# Wednesday, September 24, 2008
                 

Age-related macular degeneration (AMD) has long been the leading cause of severe vision loss in Canadians. As age is one of the predominant risk factors for developing this condition, all Canadians over 50 years of age are strongly encouraged to learn more about the warning signs, as well as having an understanding of what this condition entails.

AMD gradually takes away central vision by the slow degeneration of the macula (a small area located in the very centre of the retina). Due to the slow and painless progress of this condition, AMD can remain undetected until it reaches the more advanced stage; routine eye exams however can detect it in its earlier stages. Therefore it is highly recommended that all people over 50 have their eyes regularly examined. In rare cases AMD can progress incredibly fast, i.e. weeks and/or months, resulting in permanent central vision blindness. It is imperative that AMD be caught as quickly as possible as earlier treatment usually results in less vision loss.

AMD is characterized by either 'dry' or 'wet'. Dry AMD occurs first; all people who have wet AMD have had the dry form of the condition. For 85-90% of people however, AMD will stay at the dry level and not progress to the advanced wet AMD. Dry AMD happens when light sensitive cells in the macula begin to break down; this causes gradual blurring of the central vision. As it progresses some individuals may see a blurry spot in the center of their vision. This loss of central vision increases as less of the macula can function. This can happen to either one eye or both; it is possible that both eyes may be affected at different times as well. For those who have AMD in one eye there is an increased likelihood that AMD will develop in the other eye. It is also possible to have AMD in both eyes and have the eyes progress to wet AMD at different interval.

A common early sign of dry AMD is drusen, which are yellow deposits located under the retina. Scientists are uncertain about the connection between drusen and AMD; what is known is that an increase in size and/or number of drusen raises the likelihood of developing into advanced dry AMD or wet AMD. Drusen alone does not cause vision loss, and many people can have a few small drusen in their eyes and not progress into AMD. However, people who have drusen should be regularly tested by their eye care professional in order to monitor this condition.

Wet AMD (also known as advanced AMD), occurs when abnormal blood vessels start to grow under the macula. These blood vessels are usually quite fragile and often leak blood and fluids, which raise the macula from its normal location at the back of the eye. This damage occurs rapidly, resulting in a greater loss of central vision. Wet AMD tends to be quite unpredictable and can appear very suddenly. There is no set schedule of when dry AMD changes into wet AMD; one of the early symptoms of wet AMD is the appearance of straight lines that are suddenly wavy. This, as well as any other vision change, should be reported immediately to your eye care professional as a comprehensive dilated eye exam is necessary.

There is currently no known cure for either dry or wet AMD. However, there are different treatments, depending on which type of AMD you have that can halt the progress of the condition. People who have the dry form of AMD can slow the progression and/or reduce vision loss by using specific high dose ocular vitamin therapy. As well, lifestyle changes such as quitting smoking and/or and improved diet can have a positive impact on reducing the chance/speed of progression of the disease. As well, vision should be monitored on a regular basis in order to track the progression.

Currently effective treatment is not available for all forms of wet AMD. Research is progressing, but at this date only 3 treatments for wet AMD have been approved by Health Canada. Although these treatments will not cure the condition, they can be very effective in halting the progression of wet AMD. They are:

Laser Photocoagulation (LPC): This method uses a high energy beam of light (laser) to destroy the fragile, leaky blood vessels. However, this method poses a risk of damaging surrounding healthy tissue as well as some vision. As well, there is a high risk of developing new blood vessels after this treatment; repeated treatments are usually necessary. Laser surgery is only used to treat a very small percentage of people who have wet AMD; it is usually most effective on those whose leaky blood vessels have developed away from the fovea (central part of the macula).

Photodynamic Therapy: This method involves injecting the drug verteporfin into an arm, which then travels throughout the body. This drug will 'stick' to the surface of new blood vessels; when a light is shined on the eye for 90 seconds the light will activate the drug, destroying the new blood vessels. It does not destroy the surrounding healthy tissues, but those who are being treated with this method must avoid any bright lights (indoor and outdoor) for five days after the treatment. It is a painless course of treatment that can be done in a doctor's office and usually takes 20 minutes. This treatment may need to be repeated as the results are often temporary.

Injections: This is the latest method to treat wet AMD and involves injecting drugs directly into the affected eye. Also known as anti-VEGF therapy, the injections work by blocking the growth of new abnormal blood vessels that tend to grow at an abnormally high level in eyes with wet AMD. Injections may need to be done as often as monthly. Successful injection treatments can help slow down vision loss; in some cases it can also improve vision. Injections may need to be done as often as on a monthly basis depending on the rate that the wet AMD is progressing. It is done in a doctor's office; the eye is numbed before injection and afterwards the eye will be monitored.

Research shows that AMD occurs more in people of white origin than those of African American descent. As well, women appear to be at greater risk for this disease than men. Having a family history of AMD can also increase the odds of having the condition. However, there are lifestyle choices that can either lessen the risk, and/or slow down AMD. Smoking has been linked to the increased risk of AMD; obesity has also been linked to the progression of early and intermediate stages of AMD to advanced AMD. Eating a healthy diet of fish and leafy green vegetables can reduce your risk of developing AMD; it is also important to maintain a healthy weight, exercise and maintain a normal blood pressure.

More information can be found about Age-related macular degeneration at AMD Canada, as well as the Canadian National Institute for the Blind.

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