Age-related macular degeneration (AMD)

By Elizabeth Hartland

The macula, a small central area of the retina situated at the back of the eye, is responsible for central vision i.e. for reading, writing, watching TV, recognising faces, driving and doing any fine work.

Degeneration of the macula is the leading cause of severe loss of vision and blindness in people over the age of 50. It is a slow progressive, painless and irreversible condition affecting an estimated 10% of the total population and as many as 600,000 people in the UK. Prevention and treatment at an early stage of development is vital.

What is macular degeneration?

The macula gets most of its nourishment from blood vessels in a deeper layer which is separated from the macula by a membrane. When the membrane becomes damaged, the macula does not function properly. If the membrane breaks down, new abnormal blood vessels form to try to repair the damage but can bleed and displace the macula.

What signs and symptoms may alert someone of the onset of AMD?

As the cells of the macula deteriorate, a loss of central visual sharpness will occur. Straight objects such as the edge of a door may appear bent. Other objects may appear to change shape, size or colour, and seem to disappear. Vision can become blurry, lines may become distorted and dark spots may appear in the centre of the field of vision. Such visual symptoms will eventually lead to difficulty in reading, carrying out close work or driving.

As the condition progresses, the central area of vision becomes totally blocked by a circular area of blindness, whilst the peripheral (side) vision is spared. This allows, for example, a sufferer to see the outline of a head but have difficulty making out the facial features or, when reading, several words may be blocked out. Sufferers will often learn to make the most of their remaining vision.

The progression of the condition will vary, with many sufferers seeing little or no change over a number of years, whereas in others there is a slow progressive loss of the central vision.

In some cases, only one eye is affected and the other continues to see well for many years.

Occasionally, there can be a sudden loss of the central vision due to a leakage from tiny blood vessels under the macula. This is known as disciform macular degeneration. In this situation a larger area of the central vision can be affected as the area heals to form a scar.

How can AMD be detected?

The Amsler grid test can be used to detect early loss of vision associated with macular degeneration. This involves looking at a square grid made up of criss cross lines with a dot in the centre. The grid is held 12 inches (around 30cms) from the face and reading spectacles are used if appropriate. The lines on the grid should all be straight and continuous. If the lines are wavy, distorted or blurred, or if there are missing or broken areas on the grid, then the significance of this should be discussed with the optician at an early stage. Early evaluation, especially in those with a family history of AMD, is important because laser treatment, if it is suitable, is only effective in the early stages of the condition.

Should the presence of leaking blood vessels under the macula be suspected, a fluorescein (or indocyanine green) angiogram may be carried out. This involves the dilation of the pupils using drops followed by an injection of a dye into a blood vessel in the arm. The dye circulates throughout the body and, as it passes through the eye, photographs of the blood vessels at the back of the eye are taken. This will show up abnormal or leaking blood vessels under the macula.

What are the causes of AMD?

Whilst age is often cited as the main risk factor for developing AMD, diet, smoking, atherosclerosis, sun exposure and genetics can also influence the development of the disease.

• Diet and nutrition. The macula’s fragile cells are highly susceptible to damage from free radicals. Research indicates that people with a low dietary intake of antioxidants may be at increased risk of developing AMD.

• Smoking reduces protective antioxidants in the eye. AMD is more than twice as common in people who smoke more than one packet of cigarettes a day compared to people who do not smoke.

• Atheroscerosis in the small arteries of the retina can impair the blood supplying vital nutrients to this part of the eye.

• Sun exposure. The cells of the macula are highly sensitive to sunlight. Excess exposure to the sun can lead in time to deterioration of the macula.

• Genes. Some studies show that AMD may be, in part, inherited. An individual may, therefore, be at higher risk of developing AMD if they have one or more immediate relatives with the condition.

Diet and lifestyles recommendations

Whilst prevention or treatment at an early stage of development is vital, improving the diet may help to enhance overall vision, reduce blurriness and slow deterioration from AMD. The following recommendations are designed to help improve circulation and support the immune system.

• Fruits & vegetables are rich in antioxidant nutrients important for immune and cardiovascular support: include lots of colourful, fresh vegetables (four portions daily) and fruit (three pieces daily) – include those especially rich in the carotenoids lutein, zeaxanthin and lycopene such as dark green leafy vegetables (spinach, kale, broccoli) corn, potatoes, carrots, peas, tomatoes, kiwi, and oranges. Lutein and zeaxanthin, the pigments that give fruits and vegetables their colour, are concentrated in the very part of the retina which is affected by degeneration. These two carotenoids are the only pigments found in the macula. By contrast, beta-carotene, which has often been seen as ‘the eye carotenoid’, is virtually absent in the eye.

• Increase berry consumption i.e. bilberries, cranberries, blackcurrants and blueberries – these are especially rich in the antioxidants known as flavonoids. Such antioxidants have been shown to speed up the production of rhodopsin – a purple pigment found in the retina which is critical to the eye’s adaptation to light. They can also help to strengthen capillaries and reduce haemorrhaging in the retina.

• Adequate protein helps collagen formation. Include organic chicken, oily fish such as salmon, sardines, mackerel, tuna, tofu and quorn. Red meat contains saturated fat, therefore should be avoided.

• Avoid all stimulants including coffee, tea, chocolate and sugar.

• Avoid foods that contain refined carbohydrates, including sugar, biscuits, cakes, puddings, pastries, sugared breakfast cereal, carbonated drinks, chocolate, and other confectionery, ice cream, jams, processed and canned foods.

• Avoid alcoholic drinks.

• Avoid foods with added salt.

• Avoid foods that are high in saturated fats like red meat, dairy products and fried foods. When preparing foods, grill, bake or stir fry with olive oil, and use flax on salads and vegetables.

• Reduce dairy produce including milk, cheese, yoghurt and some sauces Introduce soya, nut and rice milk, soya yoghurt and goats cheese as alternatives.

• Use nuts and seeds as snacks in-between meals or add to breakfast cereals and salads i.e. Brazil nuts, walnuts, almonds, hazelnuts, sunflower, sesame, pumpkin. Have three portions of oily fish (herring, pilchards, sardines) every week. These foods contain essential fatty acids (beneficial to the whole vascular system including the vessels supplying the eyes) and nutrients (especially the mineral zinc) important for immune function and circulation.

• Drink plenty of bottled or filtered water every day.

• Avoid smoking and smoky atmospheres.

• Wear sunglasses and brimmed hats to help reduce exposure of your eyes to the sun.

• Exercise: this helps improve circulation bringing oxygenated blood to the body including the eyes.

• Give your eyes enough rest. Avoid straining with dim light. Use full spectrum light bulbs for light during the day and evening

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Elizabeth Hartland has a Bachelor of Science Degree in nutrition, together with a Diploma from the Institute of Nutritional Therapy. She is married with two young children and has a passion for good nutrition and helping others to find better health. 282 427 652