Macular Disease – Focusing on the Right Lifestyle
Age-related macular degeneration (AMD) of the eye occurs when the cells of the macula – an irregular yellow depression on the centre 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.
Sidebar: Helpful Herbs
Bilberry (Vaccinium myrtillus), a type of blueberry, contains active flavonoid compounds known as anthocyanosides, which act as antioxidants in the retina of the eye. Over-the-counter bilberry supplements are usually standardised to 25 per cent anthocyanidins, but you may also benefit from a range of other bilberry preparations. In WWII British folklore, for example, RAF pilots used to eat bilberrry jam to improve their vision.
Later studies show that bilberries do indeed improve vision (Minerva Oftalmol, 1979; 21: 283-5; Ann Ottalmol Clin Ocul, 1966; 92: 595-607), protect against cataracts (Ann Ottalmol Clin Ocul, 1989; 115: 109), improve blood flow throughout the tiniest vessels in the body (Gazz Med Ital, 1980; 139: 485-91; Minerva Cardioangiol, 1978; 25: 255-76) and may reduce inflammation.
Try taking 480-600 mg per day of an extract standardised to 25 per cent anthocyanosides, in capsules or tablets.
Ginkgo biloba may help treat early-stage macular degeneration (Presse Med, 1986; 15: 1556-8), although published studies are few and far between. Many healthcare professionals recommend 120-240 mg/day of a standardised extract (24 per cent Ginkgo flavone glycosides and 6 per cent terpene lactones) in capsules or tablets.
Sidebar: An Antioxidant Double Act
There is copious evidence for the role of two particular antioxidants – lutein and zeaxanthin – in maintaining eye health. Carotenoid composition varies between internal organs, suggesting selective uptake or metabolism of these nutrients. These two are the only carotenoids found in the eye. Recent research suggests that the body absorbs and then deposits lutein in two different parts of the eye – the macula (the bright yellow spot at the centre of the retina) and the lens.
Evidence suggests that supplementation with lutein and zeaxanthin can help retard the process of age-related macular degeneration, or AMD (Am J Clin Nutr, 1995; 62 [6 Suppl]: 1448S-61S). In one study, the incidence and severity of AMD was reduced by 43 per cent through supplementation (JAMA, 1994; 272: 1413-20).
Lutein and zeaxanthin are abundant in a wide range of foods, including mango, papaya, oranges, peaches, kiwi, spinach, squash, peas, lima beans, green beans, broccoli, brussels sprouts, cabbage, kale, lettuce, prunes, pumpkin, sweet potato and honeydew melon. One study found that changes in diet – for instance, adding corn and spinach – not only elevated levels of lutein and zeaxanthin, but also improved the density of the macular pigment (Invest Ophthalmol Vis Sci, 1997; 38: 1795-801).
- This article first appeared in the May 2003 (volume 14 number 2) edition of What Doctors Don’t Tell You
