Update on Macular Degeneration
Results from the Age-Related Eye Disease Study 2 and Beyond.
By A.Paul Chous, MA, OD, FAAO
Results of the long-awaited Age-Related Eye Disease Study 2 (AREDS2) were presented May 5TH in Seattle during the most important eye research meeting in the world, Association for Research in Vision and Ophthalmology (AVRO). I was fortunate enough to attend this special session, which was also broadcast live on the Internet to eye doctors and vision researchers all over the globe. The original AREDS study examined the potential benefits of an antioxidant multivitamin (vitamins C, E, and beta-carotene), plus zinc for people with various degress of age-related macular degeneration (AMD).
AMD is the leading cause of severe vision loss and legal blindness in the developed world, and accounts for 50% of all legal blindness in the US. The original AREDS was published in 2001 and showed that people with so-called "intermediate" AMD (definite abnormalities in the macula, the center of the eye's light sensitive retina at the back of the eye, but no significant vision loss) were about 25% less likely to progress to "advanced" macular degeneration with significant vision loss. The AREDS formula did not benefit patients with mild AMD. Secondary analysis of AREDS (done years later) showed that eating a higher glycemic index diet also increased the risk of advanced AMD.
AREDS 2 built upon these findings by testing various combinations of the plant pigments lutein and zeaxanthin (see my last dLife column, Macular Pigment and Diabetes), as well as beta-carotene (found in plants like carrots) and omega-3 fatty acids (found in fish). This time, only patients with "intermediate" AMD were tested. The researchers found that substituting lutein and zeaxanthin for beta-carotene resulted in lower risk of progressing to "advanced" AMD and significant vision loss than the original AREDS formula, especially for people who had lower blood levels of lutein and zeaxanthin to begin with (this is about half of all Americans). In addition, omega-3 fatty acids appeared to have no significant benefit on reducing risk of progression and vision loss, even though previous research has suggested benefit. Finally, patients who took beta-carotene and had previously smoked were found to have twice the risk of being diagnosed with lung cancer during the study.
Yes, I know — even eye doctors were confused by the complexity of these findings! And there is on-going debate about what to make of all this. Here is my take on the results of this new study:
1. These results will be analyzed a hundred different ways — by looking at patient characteristics such as body weight, diet, genetics, and smoking status — over the next 5-10 years, so it's impossible at this point to know all the pearls of wisdom lying in the raw data of the study.
2. Individual patients with "intermediate" AMD need to be told this by their eye doctors, and need to be taking an eye vitamin that evidence shows is most likely to benefit them — the original AREDS formula without beta-carotene and with lutein and zeaxanthin. The possible benefits of fish oil need to be studied further.
3. We already knew, long before AREDS and AREDS2, that smoking cigarettes dramatically increases the risk of advanced AMD, permanent vision loss, and legal blindness (3 to 34 times increased risk depending on your genes!), so the best thing any person can do is never smoke or quit smoking immediately to avoid this very serious eye disease. Furthermore, any patient who has smoked regularly now or in the past should almost certainly not take beta-carotene supplements.
4. AREDS2 did not study patients with early AMD, so we don't know if these eye vitamin recommendations will benefit them or not. However, there is increasing evidence that diets high in lutein and zeaxanthin (found in dark green leafy vegetables — especially kale, egg yolks, and orange peppers), as well as evidence that taking supplemental lutein and zeaxanthin, not only lowers the risk of developing any AMD but also improves vision in people with early AMD. Moreover, diets higher in refined carbohydrates (cookies, crackers, pastries, high glycemic index beverages — including soda and fruit juice) are more likely to develop AMD and advanced AMD.
5. People with diabetes are no more or less likely to develop AMD than other people, but once we do develop AMD, it is more likely to progress faster than in people without diabetes. Eating a diet with less refined carbohydrate, eating more dark green, leafy vegetables, and taking supplemental lutein and zeaxanthin will likely reduce our risk of developing AMD.
For more information on diabetic eye disease, consult Dr. Chous' book Diabetic Eye Disease: Lessons From a Diabetic Eye Doctor, Fairwood Press, Seattle, 2003.
NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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