How the Eye Works
This is a brief video that shows a short overview
of the anatomy and the function of the eye.
What is macular degeneration?
Macular degeneration is a deterioration or breakdown of the macula. The macula is a small area in the retina at the back of the eye that allows you to see fine details clearly and perform activities such as reading and driving.
When the macula does not function correctly, your central vision can be affected by blurriness, dark areas or distortion. Macular degeneration affects your ability to see near and far, and can make some activities--like threading a needle or reading --difficult or impossible.
Although macular degeneration reduces vision in the central part of the retina, it does not affect the eye's side, or peripheral, vision. For example, you could see the outline of a clock but not be able to tell what time it is.
Macular degeneration alone does not result in total blindness. Even in more advanced cases, people continue to have some useful vision and are often able to take care of themselves. In many cases, macular degeneration's impact on your vision can be minimal.
What causes macular degeneration?
Many older people develop macular degeneration as part of the body's natural aging process. There are different kinds of macular problems, but the most common is age-related macular degeneration (AMD). Exactly why it develops is not known, and no treatment has been uniformly effective. Macular degeneration is the leading cause of severe vision loss in Caucasions over 65.
The two most common types of AMD are "dry" (atrophic) and "wet" (exudative):
"Dry" (atrophic) macular degeneration
Most people have the "dry" form of AMD. It is caused by aging and thinning of the tissues of the macula. Vision loss is usually gradual.
"Wet" (exudative) macular degeneration
The "wet" form of macular degeneration accounts for about 10-15% of all AMD cases. It results when abnormal blood vessels form underneath the retina at the back of the eye. These new blood vessels leak fluid or blood and blur central vision. Vision loss may be rapid and severe.
What are the symptoms of macular degeneration?
Macular degeneration can cause different symptoms in different people. The condition may be hardly noticeable in its early stages. Sometimes only one eye loses vision while the other eye continues to see well for many years.
But when both eyes are affected, the loss of central vision may be noticed more quickly. Following are some common ways vision loss is detected.
- words on a page look blurred;
- a dark or empty area appears in the center of vision;
- straight lines look distorted, as in the following diagram:
Can the dry form turn into the wet form?
Yes. All people who have the wet form had the dry form first.
The dry form can advance and cause vision loss without turning into the wet form. The dry form also can suddenly turn into the wet form, even during early stage AMD. There is no way to tell if or when the dry form will turn into the wet form.
Who is at risk for AMD?
The greatest risk factor is age. Although AMD may occur during middle age, studies show that people over age 60 are clearly at greater risk than other age groups. For instance, a large study found that people in middle-age have about a 2 percent risk of getting AMD, but this risk increased to nearly 30 percent in those over age 75.
Other risk factors include:
§ Smoking. Smoking may increase the risk of AMD.
§ Obesity. Research studies suggest a link between obesity and the progression of early and intermediate stage AMD to advanced AMD.
§ Race. Whites are much more likely to lose vision from AMD than African Americans.
§ Family history. Those with immediate family members who have AMD are at a higher risk of developing the disease.
§ Gender. Women appear to be at greater risk than men.
Can my lifestyle make a difference?
Your lifestyle can play a role in reducing your risk of developing AMD.
§ Eat a healthy diet high in green leafy vegetables and fish.
§ Don't smoke.
§ Maintain normal blood pressure.
§ Watch your weight.
How is macular degeneration diagnosed?
Many people do not realize that they have a macular problem until blurred vision becomes obvious. Your ophthalmologist (Eye M. D.) can detect early stages of AMD during an eye examination that includes the following:
- a simple vision test in which you look at a chart that resembles graph paper (Amsler grid);
- viewing the macula with an ophthalmoscope;
- taking special photographs of the eye called fluorescein angiographs to find abnormal blood vessels under the retina.
How is macular degeneration treated?
Although the exact causes of macular degeneration are not fully understood, antioxidant vitamins and zinc may reduce the impact of AMD in some people.
A large scientific study (the AREDS study) found that people at risk for developing advanced stages of AMD lowered their risk by about 25% when treated with a high-dose combination of vitamin C, vitamin E, beta carotene and zinc. Among those who have either no AMD or very early AMD, the supplements did not appear to provide an apparent benefit.
Deposits under the retina called drusen are a common feature of macular degeneration. Drusen alone usually do not cause vision loss, but when they increase in size or number, this generally indicates an increased risk of developing advanced AMD. People at risk for developing advanced AMD have significant drusen, prominent dry AMD, or abnormal blood vessels under the macula in one eye ("wet" form).
It is very important to remember that vitamin supplements are not a cure for AMD, nor will they restore vision that you may have already lost from the disease. However, specific amounts of these supplements do play a role in helping some people at high risk for advanced AMD to maintain their vision. You should speak with your ophthalmologist to determine if you are at risk for developing advanced AMD, and to learn if supplements are recommended for you.
Laser photodynamic therapy
Certain types of "wet" AMD can be treated with photodynamic therapy where a focused beam of light is used to slow or stop leaking blood vessels that damage the macula. This procedure may preserve sight overall, though it does not usually restore lost sight to normal and is not a cure.
Some patients with wet AMD can now be treated with new drugs that are injected into the eye (anti-VEGF therapy). Abnormally high levels of a specific growth factor occur in eyes with wet AMD and promote the growth of abnormal new blood vessels. This drug treatment blocks the effects of the growth factor.
You will need multiple injections that may be given as often as monthly. The eye is numbed before each injection. After the injection, you will remain in the doctor's office for a while and your eye will be monitored. This drug treatment can help slow down vision loss from AMD and in some cases improve sight.
Despite advanced medical treatment, many people with macular degeneration still experience some vision loss. To help you adapt to lower vision levels, your ophthalmologist can prescribe optical devices or refer you to a low-vision specialist or center. A wide range of support services and rehabilitation programs are also available to help people with macular degeneration maintain a satisfying lifestyle.
Because side vision is usually not affected, a person's remaining sight is very useful. Often, people can continue with many of their favorite activities by using low-vision optical devices such as magnifying devices, closed-circuit television, large-print reading materials, and talking or computerized devices.
Testing your vision with the Amsler grid
You can check your vision daily by using an Amsler grid like the one pictured here. You may find changes in your vision that you wouldn't notice otherwise. Putting the grid on the front of your refrigerator is a good way to remember to look at it each day.
If you would like to have an Amsler grid, we would be happy to give you one. Just call or stop in our office:
Eye Physicians and Surgeons
Mercy Medical Plaza
540 E. Jefferson St., Suite #201
Iowa City, IA 52245
Toll-free in Iowa: (800) 338-3623
To Use the Grid:
- Wear your reading glasses and hold this grid 12-15 inches away from your face in good light.
- Cover one eye.
- Look directly at the center dot with the uncovered eye.
- While looking directly at the center dot, note whether all lines of the grid are straight or if any areas are distorted, blurred or dark.
- Repeat this procedure with the other eye.
- If any area of the grid looks wavy, blurred or dark, call Eye Physicians and Surgeons or another ophthalmologist right away.