunately, when blood vessels grow in this area, it can make vision loss worse. However, the invasive growth of blood vessels into the area is rare. Only about 10 percent of people with macular degeneration experience this.
As this gets worse, without treatment, it can lead to legal blindness. In fact, macular degeneration is the most common cause of legal blindness in the United States, causing more problems than even cataracts. About 2.5 million people in the U.S. have macular degeneration, making daily activities like reading, driving, or seeing faces difficult. It is possible to have macular degeneration in one eye or to have a more severe form of it in one eye but a less severe form in the other.
Basic Symptoms Indicating 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 as well.
- 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, so it is important to get regular eye exams to slow the progress of this condition if you have it.
Types of Macular Degeneration
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’s 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’s disease affects the maculas of young children and adolescents, developing anywhere from ages 6 to 20. While it is the most common form of juvenile macular degeneration, it impacts only one out of every 20,000 adolescents in the U.S. It is linked to a genetic mutation in the ABCA4 gene, leading to protein abnormalities causing waste products to build up inside the RPE. 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’s 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:
- Family history. If your relatives, especially parents or siblings, have macular degeneration, you are more likely to develop this condition yourself.
- Late-stage AMD in one eye. While there is only about a 5 percent chance of developing late-stage macular degeneration if you receive a diagnosis of early-stage macular degeneration, having late-stage AMD in one eye increases your risk of developing late-stage AMD in the other eye.
- Smoking. Both smoking and being exposed to smoke can increase the risk of macular degeneration.
- Diet high in saturated fat. Regardless of your body composition, if you eat a lot of saturated fats, your risk of macular degeneration increases.
- Obesity. Being obese increases the risk of intermediate macular degeneration and the likelihood that the disease will progress faster.
- Cardiovascular disease. This impacts how blood flows around the body, which can lead to some cellular degeneration, including in the eyes, due to trouble removing waste products and getting enough oxygen to parts of the body.
- If you have chronically high levels of inflammation in your body, such as from an autoimmune condition, you are at greater risk for developing AMD.
- Being female. Women are more likely than men to develop AMD; however, this may be associated with age, since women live longer than men, and not specifically related to gender.
- Long-term UV exposure. Being outside in bright, direct sunlight very often, without the protection of UV-protecting sunglasses, increases your risk of several degenerative eye diseases, including AMD.
- Light-colored eyes. A lighter color in the iris has been linked to an increased risk of developing AMD.
- Caucasian: Being Caucasian has been associated with a higher risk of AMD.
- Farsightedness: Being farsighted for much of your life has been linked to an increased risk of AMD.
While several of these risk factors cannot be controlled, like gender 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.
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 get 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, and 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.
Treatment for Macular Degeneration (& Diagnosing)
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. These include:
- 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 at home, daily, if you have AMD at an intermediate or late stage, to determine if there have been any changes in your vision both eyes.
- 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.
Lifestyle changes recommended by doctors to slow AMD’s progress include:
- Taking vitamin supplements, especially lutein, zeaxanthin, vitamin C, vitamin E, and zinc.
- Eating more vegetables, especially leafy greens.
- Exercising regularly.
- Wearing UV-protective sunglasses outside.
- Quitting smoking.
Wet AMD medical treatments include:
- 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.
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. These include:
- Laser surgery, which works on a small segment of the population with wet AMD.
- Photodynamic therapy, in which 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.
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.
Frequently Asked Questions
What is the main cause of MD?
The primary cause of macular degeneration is damage to the macula of the retina because of aging. Advanced age, especially above 50 years of age, is the strongest predictor of macular degeneration.
How long does it take to lose vision with MD?
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.
What does a person see with MD?
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 whereby straight lines or shapes appear distorted.
Do you always go blind with MD?
Not every person with early MD 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
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- What is Macular Degeneration? (August 1, 2018). Everyday Health.
- Age-Related Macular Degeneration. American Optometric Association (AOA).
- Dry Macular Degeneration: Overview. (November 6, 2018). Mayo Clinic.
- Wet Macular Degeneration: Overview. (December 24, 2015). Mayo Clinic.
- How Is AMD Diagnosed and Treated? (May 17, 2018). American Academy of Ophthalmology (AAO).
- Have AMD? Save Your Sight with an Amsler Grid. (May 25, 2016). American Academy of Ophthalmology (AAO).
- Fluorescein Angiography. (January 20, 2016). Healthline.
- What Is Optical Coherence Tomography? (April 27, 2018). American Academy of Ophthalmology (AAO).
- Learn About Age-Related Macular Degeneration. (July 18, 2018). Centers for Disease Control and Prevention (CDC).
- What Is Avastin (Bevacizumab)? (June 1, 2015). Everyday Health.
- What Is Ranibizumab Ophthalmic? (November 11, 2018). Everyday Health.
- What Is Aflibercept Ophthalmic? (November 11, 2018). Everyday Health.
- Macular Degeneration Guide. American Foundation for the Blind (AFB).
- Dry Macular Degeneration: Diagnosis. (November 6, 2018). Mayo Clinic.
- Genetics of Age-Related Macular Degeneration: Current Concepts, Future Directions. (May 2011). Seminars in Ophthalmology.
- Macular Degeneration: Timeline of Vision Loss Progression. (March 2021). Very Well Health.
- 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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