What Is Macular Degeneration?

Particularly after age 50, many people have concerns about developing the potentially vision-damaging condition known as age-related macular degeneration (AMD).

AMD affects the central part of the light-sensitive retina at the back of the eye, the nerve tissue that sends visual information to the brain. This area, called the macula, is responsible for your ability to see fine details.

In cases in which AMD is advanced, damage to the macula occurs, causing those with this condition to have difficulty distinguishing faces or reading letters on a page. However, side vision usually remains intact.

This article will explain how to tell the difference between the two types of AMD (wet and dry), explain the symptoms of each, its causes, and how this condition is diagnosed and treated. It will also highlight what to know about progression and more.

Wet vs. Dry Macular Degeneration

Dry AMD and wet AMD are the two types of macular degeneration. They have significant differences.

Most people with AMD (about 80%) have dry macular degeneration, also called atrophic AMD. With this form, the macular tissue thins as you age, and yellowish fat and protein deposits known as drusen build up in the area. Dry AMD is the slower form of the disease. Vision loss may be mild in some cases and more significant in others.

In wet AMD, abnormal blood vessels develop in the eye. These can leak onto the retina, causing macular scarring. With this form, you may only realize you have wet AMD once you contend with vision issues like blurring. That's why having an eye doctor, such as an ophthalmologist or optometrist, regularly examine your eyes is crucial.

Macular Degeneration Symptoms

The visual symptoms you have with macular degeneration will depend upon the type. Here is what you can expect from each.

Dry Macular Degeneration Symptoms

With dry macular degeneration, the symptoms will depend on how far the condition has progressed. Early on, there may not even be any symptoms. The good news is that this dry form can take a long time to advance. When symptoms do appear, they may include:

• Slight blurriness and difficulty seeing in dim conditions

• Gaps or dark smudges, particularly in your central vision

• Colors may seem faded.

• Straight lines suddenly appear crooked or wavy.

Wet Macular Degeneration Symptoms

With wet macular degeneration, also known as exudative, the condition can occur suddenly, sometimes in days. Those with the dry form of macular degeneration may also go on to develop the wet form. Signs that you are contending with wet AMD include:

• Visual distortions, with wavy lines appearing in place of straight ones

• Blank spots appearing in the vision

• Loss of central vision

What Causes Macular Degeneration

AMD affects over 20 million Americans, with the risk increasing with age. Those age 75 and over face a 1 in 3 chance of developing AMD.

While scientists know a lot about the factors that can contribute to AMD and make people vulnerable to developing it, they have yet to pinpoint the cause. They do know that the macula begins to break down due to errors in the way the body functions.

Some risk factors can be modified, while others can't. Factors that contribute to the development of AMD include the following:

• Age

• Smoking
  

• Eating fat-filled food such as potato chips, french fries, peanut butter, and cookies

• Sun exposure without proper eye protection over a long period

• Uncontrolled high blood pressure

• Cardiovascular disease that's unregulated
  

• Being farsighted (seeing distant objects clearer than those up close)

• Having light-colored eyes

• Being female (although evidence is conflicting)

• Having obesity

• Having close family members with the condition
  

Is Macular Degeneration Hereditary?

While scientists haven't identified a specific gene with macular degeneration, they believe a genetic component exists. AMD tends to run in families.

Seven genetic regions appear to be associated with macular degeneration. However, these are not just on one chromosome. These are associated with different genetic areas, including those involved in immune system regulation, cellular structure maintenance, blood vessel permeability and growth, lipid metabolism, and plaque buildup on arteries.

The hope is that learning more about genetics regarding this condition will lead to the availability of new diagnostics and treatments.

Also, genetics has already been determined to factor into conditions such as Stargardt's disease, sometimes referred to as inherited macular degeneration or juvenile or early-onset AMD. At its core, Stargardt's disease involves mutations in the ABCA4 gene. This condition results in central vision loss and affects about 30,000 people.

Macular Degeneration Test: How to Diagnose AMD

While it's usually an ophthalmologist or optometrist who notices the telltale signs of AMD during an annual exam, it's possible to watch for signs of this condition on your own with the aid of an Amsler grid test.

The Amsler grid resembles a piece of graph paper with a dot in the center. The idea is to look for lines that appear missing, distorted, or wavy on a daily basis. You can report any changes to your ophthalmologist as soon as you detect them.

