Age-related 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. AMD 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 (Figure 1).
Figure 1. Central patch of lost vision with macular degeneration
At the moment, the exact cause for AMD is not known. Some things are thought to increase your chances of developing AMD:
- your age: AMD 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 forties and fifties
- 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 AMD 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.
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 your optometrist (optician) if:
- you notice any difficulty with reading small print with your reading glasses, or
- straight lines start to look wavy or distorted or
- your vision isn't as clear as it used to be.
These symptoms are not always a sign of AMD but they should always be checked by an optometrist.
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.
When light enters the eye it is focused onto an area of the retina called the macula. This specialised area of the retina about the size of a pinhead contains a few million specialised photoreceptors 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. with AMD, the cone cells in the macula area become damaged causing reduced central vision.
Types of AMD
There are two main types of AMD – "wet" and "dry", named because of changes in the retina, not because of how the eye feels, or whether you have a watery or dry eye (Figure 2).
Figure 2. Normal retina on the left, wed AMD in the centre and dry AMD on the right.
Dry AMD is the most common type of AMD. It usually develops very slowly and causing a gradual reduction in central vision. Dry AMD usually takes years to get to its final stage. At its worse, 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.
About 10-15 per cent of people with AMD develop "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 with loss of central vision.
Wet AMD can develop over a few weeks, making permanent changes to your central vision. Treatment is 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. Early referral and treatment will give better results. Wet AMD doesn't affect your peripheral vision, so 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 everyday.
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. Small changes should also be checked by an optometrist (optician). They are trained to detect any eye problems and, if necessary, can refer you to Edgbaston Eye Consultants for a detailed retinal examination.
If you have dry AMD and you notice a sudden change in either of your eyes you should book an appointment at Edgbaston Eye Consultants immediately. 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 have it checked out 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.
At Edgbaston Eye Consultants, a consultant ophthalmologist will examine your eyes to confirm the diagnosis of AMD. When you get to the clinic, your vision will be checked, and your pupils dilated to allow the ophthalmologist to look at the macula. Your pupils are dilated with drops that take about 30 minutes to work and allow a better retinal examination. The drops blur your vision for up to 6 hours, though sometimes it can take overnight. It is not advisable to drive until the effects have worn off.
The ophthalmologist looks at the inside of your eye using a special microscope called a slit lamp. You place your chin on a rest and the ophthalmologist examines your retina with a bright light shone into your eye. You will need a scan of the retina called optical coherence tomography (OCT), and sometimes, an injected fluorescein angiogram to see how the blood vessels in your eye are working. The examination and tests will confirm if you have AMD and what type it is.
There is no proven treatment for dry AMD. However, there is good evidence that certain vitamins and micronutrients can slow down its progress, particularly if it has already caused vision changes in one eye. Edgbaston Eye Consultants will help guide you in your diet and with supplements to help protect your eyes.
The treatment for wet AMD is by using a course of injections of anti-vascular endothelial growth factor (anti-VEGF) agents. These counter the chemical which encourages new blood vessel growth in the disease and keep it from progressing, thus minimising further damage to your sight.
The medication is injected into the vitreous cavity of your eye (figure 1), an intravitreal injection. Edgbaston Eye Consultants use a sterile theatre environment to minimise the risk of infection from the injection, this devastating complication is more likely in the ‘clean-room’ injection environments of most hospitals.
Before the injection, you’ll be given anaesthetic eye drops to make your eye numb, and an antiseptic drop to help prevent you from getting an infection.
The injection is not painful, though your eye may ache for a while after the anaesthetic wears off. There is a slight chance that the pressure inside your eye may rise temporarily, but it shouldn’t cause pain or reduce your vision.
The sight in your treated eye may be blurry because of the treatment, but this should wear off within a day. You may also notice a small black circle in the lower part of your vision, from an injected air bubble. This disappears within a few hours. You may also have slight swirls in your vision for a few days following the injection, but this doesn’t always happen to everyone. Your eye may water a bit more after the injection and it may be slightly red or irritated. This normally gets better after a few days. If your eye becomes very painful or very red and hot to touch, or if you notice any worsening of your vision, then you should let your hospital know as soon as possible.
The main complications of this treatment are the chance of a rise in pressure in your eye, retinal detachment (where the retina at the back of the eye peels away from its normal position) and eye infections. These complications are rare, happening to less than one per cent of people having the injections. There are treatments available if any of these complications happen to you. If you’re worried about your eye after the injection, then let your hospital know.
Normally, a course of three injections, one a month for three months, is given to start with. Once you’ve had these three injections, your eyes will be checked at the hospital every four to eight weeks. You may be given further injections if your ophthalmologist thinks they are needed. It’s quite common for people to have more injections after the first three.
Anti-VEGF treatments usually have a high success rate and, in most cases, they stop your sight from getting worse in the short term. In the long term, your vision may gradually worsen even with treatment, but much more slowly than those who have not been treated.
It is important to remember that the main aim of anti-VEGF treatments is to control the swelling and bleeding under the macula by stopping the growth of new blood vessels. It cannot repair any underlying damage that may already be there, which is why you should start your treatment for wet AMD as soon as possible.
The main complications of this treatment are the small chance of a pressure rise in the eye, retinal detachment and eye infections.These happen to less than 1 per cent of those people under treatment and require further intervention.
Usually you will need a course of injections to treat the AMD possibly for years. Edgbaston Eye Consultants has access to the best new treatments that can cut the number of injections needed and free up your life from the AMD treatment cycle. Usually anti-VEGF treatments have a high success rate stabilising vision in the majority of cases with around 40% seeing an improvement in vision.
Further help and support
Most people with AMD will retain sight, though central vision is often poor. There are several ways to make the most of your remaining vision. This may mean making things bigger, using brighter lighting, or using colour to make things easier to see. Edgbaston Eye Consultants will help you cope with your condition. We will regularly measure your vision and chart the state of your disease using special scans. We will be able to tell you if you are legal to drive and certify our testing. If the vision starts to deteriorate, we will signpost you to the best services to maximise low vision. If appropriate, we will register you as sight impaired (partially sighted) or severely sight impaired (blind). Registration acts as a passport to expert help and sometimes to financial concessions. Even if you aren’t registered, a lot of this support is still available to you.
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