Alternative Names age related macular degeneration, central retinal degeneration
Definition The macula is the centre of the retina at the back of the eye. The images we see are sent to the macula and the rest of the retina. The macula has been likened to the film of a camera, which stimulates the brain so that we "see" the image in our mind. When the macula breaks down in a condition known as macular degeneration, decreased vision results.
What is going on in the body? The macula is the most critical portion of the retina. It is responsible for detailed vision. This function is necessary for reading and seeing distant objects in detail. When the macula breaks down or becomes damaged, vision is affected. Most of the time, this breakdown is age-related. It can also occur in younger people who have a genetic tendency toward the condition.
What are the signs and symptoms of the disease? Activities such as threading a needle, reading, seeing road signs at a distance, or recognising individuals across the room may become difficult or impossible. Macular degeneration reduces vision in the centre but does not affect the eye's peripheral or side vision. This means a person will be able to see large objects well. For example, a person may be able to see the outline of a clock but may not be able to tell what time it is. People with this problem may see objects as smaller or larger than they really are. For some people, the condition causes a dark or empty area in the centre of the field of vision. For others, straight lines look distorted and vertical or horizontal structures may appear to have a "pucker" in them.
This condition does not result in total blindness. Most people continue to have some useful vision. They are able to take care of themselves until the disease is very advanced. Also, vision is sometimes reduced in only one eye. The other eye may be able to see well for many years. When both eyes are affected, the individual will notice the problem more quickly.
What are the causes and risks of the disease? Most of the time, macular degeneration occurs as part of the normal ageing. It is more common in people with certain risk factors. These include:
For younger people, there may be a genetic link. This is especially true if there is a strong family history of the condition.
There are two common types of age-related macular degeneration.
The dry or atrophic type is caused by the gradual thinning of the macula and the loss of pigment in this area. This is due to ageing.
The wet or exudative form of the condition accounts only for about 10% of cases. It occurs when tiny, abnormal blood vessels form under the retina. These vessels leak fluid or blood. This can cause blurring of the central vision. When this occurs, vision loss may be rapid and severe.
What can be done to prevent the disease? Unfortunately, macular degeneration is not well understood and there are no known prevention methods. Some studies have shown that certain vitamins and minerals, such as vitamin E, vitamin C, and zinc, may slightly decrease the risk of developing this condition, but their effectiveness has not been proven. Avoidance of smoking may possibly lower a person's risk.
How is the disease diagnosed? Often, no symptoms are evident until the breakdown of the macula causes blurred vision. An opthalmologist (eye doctor) can detect the problem by dilating the person's pupil and looking at the back of the eye. In another test, individuals will look at a grid resembling graph paper. This is called an Amsler grid. If some of the lines appear lost or distorted, a problem with the retina exists.
Also, special photographs of the back of the eye may be done to reveal abnormal vessels under the retina. For this procedure, a fluorescent dye is injected into a vein in the arm. Rapid sequence pictures are then taken. This is called a fluorescein angiogram.
What are the long-term effects of the disease? With the dry form of the condition, central vision is gradually reduced over many years. Sometimes the condition will be stable for a number of years without worsening. In the wet type of macular degeneration, vision may decrease suddenly. If this happens in one eye, the other eye should be carefully monitored.
There is a marked loss of central vision in advanced macular degeneration. People tend to become frustrated with their condition. They are unable to drive, cannot read without bright light and magnification, and cannot recognise friends from a distance.
What are the treatments for the disease? Despite ongoing research, there is no cure for the dry form of macular degeneration at this time. Findings from recent studies suggest that anti-oxidant vitamins and minerals may slow the progress of the condition. At present, this form of the disease is managed by helping the person cope with the condition. Optical devices can sometimes be used to take advantage of a person's side vision. Low vision aids can also help affected individuals. These include:
magnifying devices
closed circuit television
large print reading materials
talking or computerised devices
The wet type of macular degeneration can sometimes be treated with laser surgery. This is an option for only about 25% of people with the condition. It is a brief and painless outpatient procedure. A laser beam is used to seal the leaking blood vessels that are damaging the macula. This leaves a small permanent scar or blind spot at the point of laser contact. However, more sight is preserved overall. Another promising procedure is still in the investigational stage. It involves injecting a substance into the veins that circulates to the abnormal retinal vessels. These blood vessels are then exposed to a specific wavelength of light. The result is the formation of scar tissue that shrinks the vessels before they have had a chance to leak and obscure vision.
How is the disease monitored? People with macular degeneration can check their vision daily by using an Amsler grid. This will reveal any sudden changes in either eye. An individual should test each eye separately. If the lines on the graph appear more wavy, blurred, or dark than before, then he or she should contact the opthalmologist immediately. The grid can be taped to a refrigerator or bathroom mirror to make it easily available.
Author: William Stevens, MD Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
