Age-related macular degeneration (AMD) Dr Rob Hicks AMD is the commonest cause of blindness in the UK. We explain the differences between wet and dry AMD, their causes and treatments, and how to minimise your risk.

In this article

What is it? What causes it? What are the symptoms?

Who's affected? What's the treatment?

Can it be prevented? Advice and support

The macula is located at the back of the eye at the centre of the retina. It enables us to see fine detail and objects directly in front of us. It plays a vital role in helping people to read, write, drive and perform other detailed tasks. It also enables us to recognise faces and see colour.

There are two types of AMD:

Dry AMD is the most common form of the condition. Cells in the retina fail to function properly as a person gets older. The cells don't take in enough vital nutrients and fail to clear by-products of cell functioning. This causes tiny abnormal deposits, called drusen, to be left under the retina, making it uneven.

In time, retinal cells degenerate and die causing sight loss. This occurs very gradually over many years.

Wet AMD accounts for 10 to 15 per cent of cases. It often develops quickly and is also known as 'neovascular AMD' because it involves the growth of new blood vessels behind the retina.

These new blood vessels are very fragile and so may leak fluid or blood. This results in scarring that causes rapid visual loss.

It's unclear what causes AMD. It becomes more likely as a person ages because, over time, the cells in the macula become damaged and worn out.

Both eyes are usually affected, although one eye may be affected before the other. The good eye usually compensates for the affected eye and for many years this can disguise the fact that there’s a problem. There's no pain or redness of the eyes.

Because it's central vision that's affected, patients retain some residual vision, but this is at the periphery of their field of vision where images aren't in focus.

Any activity that requires detailed, clear vision is compromised, and in the late stages of the disease sight loss is so severe that patients are offered registration as partially sighted or blind.

In developed countries it’s estimated that one in 50 people over 50 years of age, and up to one in five people over the age of 85 have AMD.

A person is at greater risk of developing AMD if they smoke, have high blood pressure, or someone in the family has the condition.

Currently, there's no reliably proven medical treatment for dry AMD. However, not smoking and eating a healthy diet may help to slow the rate of deterioration. High does of beta-carotene, vitamins C and E, and zinc may help to slow down visual loss for some people who already have AMD.

There has been particular interest recently in two carotenoid dietary substances known as lutein and zeaxanthin, which in some cases seem to reduce the development and progression of AMD. Although there are not yet any studies to consistently demonstrate a benefit, people at high risk of AMD may want to check their intake of these substances.

Additional lighting and magnifiers can help those with dry AMD to make better use of their residual sight.

Medical breakthroughs in the treatment of wet AMD mean that, in most cases, treatments can prevent further visual loss, and in some cases restore partial sight.

There are three types of treatment for wet AMD:

• Photocoagulation uses a hot laser to seal leaking blood vessels, but can only be used in a minority of cases where the leakage is not directly in the centre of the macula.
• Photodynamic therapy (PDT) uses a cold laser to seal leaking blood vessels. This involves injecting a drug that reaches and coats the abnormal blood vessels via the blood stream. The drug is then activated by shining a light at the coated blood vessels and it destroys them.
• Anti-vascular endothelial growth factor (anti-VEGF) treatments target a protein involved in the formation of new blood vessels. High levels of VEGF can cause proliferation of blood vessels and fluid leakage. The drugs are injected under the macula. The number of injections varies. In trials the injections were given either every four or every six weeks, but in practice clinicians have to decide on the most appropriate treatment regime based on their assessment of the patient's response to the drugs. Anti-VEGF treatments have been shown to halt sight loss and in some cases restore it.

A new drug treatment for wet AMD, called anecortave acetate, aims to stop new blood vessels forming, but is injected behind the eye rather than into it. Currently, it's only at the experimental stage.

Apart from the growing risk as people age, there appears to be a genetic influence that significantly increases the risk of developing AMD, particularly if other risk factors are present. While ageing and genetic predisposition can't be modified, other risk factors can.

Smoking - people who smoke at least double their risk of developing AMD. The risk may be as high as 34 times that of a non-smoker if there's also a family history of AMD.

When people stop smoking the risk decreases, but this can take up to 20 years so it's important not to start.

Ultraviolet (UV) light - although it's thought that UV light doesn't reach the retina, and so doesn't increase the risk of developing AMD, wearing high-quality sunglasses in bright sunlight is recommended to protect eye health generally.

Nutrition - the role of vitamins and minerals and antioxidants in helping to prevent AMD isn't clear. Some scientific evidence suggests a diet rich in antioxidant vitamins and minerals, including lutein and zeaxanthin may help reduce the risk of a person developing AMD, although other studies suggest the scientific evidence isn't yet strong enough to recommend this.

However, a diet rich in antioxidant vitamins and minerals is unlikely to cause any harm. It makes sense to eat plenty of fruit and vegetables each day, particularly leafy green vegetables (the best sources of lutein and zeaxanthin include kale, spinach, turnip greens, romaine lettuce, broccoli, zucchini, garden peas and Brussel sprouts).

People with moderate AMD, should consult a doctor before taking additional amounts, especially high-dosage supplements.

Royal National Institute of the Blind

Tel: 0845 766 9999
Email: helpline@rnib.org.uk
Website: www.rnib.org.uk

Macular Disease Society

Tel: 0845 241 2041
Email: help@maculardisease.org
Website: www.maculardisease.org

This article was last medically reviewed by Dr Trisha Macnair in April 2009.