Dry macular degeneration

Definition

Age-related macular degeneration is a chronic eye disease marked by deterioration of tissue in the part of your eye that's responsible for central vision. The deterioration occurs in the macula (MAK-u-luh), which is in the center of the retina — the layer of tissue on the inside back wall of your eyeball.

Macular degeneration doesn't cause total blindness, but it worsens your quality of life by blurring or causing a blind spot in your central vision. Clear central vision is necessary for reading, driving, recognizing faces and doing detail work.

Macular degeneration tends to affect adults age 50 and older. Dry macular degeneration, in which tissue deterioration is not accompanied by bleeding, is the most common form of the disease.

Symptoms

Dry macular degeneration usually develops gradually and painlessly. You may notice these vision changes:

* The need for increasingly bright light when reading or doing close work
* Increasing difficulty adapting to low light levels, such as when entering a
dimly lit restaurant
* Increasing blurriness of printed words
* A decrease in the intensity or brightness of colors
* Difficulty recognizing faces
* Gradual increase in the haziness of your overall vision
* Blurred or blind spot in the center of your visual field combined with a
profound drop in the sharpness (acuity) of your central vision

Your vision may falter in one eye while the other eye remains fine for years. You may not notice any or much change because your good eye compensates for the weak one. Your vision and lifestyle begin to be dramatically affected when this condition develops in both eyes.

Hallucinations

Additionally, some people with macular degeneration may experience visual hallucinations as their vision loss becomes more severe. These hallucinations may include unusual patterns, geometric figures, animals or even faces. You might be afraid to discuss these symptoms with your doctors or friends and family for fear you'll be considered crazy. However, such hallucinations aren't a sign of mental illness. In fact, they're so common that there's a name for this phenomenon — Charles Bonnet syndrome.

When to see a doctor

See your eye doctor — particularly after age 50 — if:

* You notice changes in your central vision
* Your ability to see colors and fine detail becomes impaired

One way to monitor your eyes to determine if you may need to visit your eye doctor is to check your vision regularly using an Amsler grid. This simple test may help you detect changes in your sight that you otherwise may not notice.

Here's how to perform the test:

* Hold the grid 14 inches (about 36 centimeters) in front of you in good light.
Use your corrective glasses or reading glasses if you normally wear them.
* Cover one eye.
* Look directly at the center dot with your uncovered eye.
* While looking at this dot, determine whether all of the lines of the grid appear
straight, uninterrupted and have the same contrast.
* Repeat the above steps with your other eye.
* If any part of the grid is missing or looks wavy, blurred or dark, contact your
eye doctor immediately.

Causes

The exact cause of dry macular degeneration is unknown, but the condition develops as the eye ages. The initial site of change is not in the light-sensitive cells of the macula, but in the retinal pigment epithelium (RPE), a single layer of cells located just behind the retina close to the back wall of your eye.

Your macula is an area about two-tenths of an inch (5 millimeters) in diameter at the center of your retina. This small part of your eye is responsible for clear vision, particularly in your direct line of sight.

The macula consists of millions of densely packed light-sensitive cells called cones and rods. Cones and rods have two segments: An inner segment controls cell functions and produces proteins responsive to light, and an outer segment stores and makes use of these proteins.

As they absorb light, outer segment proteins become degraded and eventually are shed as waste. Meanwhile, the inner segments continuously provide replacements for the outer segments. One function of the cells of the RPE is to remove the outer segments that are shed.

As the eye ages, cells in the RPE begin to deteriorate (atrophy) and lose their pigment. As a consequence, the RPE becomes less efficient in removing outer segment waste. When that happens, the normally uniform reddish color of the macula (as seen with an ophthalmoscope) takes on a mottled appearance. Drusen — yellow, fat-like deposits — begin to appear under the cones and rods. As the drusen and mottled pigmentation continue to develop, your vision gradually deteriorates.

Based on this progression, dry macular degeneration is categorized in three stages:

* Early stage. Several small drusen or a few medium-sized drusen are detected on
the macula in one or both eyes. Generally, there's no vision loss in the
earliest stage.
* Intermediate stage. Many medium-sized drusen or one or more large drusen are
detected in one or both eyes. At this stage, your central vision may start to
blur and you may need extra light for reading or doing detail work.
* Advanced stage. Several large drusen, as well as extensive breakdown of light-
sensitive cells in the macula, are detected. These features cause a well-defined
spot of blurring in your central vision. The blurred area may become larger and
more opaque over time.

Macular degeneration almost always starts out as the dry form. Dry macular degeneration may initially affect only one eye but, in most cases, both eyes eventually become involved.

