Clemson Eye - Macular Degeneration

Age-Related Macular degeneration (AMD)

Macular degeneration is a progressive eye condition affecting as many as 15 million Americans and millions more around the world. The disease attacks the central part of the retina or ‘macula’, where our sharpest central vision occurs. Although it rarely results in complete blindness, it robs the individual of all but the outermost, peripheral vision, leaving only dim images or black holes at the center of vision.

There are several forms of macular degeneration, but the fastest growing form is age-related macular degeneration (AMD). AMD is the number one cause of severe vision loss and legal blindness in adults over 60 in the U.S. As our population ages, and the "baby boomers" advance into their 60's and 70's, we will see a virtual epidemic of AMD. Perhaps 14%-24% of the U.S. population aged 65-74 years and 35% of people aged 75 years or more have the disease.

Although it never causes total blindness by itself, age-related macular degeneration robs those affected of their sharp central vision and can dim contrast sensitivity and color perception. It destroys the clear, "straight ahead" central vision necessary for reading, driving, identifying faces, watching television, doing fine detailed work, safely navigating stairs and performing other daily tasks we take for granted. Peripheral vision may not be affected, and it is possible to see "out of the corner of your eye". Vision Rehabilitation and assistive devices can help people use their remaining vision effectively. The impact of developing AMD can be devastating to those who were independent and active prior to the onset of this impairment. Their visual world gradually diminishes into a vague blur, making ordinary daily activities challenging.

There are two types of AMD - "wet" or neovascular and "dry" or atrophic. There is no cure for AMD, but new treatments are available for the wet form of the disease. There is no treatment for the dry form, but training and special devices can promote independence and a return to favorite activities.

Related Links:

Macular Degeneration Foundation
www.eyesight.org

Macular Degeneration Network
www.macular-degeneration.org

Association for Macular Disease, Inc
www.macula.org

Foundation Fighting Blindness
www.blindness.org

National Eye Institute
www.nei.nih.gov

AMDhelp
www.amdhelp.com

Types of AMD

There are two types of age related macular degeneration. One form is known as "wet" and the other is "dry". It is possible to experience both forms at the same time, in one or both eyes. It is not uncommon for a patient with the "dry" form to develop the "wet" form later. The onset and progression of either type do not follow any particular pattern. In its earliest stages, AMD can be difficult to diagnose. Sometimes it progresses so slowly that people do not notice a change in their vision. Years may go by before they see an ophthalmologist or eye care professional. In other cases, the deterioration is very rapid and can appear to happen overnight.

Retina of an Eye with Dry AMD

Dry AMD is the most common type affecting 90% of all people who have the condition. In the dry form, there is a breakdown or thinning of the retinal pigment epithelial cells (RPE) in the macula. These RPE cells are important to the health of the retina. They provide nutritional support to the thousands of light-sensitive photoreceptor cells in the retina. The death or degeneration of these cells is called atrophy. Hence, dry AMD is often referred to as atrophic AMD. It is characterized by the presence of drusen (dots of yellow crystalline deposits that develop within the macula) and thinning of the macula. Dry or atrophic MD reduces one's central vision and can effect color perception. Generally, the damage caused by the "dry" form is not as severe or rapid as that of the "wet" form. However, over time, it can cause profound vision loss. Unfortunately, there is no proven cure or treatment. The recent “Age-Related Eye Disease Study” or AREDS, demonstrated a modest beneficial effect from certain vitamin supplements in slowing down the progression of dry AMD.

Retina of an Eye with Wet AMD

The wet form is the more severe type of AMD. Although it affects only 10 percent of those who have the condition, it accounts for 90 percent of the severe vision loss caused by macular degeneration. With this type, the membrane underlying the retina thickens, then breaks. The oxygen supply to the macula is disrupted and the body responds by growing new, abnormal blood vessels. These begin to grow through the breaks of the membrane behind the retina towards the macula, often raising the retina.

To visualize this, imagine the roots of a tree growing and spreading until they actually uproot a sidewalk. Then imagine rainwater seeping up throughout the cracks. These abnormal blood vessels (the "roots) tend to be very fragile. They often grow, leak or bleed, causing scarring of the macula. This damage to the macula results in rapid central vision loss. Once this vision is destroyed, it cannot be restored.

There are several treatment options for wet AMD which can be very effective if applied early. For more information on treatment, click here. To learn about ongoing research and experimental treatments, click here.

Tests your Doctor May Use

In order to diagnose macular degeneration, your doctor may perform one or several photographic procedures. These are all non-invasive and painless. For two of them, you will have a dye injected into your arm with a very small needle. Most people experience very little discomfort, though the light from the camera can be glaring.

