Age Related Macular
Degeneration (AMD)
Age related macular degeneration (AMD)
is one of the most common causes of poor vision after age 60. AMD is a
deterioration or breakdown of the macula. The macula is a small area at
the center of the retina in the back of the eye that allows us to see
fine details clearly and perform activities such as reading and driving.
The visual symptoms of AMD involve loss of central vision. While peripheral
(side) vision is unaffected, one loses the sharp, straight-ahead vision
necessary for driving, reading, recognizing faces, and looking at detail.
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Although the specific cause is unknown, AMD
seems to be part of aging. While age is the most significant risk factor
for developing AMD, heredity, blue eyes, high blood pressure, cardiovascular
disease, and smoking have also been identified as risk factors. AMD
accounts for 90 percent of new legal blindness in the US.
Nine out of 10 people who have AMD have the dry form (called atrophic), which results
in thinning of the macula. Dry AMD takes many years to develop. Currently
there is no treatment for this form of AMD.
The wet form of AMD (called exudative)
is less common (occurring in one out of 10 people with AMD), but is
more serious. In the wet form of AMD, abnormal blood vessels may grow
in a layer beneath the retina, leaking fluid and blood and creating
distortion or a large blind spot in the center of your vision. If the
blood vessels are not growing directly beneath the macula, laser surgery
is the only proven effective treatment, to date, for wet AMD. The procedure
usually does not improve vision but prevents further loss of vision.
For those wet AMD patients whose blood vessels are growing directly
under the center of the macula, a procedure called photodynamic therapy
(PDT) may be used to treat some patients with fewer visual side effects
than other treatments.
Most recently, in December of 2004, the FDA approved Macugen® (pegaptanib sodium injection) for the treatment of the ‘wet’ form of age-related macular degeneration. Macugen®, works by blocking vascular endothelial growth factor (VEGF), a protein that promotes blood vessel growth. This treatment has the potential for helping all patients with the wet form of the disease, whereas the currently approved treatments (photodynamic therapy and laser photocoagulation) are only approved for patients that have a subtype of wet macular degeneration. According to the data collected during the clinical trials, patients receiving Macugen® were less likely to progress to legal blindness and experience severe vision loss. Macugen® is injected into the vitreous portion of the eye (the clear jelly-like substance that fills the eye from the lens back to the retina). Due to the fact that the production of VEGF is ongoing, routine administration of this drug is required.
Promising AMD research is being done on many fronts. In the meantime,
high-intensity reading lamps, magnifiers and other low-vision aids help
people with AMD make the most of their remaining vision.
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