Reducing the Risk for AMD
We have an opportunity to intervene in what may prove to be a major public health issue in the second half of this century: Age-related macular degeneration (AMD). There are four alterable risk factors to consider when discussing AMD with our patients and counseling them about prevention opportunities.
1. Quit Smoking
Studies show that cigarette smoking is a contributing factor in AMD. For patients at risk because of family history, light skin or eye pigmentation, smoking cessation messages are particularly important. For every one of my AMD patients, even for those in the earliest stages, I do a pack-year calculation (number of packs per day times the number of years of smoking). The larger the number, the greater the chance of vision loss from AMD. Every effort at smoking cessation for these patients will help reduce their risk of AMD.
A recent article (Evans et al, 2005) projected that 28,000 cases of vision loss from AMD in the United Kingdom were directly attributable to cigarette smoking. This convincing evidence can serve as recommendation material for our patients who still smoke.
2. Beware Blue Light Exposure
Patients should minimize their lifetime blue light exposure, which is cumulative, by sunglass protection against environmental light. While selective blue-light-absorbing lenses may be the ideal, they distort the color spectrum, which may handicap patients who have color-vision deficits.
Studies show that blue light plays a role in macular pigment degeneration. Fortunately, lutein- and/or zeaxanthine-pigment supplementation may replace those damaged retinal pigments. We should offer our patient these protective strategies at the earliest age possible.
3. Watch Your Cholesterol
A high-lipid diet may also contribute to AMD. Many patients over the age of 60 already take statin drugs to lower cholesterol and so have their levels under control. For those undiagnosed or suspected because of the presence of corneal arcus, for example, recommend them for appropriate evaluation.
4. Take Your Supplements
Finally, antioxidant and vitamin/mineral supplements have emerged as a potential treatment for atrophic AMD. The initial report from more than 15 years ago suggested that zinc supplementation stabilized AMD. That, and other factors, led to the age-related eye disease study (AREDS), which had four treatment arms: Placebo, zinc plus copper, antioxidant vitamins (A, C, beta carotene) and combination vitamin and mineral supplementation. The bottom-line outcome was that the combination group demonstrated about a 25 percent risk reduction compared to the placebo group. The effect was most pronounced in patients who had moderately advanced disease.
What about Lutein? One criticism of AREDS was that it didn't include lutein, which at the time hadn't achieved scientific standing. Since then, studies have shown that both lutein and zeaxanthine, when taken orally, will show up in the blood stream and can be measured in the macula. On the drawing board is AREDS II, which will look at previous subjects, substituting lutein for beta carotene among the smokers and reducing the amount of zinc recommended.
Final Word Where does that leave us regarding vitamin and mineral supplementation advice? Antioxidant vitamins and minerals (zinc and copper) together with lutein and/or zeaxanthine seem to represent the foundation of a recommendation for patients at risk for AMD. Advise caution with regard to beta carotene for patients who will continue to smoke.
For references, visit www.clspectrum.com/references.asp and click on document #117.
Dr. Semes is an associate professor at the University of Alabama at Birmingham School of Optometry.