Risk factors

Contributing factors for development of macular degeneration include:

* Age. In the United States, macular degeneration is the leading cause of severe
vision loss in people age 60 and older.
* Family history of macular degeneration. If someone in your family had macular
degeneration, your odds of developing macular degeneration are higher. In recent
years, researchers have identified some of the genes associated with macular
degeneration. In the future, genetic screening tests may be helpful for
assessing early risk of the disease.
* Race. Macular degeneration is more common in whites than it is in other groups,
especially after age 75.
* Sex. Women are more likely than men to develop macular degeneration, and because
they tend to live longer, women are more likely to experience the effects of
severe vision loss from the disease.
* Cigarette smoking. Exposure to cigarette smoke doubles your risk of macular
degeneration. Cigarette smoking is the single most preventable cause of macular
degeneration.
* Obesity. Being severely overweight increases the chance that early or
intermediate macular degeneration will progress to the more severe form of the
disease.
* Light-colored eyes. People with light-colored eyes appear to be at greater risk
than do those with darker eyes.
* Exposure to sunlight. Although the retina is more sensitive to shorter
wavelengths of light, including ultraviolet (UV) light, only a small percentage
of ultraviolet light actually reaches the retina. Most ultraviolet light is
filtered by the transparent outer surface of your eye (cornea) and the natural
crystalline lens in your eye. Some experts believe that long-term exposure to
ultraviolet light may increase your risk of developing macular degeneration, but
this risk has not been proved and remains controversial.
* Low levels of nutrients. This includes low blood levels of minerals, such as
zinc, and of antioxidant vitamins, such as A, C and E. Antioxidants may protect
your cells from oxygen damage (oxidation), which may partially be responsible
for the effects of aging and for the development of certain diseases such as
macular degeneration.
* Cardiovascular diseases. These include high blood pressure, stroke, heart attack
and coronary artery disease with chest pain (angina).

Preparing for your appointment

To check for macular degeneration, a dilated eye exam is necessary. Make an appointment with a doctor who specializes in eye care — an optometrist or an ophthalmologist — who can evaluate your condition and perform a complete eye exam.

What you can do

Appointments can be brief. Make the best use of that limited time by preparing beforehand.

* Be aware of any pre-appointment restrictions. When you make the appointment, ask
if there's anything you need to do in advance.
* Write down any symptoms you're experiencing, including any that may seem
unrelated to your vision problem.
* Make a list of all medications, as well as any vitamins or supplements, that
you're taking.
* Ask a family member or friend to accompany you, if possible. Having your pupils
dilated for the eye exam may compromise your vision for a time afterward. You
may need someone else to drive or accompany you from your appointment.

Questions to ask your eye doctor

* What kind of macular degeneration do I have?
* What is the visual acuity in my central vision?
* How advanced is my macular degeneration?
* Will I experience further vision loss?
* Will taking a vitamin or mineral supplement help prevent further vision loss?
* What's the best way to monitor my vision for any changes?
* What low-vision aids or adaptive devices might be helpful to me?

Questions your eye doctor may ask

* When did you first notice your vision problem?
* Does the condition affect one or both eyes?
* Do you have trouble seeing things near you, at a distance or both?

Tests and diagnosis

Diagnostic tests for macular degeneration may include:

* An eye examination. One of the things your eye doctor looks for while examining
the inside of your eye is the presence of drusen and mottled pigmentation in the
macula. The eye examination includes a simple test of your central vision and
may include testing with an Amsler grid. If you have macular degeneration, when
you look at the grid some of the straight lines may seem faded, broken or
distorted. By noting where the break or distortion occurs — usually on or near
the center of the grid — your eye doctor can better determine the location and
extent of your macular damage.

Regular screening examinations can detect early signs of macular degeneration
before the disease leads to vision loss.

* Angiography. To evaluate the extent of the damage from macular degeneration,
your eye doctor may use fluorescein angiography. In this procedure, fluorescein
dye is injected into a vein in your arm and photographs are taken of the back of
the eye as the dye passes through blood vessels in your retina and choroid. Your
doctor then uses these photographs to detect changes in macular pigmentation or
to identify small macular blood vessels.

Your doctor may also suggest a similar procedure called indocyanine green
angiography. Instead of fluorescein, a dye called indocyanine green is used.
This test provides information that complements the findings obtained through
fluorescein angiography.

* Optical coherence tomography. This noninvasive imaging test helps identify and
display areas of retinal thickening or thinning. Such changes are associated
with macular degeneration. This test can also reveal the presence of abnormal
fluid in and under the retina or the RPE. It's often used to help monitor the
response of the retina to macular degeneration treatments.

Treatments and drugs

There's no treatment available to reverse dry macular degeneration. But this doesn't mean you'll eventually lose all of your sight. Dry macular degeneration usually progresses slowly, and many people with the condition are able to live relatively normal, productive lives, especially if only one eye is affected. Dry macular degeneration can, however, develop into the more rapidly progressive wet type of macular degeneration at any time.

