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Macular degeneration

Age-related macular degeneration (AMD) is an eye condition that affects a tiny part of the retina at the back of your eye, which is called the macula. AMD causes problems with your central vision, but does not lead to total loss of sight and is not painful.

About age-related macular degeneration

Age-related macular degeneration affects the vision you use when you're looking directly at something, for example when you're reading, looking at photos or watching television. AMD may make this central vision distorted or blurry and, over a period of time, it may cause a blank patch in the centre of your vision.

Causes

At the moment, the exact cause for AMD is not known. Some things are thought to increase your chances of developing AMD:

  • Your age: Age-related macular degeneration develops as people grow older and is most often seen in people over the age of 65, although it can develop in people who are in their 40s and 50s.
  • Your gender: more women have AMD than men, probably because women tend to live longer than men.
  • Your genes: some genes have been identified which seem to be linked to the development of age-related macular degeneration in some people. This has been discovered by looking at families with more than one member who has AMD, but not all AMD is thought to be inherited.
  • Smoking: smoking greatly increases your risk of developing AMD. Studies also show that stopping smoking can reduce your risk of developing AMD.
  • Sunlight: some studies suggest that exposure to high levels of sunlight (particularly the UV light contained in sunlight) throughout your life may increase your risk of developing AMD. Wearing sunglasses to protect your eyes from the UV light in sunlight is a good idea for everyone throughout their life.
  • What you eat: a number of studies have looked at diet as a risk factor for someone developing AMD. At the moment there isn't agreement on how much of a risk factor diet is. There is some evidence that vitamins A, C and E and zinc may help to slow the progression of AMD in people who already have the condition.

Although you cannot change your age or genes, current thinking is that protecting your eyes from the sun, eating a balanced diet with plenty of fresh fruit and vegetables, and stopping smoking may all help to keep your eyes as healthy as possible.

Unfortunately, because the exact cause of AMD is not known you may develop this condition even if you don't have any of these risk factors.

Symptoms

Symptoms vary from person to person, but usually the first problems people notice are with their ability to see detail. You may have problems reading small print, even if you wear your usual reading glasses, or you may find that there is a slight smudge in your sight or that your vision has a small blurred area in the centre. Straight lines may look distorted or wavy or as if there's a little bump in them.

You may also find you become sensitive to bright light or that you see shapes and lights that aren't actually there. Sometimes people may only notice these changes in one eye.

You should have your eyes tested by an optometrist (optician) if:

  • you notice any difficulty with reading small print with your reading glasses
  • straight lines start to look wavy or distorted
  • your vision isn't as clear as it used to be.

The optometrist will be able to measure any changes in your vision and examine the back of your eye. If they detect any changes to your macula or any cause for concern they will arrange an appointment with the ophthalmologist (hospital eye consultant) for further tests.

The macula

AMD affects the macula area of the retina. The macula is a tiny area of your retina which is very important for seeing detail, colour and things directly in front of you.

When the light enters your eye it is focused onto your retina at the back of your eye. The retina includes a number of layers but the most important for vision is a layer made up of cells called photoreceptors. Photoreceptors are cells which are sensitive to light.

The macula, which is about the size of a pinhead, is a specialised area of the retina that contains a few million specialised photoreceptor cells called cone cells. These cone cells function best in bright light levels and allow you to see fine detail for activities such as reading and writing and to recognise colours.

Away from the central macula is the peripheral retina, composed mostly of the other type of photoreceptor called rod cells. They enable us to see when light is dim and provide peripheral (side) vision outside of the main line of sight. Peripheral vision is the sight you have out of the corner of your eye when looking straight ahead.

When someone develops AMD, the cone cells in the macula area become damaged and stop working as well as they should.

Types of AMD

There are two main types of AMD - "wet" AMD and "dry" AMD. They are called "wet" and "dry" because of what happens inside your eye and what the ophthalmologist (hospital eye doctor) sees when examining the inside of your eye, not because of how the eye feels or whether you have a watery or dry eye.

