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The Globe and Mail

New drugs saving vision of patients with AMD


Question: I suffer from macular degeneration. There recently have been numerous news stories about new treatments for this condition. Can any of these new treatments really help save my eyesight?

Answer: If you are over the age of 50 and find your vision is blurred or distorted, you should know about age-related macular degeneration (AMD), a common eye disease that can make many daily activities increasingly difficult. The good news is that there are many treatments available, and others in development, to combat the loss of vision and help maintain your eyesight.

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AMD affects more than two million Canadians, causing deterioration of the macula -- an area at the back of the eye in the centre of the retina which is responsible for fine-focused visual tasks such as reading, driving and recognizing faces.

It is a serious and often devastating disease, and diagnosing it early is crucial to determining an appropriate treatment and improving the quality of life of patients. It is therefore important to consult your physician if you experience any signs of blurriness or distortion in your vision.

There are two types of AMD: dry and wet. Dry AMD is most common and affects 85 per cent of AMD patients.

AMD usually develops as the dry type and starts with a failure of the deepest layer of pigmented cells in the retina to clean out byproducts produced by nearby cell layers. Over many years, this process eventually leads to the inability of the cells to function properly.

Symptoms include long periods of stable vision interspersed with shorter periods of further deterioration of eyesight. Vision loss tends to be gradual, and people are often not aware that they suffer from AMD until it becomes more advanced.

Dry AMD should be closely monitored and assessed by a retina specialist if there are significant changes. You can treat moderate dry AMD and help retain vision by maintaining a vegetable-rich diet, reducing fat intake, using ultraviolet light protection, such as wrap-around sunglasses, and taking special vitamins rich in antioxidants and zinc.

Dry AMD can sometimes progress to wet AMD, when not enough oxygen reaches the retina. Essentially, the eye begins to produce abnormal new blood vessels beneath the retina. These vessels leak fluid and blood, which can scar the macula and cause rapid vision loss over weeks or months.

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Treating wet AMD can be more challenging than dry AMD, and often requires numerous treatments, because the abnormal blood vessels tend to grow back.

If the abnormal blood vessels lie outside the centre of the macula, thermal laser therapy can be used to destroy them using heat.

If, however, the abnormal blood vessels lie beneath the central macula, patients may be treated with photodynamic therapy (PDT) and Visudyne to stabilize their vision. Visudyne is a drug that is injected intravenously, and is absorbed by the abnormal blood vessels in the back of the eye. A cold laser is then shone onto the affected area, activating the drug and producing a reaction that destroys the abnormal vessels. Since the abnormal blood vessels tend to grow back, multiple treatments are often required.

Another proven treatment option is Macugen. It is a drug that is injected directly into the eye and works by stopping new blood vessels from growing. Macugen has shown a 70-per-cent success rate in preventing moderate vision loss caused by wet AMD, but requires injections every six weeks for two years or longer.

Lucentis is the newest drug to be proven successful in treating wet AMD. It is also injected into the eye to stop new blood-vessel growth beneath the retina. Clinical trials in the United States have demonstrated that approximately 95 per cent of treated patients maintained or gained vision. Lucentis has been approved for sale in the United States by the Food and Drug Administration, but is not yet approved for use in Canada. It is, however, an exciting alternative, and given its overwhelming success in clinical trials worldwide, I am hopeful that this new drug will be fast-tracked for approval here in Canada.

Avastin, which is similar to Lucentis, has been approved in Canada for the treatment of colorectal cancer, and has also shown promising results in the treatment of wet AMD. Pilot studies have demonstrated that it can maintain and even improve vision, and formal trials will begin shortly. In the meantime, it is available here as a colorectal cancer treatment, and can be used on an experimental basis for treating wet AMD.

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Meanwhile, one of the most exciting concepts in treating wet AMD is the use of combination therapy. One drug, such as Visudyne, is used to close the abnormal blood vessels, while another, such as Macugen, Lucentis or Avastin is used to prevent the vessels from growing back. Triamcinolone, a form of cortisone, can also be used in combination therapy. It reduces inflammation and blocks the regrowth of blood vessels. When used alongside PDT, these drugs can reduce the number of treatments needed to stabilize the retina, and can improve visual outcomes. Combination therapies like this are in their early stages of study, but have proven very promising.

Dr. Michael Brent is a retina specialist at Mount Sinai Hospital, Toronto Western Hospital and the University Health Network in Toronto.

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