What Causes Macular Degeneration?

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Medically reviewed by Christine L. Larsen, MD

Macular degeneration, also known as age-related macular degeneration (AMD), is the most common form of vision loss in older adults. It occurs when light-sensitive cells in the central part of the retina (the nervous tissue lining the back of the eye), or macula, die. This occurs either as a result of aging or due to abnormal blood vessel growth in tissues behind the macula. Depending on the cause, the changes in vision can either be very gradual—taking years—or rapid, happening within weeks.

Macular degeneration affects what you see and focus on straight ahead, worsening over time but rarely causing complete blindness. Common signs include blurry patches, waviness, a reduction in colors, and visual distortions.

Aging 

Macular degeneration occurs as cells within the retinal pigment epithelium (RPE) degrade and die. The RPE is a layer of light-sensitive cells in the macula, which is a small part of your eye’s retina. This cell degradation is caused by changes in the eye that occur due to aging.

With the more common form of this condition, “dry AMD,” the vision loss is more gradual. This type occurs as protein deposits, called drusen, develop behind the RPE. These grow and trigger an immune reaction, which impacts the cells in the macula, causing them to die. This eventually leads to a thinner RPE and eventually geographic atrophy: regions of dead cells.

Though more work is needed, researchers have linked macular degeneration to aging-related changes in the cells within the RPE. Known contributors to this condition include immune system activity, chemical imbalances, apoptosis (programmed cell death), and various environmental factors.

Abnormal Blood Vessel Growth

A more severe form of macular degeneration, neovascular or wet AMD, sets on much more rapidly and can lead to complete central vision blindness. With this type, abnormal blood vessel develop behind the macula, often due to an overproduction of vascular endothelial growth factor (VEGF). VEGF is a protein that plays a crucial role in angiogenesis, which is the formation of new blood vessels from existing ones.

If your body is overproducing VEGF, the blood vessels behind your macular can leak fluid and blood into the retina during angiogenesis, causing lesions (damaged areas) to form.

About one in 10 of those with dry AMD develop the wet type, which, representing about 10% of all macular degeneration cases. Like dry AMD, this type doesn’t affect peripheral vision. But it is more likely to progress to complete loss of central vision—accounting for 80% of such macular degeneration that doesn’t affect peripheral vision.

Is Macular Degeneration Hereditary? 

Genetics is among the factors associated with macular degeneration; however, it doesn’t have a clear pattern of inheritance. Up to 20% (one in five) of those with macular degeneration have a sibling or parent with the condition.

In evaluating data from 17,100 people with advanced macular degeneration, genetic researchers linked at least 19 genes to an increased risk of developing macular degeneration. Among these is the CFH gene, which is involved with the function of your immune system, as well as those involved with breaking down high density lipid (HDL) or “good” cholesterol.

Who Gets Macular Degeneration? 

While everyone is susceptible to macular degeneration, some people are more likely to develop it:

• Age: The older you are, the higher the risk. Among those older than 60, macular degeneration is the leading cause of vision loss, and rates rise with age.
• Biological sex: Though the evidence is limited, some studies have found higher rates of the condition among people assigned female at birth compared to people assigned males at birth.
• Race/ethnicity: Non-Hispanic white people have the highest rates of macular degeneration, followed by Hispanic people, African Americans, and Asian Americans. 

Risk Factors 

A wide range of diseases and health factors can raise your risk of developing macular degeneration and increase your chances that it progresses to an advanced form.

Smoking

Smoking tobacco and/or regular exposure to tobacco smoke is a significant risk factor for macular degeneration. Studies have found the chances of developing macular degeneration is twice as high in people who smoke compared to people who don’t smoke.

Having Obesity 

Obesity is defined as a body mass index (BMI) of 30, indicating that 30% of your weight is body fat. While some excess weight (overweight) wasn’t linked with macular degeneration, having obesity, and particular having a larger waist circumstance, raises the chances that your case will become more advanced and severe.

High Blood Pressure

Having hypertension, or high blood pressure, raises your risk of developing advanced or wet macular degeneration. This also raises your risk of cardiovascular diseases, such as coronary artery disease or heart failure, and has an inverse relationship with obesity, smoking, and sedentary lifestyle.

Cardiovascular Disease

Problems with heart and blood vessel health have also been linked with macular degeneration. In particular, researchers have found atherosclerosis—a thickening and hardening of blood vessel walls and the development of plaque in your arteries—to increase the chances of developing this condition.

Macular Degeneration in the Other Eye

Generally, macular develops in one eye at a time. But if you have macular degeneration in one eye, the chances that it forms in the other rises significantly.

Dietary Factors

A number of dietary factors may raise your risk. Foods high in fat, dairy, and high-glycemic foods (foods that raise your blood sugar), such as white bread, white rice, processed foods, cookies, and other baked goods, can raise your risk of macular degeneration and can cause it to advance more rapidly.

Conversely, foods high in antioxidants, such as berries, legumes, and nuts, may be able to help slow disease progression. However, more research is needed to examine the connection between diet and AMD.

Sedentary Lifestyle

Since it’s linked with cardiovascular disease, obesity, and high blood pressure, insufficient physical activity or sedentary lifestyle can cause macular degeneration to progress more rapidly. When you don’t get enough exercise, free radicals (unstable molecules that can damage your cells) are more likely to build up in your body and cause excess inflammation. Over time, this can lead to blood vessel damage that contributes to AMD.

A Quick Review 

Macular degeneration, also known as age-related macular degeneration (AMD), is one of the most common causes of vision loss in older adults. It occurs as light-sensitive cells in the macula—the central part of the retina—atrophy and die due to changes in the eye caused by aging. As a result, it affects your ability to see in front of you, causing blurriness, wavy lines, and eventually blind spots.

While all people are susceptible to developing macular degeneration, older adults are at an increased risk. Genetics and other health factors, like smoking and high blood pressure, have also been linked with this condition.

Read the original article on Health.com.