What Causes Age-Related Macular Degeneration (AMD)?

Lylas G. Mogk, MD, a renowned expert on age-related macular degeneration (AMD), founding director of the Visual Rehabilitation and Research Center of Michigan, part of the Henry Ford Health System Eye Care Services, and co-author of Macular Degeneration: The Complete Guide to Saving and Maximizing Your Sight [1], explains:

AMD is currently understood to be caused by a combination of individual factors and environmental exposures.

Risk Factors for AMD

The four individual risk factors that predispose us to AMD that we cannot control are:

• advancing age
• Caucasian race
• a variation on a gene that regulates inflammation
• a family history of AMD

The individual risk factors that we can control include:

• smoking
• dietary habits
• unprotected sun exposure
• weight control/exercise
• blood pressure
• cholesterol

The environmental exposures that promote AMD and are not generally under our control include:

• smoke
• air pollution
• sunlight that is less modulated because of a thinner ozone layer
• insufficient nutrients in our food

Age and the environmental factors together produce an increased number of free radicals in the macula. Free radicals are unstable molecules that must be neutralized to keep them from causing damage. Mother Nature has provided anti-oxidants in food to neutralize these free radicals.

However, when we have too many free radicals and not enough anti-oxidants, damage is done. The first signs of damage in the macula are small whitish or yellowish spots called drusen, which the ophthalmologist can see usually before the individual is experiencing vision loss.

This initial damage triggers inflammation, which causes more damage, exacerbated by more free radicals. This results in more inflammation and the cycle continues, eventually scarring the macula and causing central vision loss.

More About Risk Factors

According to the American Academy of Ophthalmology, if you have at least two of the top five risk factors listed below, you should get a thorough eye examination by an ophthalmologist or other medical eye specialist and learn what you can do to reduce your risk for AMD ("Are You at Risk," 2010).

1. Smoking

Current smokers have a two-to-three times higher risk for developing AMD than people who have never smoked. Quitting smoking can reduce your risk of developing AMD (Thornton et al., 2005).

2. Obesity

Being overweight doubles the risk of developing advanced macular degeneration (van Leeuwen et al., 2003). Losing weight via a healthy diet and regular exercise can reduce your risk of developing MD.

3. Advancing Age

Although AMD may occur earlier, studies indicate that people over age 60 are at greater risk than those in younger age groups. For instance, a large study found that people in middle age have about a 2% risk of getting AMD, but this risk increased to nearly 30 percent in those over age 75 ("Facts About," 2009).

4. Hypertension

The National Eye Institute's Age-Related Eye Disease Study (AREDS) indicated that persons with hypertension were 1.5 times more likely to develop wet macular degeneration than persons without hypertension ("Facts About," 2009).

5. Family History of AMD

Studies indicate that your chances of developing AMD are 2.5 times higher if you have a parent, child, or sibling with macular degeneration (Fine, Berger, Maguire, & Ho, 2000). While not all types of macular degeneration are hereditary, certain genes have been strongly associated with a person's risk of AMD, and genetic predisposition may account for half the cases of AMD in this country (Haines et al., 2005).

Other Possible Risk Factors

Additional risk factors for AMD can include the following:

• Gender: Women appear to be more at risk for AMD than men ("Facts About," 2009).
• Race: Whites are much more likely to lose vision from AMD than are Blacks or African-Americans ("Facts About," 2009).
• Heart Disease: AMD is also linked to coronary heart disease ("Positive Trend," 2009).