What’s new in AMD?
Age-related macular degeneration – or AMD – is the leading cause of blindness in Canada. It’s a disease that can develop and progress unnoticed for years, partly because there’s no physical pain and symptoms are slow to show themselves. There are two kinds of AMD – wet and dry. “Of all people with AMD, about 85 per cent have dry AMD,” says Dr. Tom Sheidow of the Ivey Eye Institute at the University of Western Ontario. “However, wet AMD causes about 90 per cent of vision loss.”
Right now, there is no cure for either wet or dry AMD but there are treatment options for both. For dry AMD, specific antioxidant vitamin therapy is the only treatment proven to slow disease progression. Patients will also benefit from lifestyle changes, such as quitting smoking, eating a balanced diet, losing weight, keeping hypertension under control and avoiding excess exposure to sunlight.
Unfortunately, those with dry AMD can slowly lose their vision over several years and a significant number will go on to develop wet AMD.
What is wet AMD?
Wet AMD involves the growth of new and abnormal blood vessels under the retina called choroidal neovascularization, or CNV. “These vessels begin to grow under the retina and then push their way up through it, leaking blood and other fluids as they go,” says Dr. Sheidow. It’s this leakage and the disruption or bulge on the retina that causes the distortion and blind spots familiar to those with wet AMD. Fortunately, there are more effective treatment options available for this form of the disease and science continues to make significant progress developing new ones.
Early treatments for wet AMD
Early treatments such as thermal laser photocoagulation and later, photodynamic therapy (PDT), targeted the bleeding from the CNV in an effort to rid the macula of the fluids that interfered with its normal function. Unfortunately, photocoagulation also caused additional vision loss in the surrounding retina and retreatment was often necessary. PDT uses a cool laser and a photosynthesizing drug, is more effective and has the added benefit of not harming the surrounding retina. “Most patients stabilize after a full course of PDT,” says Dr. Sheidow. “On the downside, however, less than 10 per cent of PDT patients experience an actual improvement in vision.”
Latest in wet AMD treatment
Missing from the earlier treatment outcomes was any significant increase in vision. Recent treatments may overcome this, especially with the introduction of the latest in the class of anti-vascular endothelial growth factor drugs (anti-VEGF). Lucentis is the most recently approved anti-VEGF and was designed specifically for the eye so it can penetrate the retina quickly and completely to reach the area of abnormal blood vessel growth. And for the first time, studies showed it resulted in an average visual gain for patients.
Lucentis therapy acts on the source of wet AMD. VEGF plays an important role in regulating and managing the growth of blood vessels throughout the body. In an eye with wet AMD, VEGF-A and its many permutations stimulates the overproduction of new and abnormal blood vessels. Lucentis was specifically designed to block the action of all VEGF-A permutations, leading to a cessation of blood vessel growth and a reduction of leakage and bleeding.
“All current forms of anti-VEGF therapy require injection into the eye to be effective. And these injections are continued until the physician feels the blood vessels are controlled,” says Dr. Sheidow. With the new therapies available, Dr. Sheidow says there’s “significant interest” in combination therapy. “The goal is to use the unique aspects of each drug, pairing them with a drug of a different type in an effort to enable each drug to work better,” says Dr. Sheidow.
Since early detection is the key to successful AMD treatment, it’s important to be aware of any changes to your vision. A simple eye test using an Amsler grid can be done at home. “No therapy can be implemented until you make your eyecare professional aware of changes in your vision,” says Dr. Sheidow. The best way to accomplish this is with regular visits to your eye doctor.