Other tests that you may need to undergo include the following:

• Optical coherence tomography: This noninvasive test takes about 15 minutes and uses infrared waves of light to develop cross-sectional images of the retina.

• Fundus fluorescein angiography: Using this test, which takes about 20 minutes, the ophthalmologist injects fluorescein dye into your arm and then takes sequential photographs of the eye to show blood flow or any vessel leakage.

• Fundus autofluorescence imaging: This technique looks for areas of the eye that tend to light up naturally when exposed to particular light wavelengths. The idea is to find those areas that should light up but don't due to damage from AMD.

• Genetic testing: Such testing can identify genes responsible for what's thought of as early-onset AMD, such as Stargardt's disease.

Macular Degeneration Treatment

Treatment may be what stands between you and vision loss. While you will likely never lose your peripheral vision with AMD, your central vision is at risk. With dry macular degeneration, such vision loss may take several years. But with the wet form, this may occur over a few months unless you promptly undergo treatment.

If you have the wet form, you can be treated with anti-vascular endothelial growth factor (anti-VEGF) injections. These can help to keep abnormal new blood vessels from developing. But the vision already lost may come back minimally or may not come back at all.

Another possible treatment is photodynamic therapy. With this, your ophthalmologist injects into your arm a light-sensitive medicine. This collects in abnormal blood vessels in the eye. Then they use a laser to seal any abnormal blood vessels in your retina.

There have been attempts at submacular surgery where the idea was to remove any abnormal blood vessels near the macula. But this has yet to prove very successful.

Unfortunately, if you have dry AMD, there is no treatment, but clinical trials are assessing treatments that may become available. You can learn to better use what vision you have with low-vision devices and vision rehab services.

A specific vitamin and mineral supplement called AREDS 2 formula, developed and tested in clinical studies, may help slow the progression of dry AMD. Talk to your healthcare provider to discuss whether this supplement is right for you.

How Dry AMD Progresses to Wet AMD

While dry AMD progresses much more slowly than wet AMD, the catch is that this condition can suddenly change into the wet form at any point. This occurs when new abnormal blood vessels grow under the macula, leak, and cause damage.

This conversion only happens in 10% to 15% of people. When it does, the switch to wet AMD usually occurs late in the condition.

These stages usually occur before it wet AMD is noted:

• Subclinical AMD occurs when the eye loses its ability to adapt to darkened conditions. But during this early stage, no telltale drusen deposits are found in the eye.

• Medium-sized drusen marks early AMD, which the eye doctor usually detects during a routine eye exam.

• Intermediate AMD involves larger drusen or retinal pigment abnormalities.

• Advanced AMD is the stage marked by central vision loss due to the death of photoreceptors. At this stage, you may develop the advanced form of dry macular degeneration known as geographic atrophy or progress to wet AMD.

What you do may impact whether your dry AMD progresses to the wet form. Lifestyle factors that may contribute here include eating foods high in saturated fat, being overweight, smoking, and having high blood pressure.

Can You Prevent Macular Degeneration?

If you implement lifestyle triggers linked to AMD, such as quitting or never starting smoking or lowering your cholesterol, you may be able to keep AMD at bay.

In addition to modifying your lifestyle, some studies indicate that taking supplements or eating foods high in vitamin C, vitamin E, beta-carotene, zinc, and copper can also help keep AMD from progressing to the later stages.

Protection from exposure to the ultraviolet (UV) rays of the sun is important to preserving eye health, including reducing damage leading to AMD. Limit exposure, especially from 10 a.m. to 4 p.m. Also, wear a wide-brimmed hat and ultraviolet-screening sunglasses. The best sunglasses are large and wrap around the sides of the face.

Living With Macular Degeneration

Unfortunately, once you lose vision due to AMD, it cannot be reversed. As soon as you are diagnosed with AMD and are having functional vision difficulties, you should be referred to a low-vision specialist for a low-vision exam. A low-vision exam is different from your regular eye exam.

A low-vision specialist can help you to maximize the vision that you do have with the aid of devices that can magnify things you need to see. While you may not be able to do everything you used to, such as driving, you can continue many daily activities.

Outlook

While there is no cure for AMD, the push for sight-saving new treatments continues. These run the gamut from retinal cell transplants to gene therapy to chip implants to simulate vision. All this means that for those contending with this condition, the outlook has never been better.

If you have been diagnosed with AMD, see a low-vision specialist for vision rehabilitation to maximize your remaining sight.