Fluorescein Angiogram

A technician will perform a test called a fluorescein angiogram. This involves injecting a dye into the patient's arm. The dye travels quickly through the body. When it reaches the back of the eye, a rapid sequence of photos of the retina is taken. The procedure is not invasive - the photos are taken like regular pictures. The eye is dilated, so the retina can be seen through the wide open pupil. These photos show what changes have taken place in the retina and where abnormal blood vessels are located.

Optical Coherence Tomography (OCT)

Your doctor may also take specialized photos that show the layers of the retina in cross section. There is no dye or injection involved. This special photograph lets the doctor see the thickness of the retina and any inflammation and fluids. As treatment continues, additional OCT images can show the effect of the therapy and can guide future treatment.

Indocyanine Green (ICG) Angiography

A procedure similar to fluorescein angiography, ICG angiography uses Indocyanine green dye which can show more detail than flourescein angiography. It also uses a dye that is injected into the eye and then digital photographs are taken.

Most patients report that their first sign of AMD was the rapid onset of prolonged, distorted vision. Straight lines like telephone wires and door frames appear to be wavy. If you notice any distorted or missing areas of vision, consult your ophthalmologist promptly.

Amsler Grid Testing

The Amsler Grid is a simple test of your central vision. It will alert you to any early changes that may indicate a problem with macular degeneration or a worsening of your condition.

The Amsler Grid looks like graph paper, with dark lines forming a square grid. Some versions have white lines on a dark background.

One of the first signs of macular degeneration can be wavy, broken or distorted lines OR a blurred or missing area of vision. The Amsler Grid can help you spot these early. Early detection of wet AMD is critical because laser or other treatments, when indicated, are most successful when performed before damage occurs. Since dry AMD can lead to development of wet AMD, most patients should use the Amsler Grid. Check with your eye doctor to find out how often you should use this test.

Instructions

1. Wear your reading glasses

2. Hold the Amsler grid at a normal reading distance

3. Cover one eye

4. Look at the dot in the center of the grid

5. Note how the lines and squares appear

6. Test the other eye in the same manner

Action

All of the lines should be straight and the squares of a uniform size.
If you note any changes in the appearance of the grid, such as distortion, blurring, discoloration, dark or missing areas of the grid, or any other changes, call and see your eye doctor immediately. Do not wait to see if the changes will clear on their own. Timely treatment is vital to safeguarding your vision.

Introducing PHP

An exciting new technology as been recently introduced that promises to be an effective tool for early detection of age-related macular degeneration (AMD). Called the PreView PHP™ (Preferential Hyperacuity Perimetry), it identifies deviations in the retina using a vision test based upon the hyperacuity phenomenon. Instead of a white stimulus on a white background, PHP uses a hyperacuity stimulus. This is based on the theory of Vernier hyperacuity, which is the human ability to perceive minute differences in the relative spatial localization of two objects in space. Our ability to pick out an object that's not in the same line as nearby objects is extremely sensitive; much more so than our ability to read letters on a Snellen chart.

During the test, which can be administered in 5 – 6 minutes per eye, a series of lines are presented on a screen with varying levels of distortion. The patient is asked to identify these areas with a pointer. If the patient has early AMD this may produce other distortions in the lines which the patient will identify. An algorithm in the computer determines the depth of the visual field defects and generates a printout that quantifies the size of a lesion. The printout provides reliability parameters and maps out a defect. It's more sensitive than asking a patient to draw on an Amsler grid.

A recent study showed that PHP testing yielded high percentages (over 80%) of sensitivity in detecting new choroidal neovascularization (‘wet’ AMD changes) in 122 patients presenting with intermediate-through-advanced AMD. This is an improvement over previous methods of early diagnosis, which supports the researchers' conclusion that the PHP should be considered as a useful adjunct to the management of the intermediate stage of AMD.

This exciting technology is available at Clemson Ophthalmology.

Vision Examples

What Does the AMD Patient See?

When you go to your ophthalmologist for a regular check-up, you should receive a dilated retinal examination. If there are signs of macular degeneration, your doctor will notice the presence of drusen or may notice new blood vessels beginning to grow in the macula.

For many people, the first sign of AMD is something they notice themselves. Straight lines like doorways or telephone wires may appear wavy or disconnected. When you look at a person, her face may be blurred while the rest of her is in focus. Lines of print may be blurred in the center or the lines may be crooked. For some people, there is a sudden blurring or loss of sight in the center of vision. This would be a sign of wet macular degeneration. For any sudden change, you should contact your ophthalmologist immediately.

Here are some examples of what a patient with macular degeneration might see. Figure 1 shows the typical wavy lines at the center of vision. Figure 2 shows the missing image that is characteristic either of wet macular degeneration or of the later stages of dry macular degeneration

Clemson Opthalmology

Age-Related Macular degeneration (AMD)

Types of AMD

Tests your Doctor May Use

Introducing PHP

Vision Examples