Taking a high-dose formulation of antioxidants and zinc may reduce progression of dry macular degeneration to advanced macular degeneration. The National Eye Institute-sponsored Age-Related Eye Disease Study (AREDS) showed that a daily supplement of 500 milligrams (mg) of vitamin C, 400 international units (IU) of vitamin E, 15 mg of beta carotene (often as vitamin A — up to 25,000 IU), 80 mg of zinc (as zinc oxide) and 2 mg of copper (as cupric oxide) reduced the risk of progressing to moderate or severe vision loss by up to 25 percent.
Lifestyle and home remedies

Macular degeneration doesn't affect your side (peripheral) vision and usually doesn't cause total blindness. But it can rob you of your central vision — which is important for driving, reading and recognizing people's faces. A low-vision center may be able to assess your visual capabilities and suggest certain optical and household devices that can be helpful for some near-vision tasks. Ask your eye doctor if there are any low-vision centers in your area.

There are ways to cope with impaired vision. Below are a few suggestions:

* Use caution when driving. First, check with your doctor to see if driving is
still safe based on your current visual acuity. When you do drive, there are
certain situations to avoid. For example, don't drive at night, in heavy traffic
or in bad weather.
* Seek help traveling. Use public transportation or ask family members to help,
especially with night driving.
* Travel with others. Contact your local area agency on aging for a list of vans
and shuttles, volunteer driving networks or ride shares.
* Get good glasses. Optimize the vision you have with the right glasses, and keep
an extra pair in the car.
* Use magnifiers. Large-print books and magazines can help you read more easily.
* View with large type on the Internet. Look for Web sites that use large-sized
type fonts, or change the font size on your display.
* Obtain specialized appliances. Some clocks, radios, telephones and other
appliances have extra-large numbers.
* Have proper light in your home. This will help with reading and other activities.
* Remove home hazards. Eliminate throw rugs and other possible tripping hazards in
your home.
* Ask friends and family members for help. Tell them about your vision problems so
that they can help you perform certain tasks and help you recognize people.
* Don't become socially isolated. A common frustration of people with macular
degeneration is the inability to recognize other people and greet them by name.
If this happens to you, try asking people you know to say hi and tell you their
names when you meet them on the street or in other situations so that you can
greet them back.
* Take advantage of online networks. The Internet is a good source for support
groups and resources for people with macular degeneration.

Alternative medicine

Some people have turned to complementary or alternative therapies, such as bilberry, ginkgo and shark cartilage, in the belief that they can help prevent the progression of macular degeneration.

However, there's no conclusive evidence that any of these products are effective for macular degeneration, and some may interact with other medications you're taking. Check with your doctor before taking any dietary or herbal supplement.
Prevention

The following measures may help you avoid macular degeneration:

* Eat foods containing antioxidants. Foods with antioxidants are those rich in
vitamins A, C and E. People who eat diets rich in vegetables, particularly leafy
green vegetables, may have a lower risk of macular degeneration. The National
Eye Institute is currently sponsoring a clinical trial to assess the efficacy of
three specific antioxidants — lutein, zeaxanthin and omega-3 fatty acids — in
lowering the risk of macular degeneration. Lutein and zeaxanthin are found in
high concentrations in egg yolks, corn, and spinach and other green leafy
vegetables. Omega-3 fatty acids are found in fish as well as other foods such as
almonds.
* Take antioxidant and zinc supplements. For people with moderate to advanced
macular degeneration, findings from the National Eye Institute-sponsored
Age-Related Eye Disease Study (AREDS) indicate that taking high doses of zinc,
beta carotene, and vitamins C and E is effective in reducing the risk of further
vision loss. However, beta carotene has been linked to increased risk of lung
cancer in smokers. Too much vitamin E can be toxic. Ask your doctor about these
supplements before trying anything on your own.
* Eat fish. A diet rich in the omega-3 fatty acids found in fish can result in a
reduced risk of macular degeneration.
* Stop smoking. Smokers are more likely to develop macular degeneration than are
nonsmokers. Ask your doctor for help to stop smoking.
* Manage your other diseases. For example, if you have cardiovascular disease or
high blood pressure, take your medication and follow your doctor's instructions
for controlling the condition.
* Get regular eye exams. Early detection of macular degeneration increases your
chances of preventing serious vision loss. If you're older than 40, get an exam
every two to four years, and older than 65, every year or two. If you have a
family history of macular degeneration, have your eyes examined more frequently.
* Screen your vision regularly. If you've received a diagnosis of early-stage
macular degeneration, your doctor may suggest that you regularly monitor your
vision at home with an Amsler grid. Doing so may help you to detect subtle
changes in your vision at the earliest possible time and seek help promptly.

If you have some vision loss because of macular degeneration, your eye doctor can prescribe optical devices called low-vision aids that will help you see better for close-up work. Or your doctor may refer you to a low-vision specialist. In addition, a wide variety of support services and rehabilitation programs are available that may help you adjust your lifestyle.

By Mayo Clinic Staff
Aug. 26, 2008