Dry AMD

Dry AMD is the more common type of AMD. It usually develops very slowly and causes a gradual change in your central vision. Dry AMD usually takes a long time, maybe a number of years to get to its final stage. At its worst, dry AMD causes a blank patch in the centre of your vision in both of your eyes. But it doesn't affect your peripheral vision, so never leads to total blindness.

Wet AMD

About 10-15 per cent of people who develop AMD have wet AMD. You develop wet AMD when the cells of the macula stop working correctly and the body starts growing new blood vessels to fix the problem. Unfortunately, these blood vessels grow in the wrong place and cause swelling and bleeding underneath the macula. This new blood vessel growth, medically known as neo-vascularisation, causes more damage to your macula and eventually leads to scarring. Both the new blood vessels and the scarring damages your central vision and may lead to a blank patch in the centre of your sight.

Wet AMD can develop very quickly, making serious changes to your central vision in a short period of time. Treatment is now available for wet AMD, which stops the new blood vessels from growing and damaging your macula. This treatment usually needs to be given quickly before the new blood vessels do too much damage to your macula. If the blood vessels are left to grow, the scarring and the sight loss it causes is usually permanent. Wet AMD doesn't affect your peripheral vision, so it doesn't lead to total blindness.

Both types of AMD

Wet and dry AMD have things in common. They usually affect both your eyes, though sometimes one eye may be affected long before the other. Both wet and dry AMD only affect your central vision and won't affect your vision around the edge of your sight. So neither type of AMD will cause you to lose all your sight.

Some people diagnosed with dry AMD find that, with time, new blood vessels grow and they develop wet AMD. If you have dry AMD and your sight suddenly changes you should always have this checked by your ophthalmologist (hospital eye doctor).

Some people may have wet AMD in one eye and have dry AMD in the other which doesn't develop into wet AMD. Most people, however, have the same type of AMD in both eyes.

Confusingly, people who have had wet AMD for a long time, causing bad scarring on their retina, may be told that their wet AMD has "dried up". This usually means that there are no new blood vessels growing and that your macula has been badly scarred. At this stage of wet AMD, the treatments available wouldn't help.

AMD is not painful and it never leads to a complete loss of vision. Most people with AMD keep their peripheral vision (everything around the edge). This peripheral vision will mean that you should still be able to get around on your own and make use of this vision every day.

Changes in your vision

If you notice a sudden change in your vision, you should always have your eyes examined by an eye health professional. Usually this is an optometrist in the high street. However, if your sight changes very quickly then you can attend the accident and emergency department at your nearest hospital, where an ophthalmologist will be able to check your eyes.

If you have slight changes in your vision then you should arrange for an eye examination with an optometrist (optician). They are trained to detect any eye problems and, if necessary, can refer you to your GP for a further appointment with the ophthalmologist at the hospital.

If you have dry AMD and you notice a sudden change in either of your eyes you should let the hospital know. This is because dry type AMD can develop into wet AMD and if this happens sight saving treatment may be possible.

If you have AMD in one eye and you notice a sudden change in either eye you should let the hospital know as soon as possible. This is because you can have different types of AMD in each eye and treatment might now be of help to you.

Eye examination

To diagnose AMD you need to have your eyes examined by an ophthalmologist. This is done at the hospital once your optometrist or GP has referred you.

At the hospital, your vision will be checked and your pupils dilated to allow the ophthalmologist to look at your macula. Your pupils are dilated with drops that take about 30 minutes to work. They will make you sensitive to light and cause your vision to be blurry. The drops allow the ophthalmologist to see the inside of your eye more easily. The effect of the drops usually wears off in about six hours though sometimes it can happen overnight. It is not safe to drive until the effects have worn off.

The ophthalmologist will look at the inside of your eye using a special microscope called a slit lamp. You place your chin on a rest and the ophthalmologist will sit opposite you. The ophthalmologist will ask you to look in particular directions while shining a light into your eye. This allows them to see your retina and any changes that AMD may have caused. Although very bright, the light cannot damage your eye.

Sometimes the ophthalmologist can tell you whether they think you have AMD or not from this examination. However, you may need a test called a Fluorescein angiogram to find out for certain if you have AMD or to find out whether you have wet or dry AMD.