Cure elusive for age-related macular degeneration
But seniors can stay happy, independent
Dr. Zoe Oliver recently met Marion*, an 83-yearold woman who had fallen down the basement stairs on her way to do laundry and had broken her hip. Marion said that she had looked down to see where she was going, but “just hadn’t seen the first step.” Her doctor had diagnosed her with macular degeneration years prior, and her visual impairment had steadily worsened. Daily activities like watching TV or preparing food were becoming nearly impossible. And now, she had sustained a serious injury related to her difficulties with sight.
Age-related macular degeneration (AMD) is the leading cause of visual impairment in Canada; more than 13 per cent of people over 84 years of age suffer from the disease. The macula is an important area at the back of the eye, responsible for what we see in the centre of our vision. With age, the macula can deteriorate, causing the central vision to be blurry, or completely absent.
The macula is made up of little spots of yellowish pigments called carotenoids, which affect how we see colours. Many proposed treatments for AMD target the health of these carote- noids at the back of the eye. Carotenoids occur naturally in food, as well; they make carrots orange and spinach green.
When we can’t see what is in front of us, certain daily functions can become very challenging, or even hazardous. Those with AMD sometimes have to give up driving, and can become increasingly reliant on others to help with the chores of life.
Falls and fractures (like in Marion’s case) become more frequent, as does depression and social isolation. Added up, these struggles can make it too difficult for some elderly to live alone, and those with AMD enter personal care homes on average three years earlier than the rest of the population.
You can understand how someone faced with these prospects might be keen to try any and all therapies available. Unfortunately, effective treatments have been elusive. A combination of vitamins and supplements is often prescribed in an attempt to stall the progression of AMD. The idea is that these vitamins will act like janitors at the back of the eyeball, sweeping up any debris and repairing minor defects in the carotenoids that occur over time. Other supplements have been studied as well, such as ginkgo biloba and omega 3s.
But do these supplements actually work? And what might be the potential downside of these therapies?
The Age-Related Eye Disease Studies (AREDS 1 and 2) are the most important research trials looking at the role of dietary supplements in supporting the pigments of the eye. AREDS 1 was conducted by the National Eye Institute in the U.S. and reported in 2001. It showed that a formulation of dietary antioxidants and zinc (consisting of vitamin C 500mg, vitamin E 400 IU, carotene 15mg, zinc 80mg and copper 2mg) was associated with a small, but important, reduction in the risk of vision decline from AMD.
AREDS 2 was recently published in the Journal of the American Medical Association and looked at whether the addition of novel carotenoids could improve on the AREDS 1 formulation. In this six-year study involving more than 4,000 study subjects, investigators tested whether adding the carotenoids lutein and zeaxanthin to the AREDS 1 mix could slow AMD progression. The study also looked at whether adding omega-3 fatty acids might be beneficial. The researchers hypothesized that these carotenoids and omega-3 fatty acids might protect vision, a suggestion supported by animal studies and other scientific knowledge.
The results of AREDS 2 were informative, but disappointing. None of the supplements tested produced an effect. However, what we did learn echoed some previous studies, which is that beta-carotene promotes the development of lung cancer, especially in former smokers.
Despite a multitude of studies involving thousands of subjects, we have yet to discover any pill that will definitively cure AMD. And while we have looked primarily at the AREDS studies, it should be noted that the smattering of other studies on AMD and supplements have been largely negative, failing to show any benefit at all.
However, we now know that current vision-protecting formulations should be updated by having the beta-carotene component replaced with the newer and safer carotenoids, like lutein and zeaxanthin, especially in those individuals with early AMD who are current or previous tobacco users.
For the right patient, budget permitting, the AREDS supplements may produce small positive effects. But it’s important to mention that significant amounts of these carotenoids can be obtained by simply eating dark, leafy greens like kale and broccoli.
And as with any cause of visual impairment, those with AMD should consider modifying their living environment to prevent falls, increase quality of life, and preserve independence for as long as possible.
NOTE: Identifying details have been changed to preserve confidentiality.