Fact Sheet: Age-related macular degeneration

 

What is macular degeneration and what causes it?

There are so many sensory cells packed into such a small space in the macula, that it is no easy task for the body to remove the by-products of metabolism. It is quite common then for these to build up into little spots called drusen. They are a sign of so-called maculopathy. This condition is not noticeable at first, and does not always lead to problems. People with large drusen do have a higher risk of developing age-related macular degeneration (AMD). If people over the age of 50 have serious problems with vision that are not caused by other diseases, the condition is called AMD.

AMD leads to a loss of the most detailed part of our sight. This part is called our central vision. Precisely those things that we want to look at closely get blurry or distorted. Central vision is important for things like reading, driving and recognizing faces. Objects at the edge of our field of vision generally remain visible, but they cannot be recognized very well.

We do not know exactly what causes AMD. In some families no one ever develops AMD, even as they get much older. If a close relative already has AMD, your own risk is somewhat higher. It is also known that it happens to people who smoke more often and, on average, earlier than to people who don’t.

Some researchers suppose that AMD is the result of the very intensive metabolism activity that happens in the sensory cells of the retina. They need a lot of oxygen. Using oxygen, though, results in a lot of so-called free radicals, which gradually do a bit of harm in the tissues. Light encourages this process, too. It is possible that for some people the ability to repair this damage cannot keep up.

This theory has not yet given us any concrete actions that can definitely prevent AMD. One of the common recommendations is to take anti-oxidants, like beta-carotene (a building block of vitamin A) and vitamin E. These vitamins, along with other dietary supplements like zinc, omega-3 fatty acids and ginkgo biloba, are all being tested by researchers to see if they might prevent AMD. But none has yet been proven to definitely work.

What is the difference between ‘dry’ and ‘wet’ AMD?

There are two types of AMD. About 8 out of 10 people with AMD have the type called 'dry' AMD. In this form, the light-sensitive cells of the retina are destroyed. Dry AMD is more common than the other form.

The other 2 out of 10 people with the condition have what is called 'wet' AMD. New blood vessels growing under the retina and lifting it are the cause of wet AMD. For this reason, doctors may also call this condition neovascular AMD. These vessels may leak, allowing blood or fluids to seep into the retina and to damage the cells. In industrialized countries, this is probably the main reason for loss of sight.

What are the treatment options for AMD?

There are no treatments that have been proven to be effective for dry AMD. People with dry AMD are less at risk of losing their sight, though.

There are several treatment options for wet AMD, including

• new drugs that are injected into the eye, such as Lucentis, Macugen and Avastin,
• photodynamic therapy, as laser treatment with medication,
• laser therapy,
• surgical removal of new blood vessels.

You can read more about the new medications in our fact sheet.

Photodynamic therapy is one of the treatments most commonly used for AMD. Sometimes it is used with an additional treatment, for example together with one of the newer drugs. As long as the loss of vision has not gone too far, it can slow progress of the condition for some people. In Germany, the costs of photodynamic therapy for people with wet AMD are covered by health insurance.

Photodynamic therapy is done every 3 or 4 months. A light-sensitive medicine called verteporfin is injected into a vein, where it spreads out through the bloodstream. Then a laser is used to send a microscopic beam of light through the eye's lens. When the light from the laser reaches the medicine in the blood vessels, it reacts to destroy the unwanted blood vessels. The dose needs to be at a level that ensures the retina itself is not damaged.

Using the results of trials on people with wet AMD, it is possible to estimate that 64 out of every 100 people would have a noticeable loss of vision after 2 years without treatment. But for people who had 5 sessions of photodynamic therapy over those 2 years, sight would be worse in 50. In other words: about 14 out of every 100 people benefit from the treatment. But photodynamic therapy cannot repair damage that has already happened in the retina.

The therapy does have adverse effects, though. Verteporfin treatment causes new sight problems in 1 to 5 out of every 100 people. About 2 out of every 100 people have temporary back pain. Important: because sunlight can also activate the medicine in the skin, people need to avoid direct sunlight for several days after treatment. You can read more about research on laser therapy in our research summary.

Laser therapy was one of the early treatment options developed for wet AMD. Today it is not used very often, usually only for cases of a rarer form of AMD called extrafoveal AMD, in which the unwanted blood vessels do not grow directly under the center of the retina.

In laser therapy, abnormal blood vessels are destroyed. Healthy parts of the eye can also be damaged at the same time though. About 15 out of 100 people who have had laser therapy can see better afterwards (15%). But there is also a disadvantage: immediately after treatment vision can temporarily worsen. Because of this, people thinking about getting this treatment should prepare themselves for the situation that their vision gets worse before it gradually gets better. For AMD in the center of the eye, laser therapy would cause too much damage.

There are other forms of laser treatment, but these have not been as well studied as photodynamic therapy.

Other treatment options, including drugs, radiotherapy and implants are in the experimental phase.

What general options to protect our sight are there?

Although they are often recommended, it is not yet known whether or not vitamins can help prevent AMD. The same is true for other specific preventive measures for this condition. Yet there are several general things that help to protect sight.

People with diabetes are at higher risk of eye problems and loss of sight. But so-called diabetic retinopathy is caused by other factors than AMD. In diabetes, the risk of loss of sight can be lowered with good blood glucose control and early treatment of changes in the retina.

Computer screens probably do not harm the eyes. While a long time at the computer and lots of reading might cause eye strain and headaches, it will not damage the functioning of the retina.

Author: German Institute for Quality and Efficiency in Health Care (IQWiG)

© IQWiG (Institute for Quality and Efficiency in Health Care)