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. It can degenerate due to age and hence the term“Age-related, macular degeneration” – or AMD.
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.
What causes it?
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.
What are the symptoms?
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 the age of 50 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 have a relative with the condition.
What’s the treatment?
Currently, there’s no medical treatment for dry AMD. However, not smoking and eating a healthy diet may help to slow the rate of deterioration. High doses of beta-carotene, vitamins C and E, and zinc may help to slow down visual loss for some people who already have AMD . 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. They may not be available on the NHS and are currently being reviewed by the National Institute for Clinical Healthand Excellence (NICE). A
new drug treatment for wet AMD, called anecortave acetate, aims to stop newblood vessels forming, but is injected behind the eye rather than into it.
Currently, it’s only at the experimental stage.
Can it be prevented?
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 may help reduce the risk of a person developing AMD, although other studies suggest the scientific evidence isn’t 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 kale and leafy green vegetables. People with moderate AMD, should consult a doctor before taking additional amounts, especially high-dosage supplements.
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