Age-related macular degeneration (AMD) of the eye occurs when the cells of the macula - an irregular yellow depression on the center of the retina - becomes damaged and stops functioning.
The retina is a thin layer of light-sensitive tissue that stretches across the back of the eye. It contains rod cells for night vision and seeing movement, and cone cells for light and colour vision. The retina functions like a screen onto which all visual images are projected.
The macula (which contains no rods) is the most sensitive part of the retina, and its role is to view complex images: it allows us to focus on objects directly in front of us; enables us to see fine detail during activities such as reading, writing, sewing and driving; and determines our capacity to distinguish colour.
Most authorities agree that macular degeneration is most common with advancing age (usually after 60) and is the result of free-radical damage to the eye (Proc Natl Acad Sci USA, 2002; 99: 14682-7). While there appears to be no cure for the condition, there are several ways you can help prevent it.
* Boost antioxidants. Many antioxidant vitamins, including A, C and E, but also selenium, can help prevent AMD (Am J Epidemiol, 1988; 128: 700-10; Arch Ophthalmol, 1993; 111: 104-9). Increase your intake of vitamin A-rich fruits and vegetables (carrots, pumpkin, squashes) and vitamin C-rich foods (dark-green leafy vegetables and citrus fruits).
* Eat your tomatoes. One study noted that low levels of lycopene (an antioxidant found in tomatoes) were most strongly linked to the development of AMD (Arch Ophthalmol, 1995; 113: 1518-23). Lycopene is found in rich supply in processed tomato products, such as tomato paste, ketchup and tinned tomatoes.
* Lose weight. There is evidence that women who are overweight may have trouble metabolising the eye-protective carotenoids lutein and zeaxanthin (see box, lower right) or metabolise them more slowly (Am J Clin Nutr, 2000; 71: 1555-62).
* Quit smoking. Smoking has been linked to macular degeneration. Stopping smoking may reduce the risk of developing macular degeneration (JAMA, 1996; 276: 1141-6).
* Eat more fish. Eating fish more than once a week can halve your risk of developing AMD vs those who only eat fish once a month (Arch Ophthalmol, 2000; 118: 401-4).
* Be choosey about alcohol. Total alcohol consumption has not been linked to AMD (Am J Ophthalmol, 1996; 122: 743-5; Ann Epidemiol, 1999; 9: 172-7). But specific types of alcohol may have different effects. Beer, for instance, has been linked to an increased risk of AMD (Ophthalmology, 1998; 105: 789-94; Am J Ophthalmol, 1995; 120: 190-6), while wine drinkers were found to have a significantly lower risk of macular degeneration compared with those not drinking wine (J Am Geriatr Soc, 1998; 46: 1-7; Am J Ophthalmol, 1995; 120: 190-6). Red grape juice may produce the same benefits without the risks of alcohol.
* Wear sunglasses. Bright sunlight can trigger oxidative damage in the eye which, in turn, can cause macular degeneration (Surv Ophthalmol, 1988; 32: 252-69).
* Protect your eyes from electromagnetic fields. There is emerging evidence that eyes are very sensitive to EMF radiation. Limit the time spent on your computer or take frequent breaks. Swap metal frames (which act like antennae, concentrating EMFs around your eyes) for plastic ones, and take your glasses off when using a mobile phone.
* Zinc might work. There is some evidence that zinc supplementation may slow the progression of AMD (Arch Ophthalmol, 1988; 106: 192-8), although there is other evidence that it doesn't work (Invest Ophthalmol Vis Sci, 1996; 37: 1225-35). Before supplementing, it may be worth getting yourself tested for zinc deficiency.
* Is it something else? Certain underlying diseases, such as diabetes and high blood pressure, can lead to AMD-like symptoms. When these are treated, often the impaired vision improves and degeneration of the macula can be avoided.