A Look at Macular Degeneration: The Leading Cause of Blindness

**By Connie Chen, MD**

macular-degenrationAlthough their fame was the result of individual talent, Stephen King, Georgia O’ Keefe and Bob Hope all share something in common – they all suffered from macular degeneration.

Often referred to as age-related macular degeneration (ARMD or AMD), as many as 11 million Americans have some form of AMD and it is the leading cause of blindness in the United States. The condition mainly affects people 65 and older. Although some macular complications affect younger people, which is sometimes referred to as macular degeneration, the term generally refers to age-related macular degeneration. The part of the eye affected by AMD is the macula or the sensitive part of the retina that is responsible for sharp, central vision.

Symptoms

Unfortunately, vision loss early in the course of macular degeneration is so gradual that most people do not notice it, and pain is not usually experienced. However, as the disease progresses, vision may be blurred and objects may appear distorted. In addition, people may complain of missing letters in words or having difficulty seeing smaller print.

In more severe cases, there may be a significant loss or graying of central vision, while peripheral vision remains unchanged. A person’s ability to adapt to different lighting environments may also be affected.

Causes

Macular degeneration is related to aging. Despite the chance that someone’s environment may contribute to the development of AMD, current research is focusing on certain genes that some people possess, which may increase or decrease their risk for developing the disease.

In macular degeneration, a noticeable change happens in the deeper retinal layers. Cellular debris starts to build up, which produces yellow deposits known as “drusen.”

In some cases, the retina’s release of chemical mediators can lead to new blood vessel growth, or “neovascularization.” The new blood vessels are weak and may leak blood and fluid into the retinal tissue.

Risk factors

In addition to age, there are numerous known risk factors for developing age-related macular degeneration. They include smoking, family history and ethnicity.

Types

There are two major types of the disease, “dry” and “wet” macular degeneration.

Dry (or “non-neovascular”) AMD
Dry AMD is the most common type and makes up about 90 percent of all AMD cases. In dry AMD, a visible change happens in the deeper retinal layers, leaving areas of depigmentation, pigment clumping and drusen. Dry AMD usually advances very slowly. Although the amount of vision loss varies, it rarely results in legal blindness. However, some people may develop macular tissue atrophy, leading to vision loss.

Wet (or “neovascular”) AMD
Wet AMD makes up about 10 percent of all AMD cases. People affected by the dry form of AMD may have the disease progress to the wet form over time. In wet AMD, new blood vessel growth takes place under the retina. Despite these vessels being new, they are naturally frail. As the name indicates, the appearance is wet: fluid and blood leak from the new blood vessels, which causes vision loss. Scarring may also occur, causing major vision loss and often, legal blindness.

Diagnosis

An AMD diagnosis usually comes after a thorough eye exam by an ophthalmologist or optometrist.

Both distance and near vision are measured as part of the exam. In addition, a test named the “Amsler grid” is done to identify blind spots, vision distortions or wavy lines.

A dilated retinal exam is also performed. This allows the physician to see a magnified view of the macula. If AMD is suspected, a dye-injection test, called fluorescein angiogram (FA), might be done. Another diagnostic test, called optical coherence tomography (OCT), may also be performed. It allows a physician to look at all layers of the retina, not just the inner ones. If AMD is detected, the patient is referred to a retinal specialist.

Treatment

Unfortunately, there is currently no known cure for macular degeneration. Treatment focuses on delaying or lessening its progression and varies depending on the stage at diagnosis.

Based on the Age-Related Eye Disease Study (AREDS) – a major clinical trial sponsored by the National Eye Institute in 2001 – nutritional supplements with vitamins C and E, beta-carotene and zinc were shown to slow or delay the progression of dry AMD to advanced AMD by 28 percent in high-risk patients.

Treatment for wet AMD focuses on halting the fluid leakage from neovascularization. More recently, anti-vascular endothelial growth factor (anti-VEGF) medications have been used to treat macular degeneration. These drugs are injected into the eye and designed to shrink the growth of new blood vessels.

For people with significant loss of sight, low-vision centers and physicians can recommend certain products or home modifications that can sometimes restore functional vision and improve someone’s quality of life. These vision aides range from high-powered reading glasses or bifocals to telescopic lenses, hand-held devices, magnifiers and closed-circuit TVs. Other recommendations – such as using large-numbered clocks and stove dials, large-print books and electronic talking devices – may improve quality of life for a person affected by macular degeneration.

Although a cure for the disease has yet to be discovered, education, awareness and taking proactive steps, like having an annual eye exam, are simple steps that everyone can – and should – take to help maintain eye health and good vision throughout their lives.


Chen_Connie_2015Connie Chen, MD, is board certified in Ophthalmology. She is a retina specialist who practices at Virginia Mason Issaquah Medical Center and Virginia Mason Hospital & Seattle Medical Center. Dr. Chen speaks Mandarin and Spanish.

Trackbacks

  1. […] have to use glasses. In the event that vision must be further enhanced, adjustments could be made how to fix short sightedness without glasses actually years following the […]

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: