Age-related macular degeneration is the most common cause of sight impairment in those aged over 50. It causes a gradual loss of central vision, which we need for for detailed work and for things like reading and driving. Edge vision (peripheral vision) is not lost.
Visual loss in age-related macular degeneration can occur within months, or over many years, depending on the type and severity. There are two main types of age-related macular degeneration - 'wet' and 'dry'. 'Wet' age-related macular degeneration is most severe but more treatable.
Understanding the back of the eye
The retina is made up of two main layers. There is an inner layer of 'seeing cells' called rods and cones. These cells react to light and send electrical signals via the optic nerve to the brain. The cones help us to see in the daylight, and form colour vision. Rods help us to see in the dark. The outer layer - the retinal pigment epithelium (RPE) - is a layer of cells behind the rods and cones. The RPE helps to nourish and support the rods and cones. It acts like a filter, keeping harmful substances away from from the sensitive cells.
The macula is the small area of the retina where your central vision is formed. It is about 5 mm in diameter. The macula is the area which is the most densely packed with rods and cones. In the middle of the macula is an area called the fovea, which only contains cones. The fovea forms your pinpoint central vision.
The tiny blood vessels of the choroid bring oxygen and nutrients to the retina. Bruch's membrane is a thin protective barrier between the choroid and the delicate retina.
When you look at an object, light from the object passes through the cornea, then the lens, and then hits the retina at the back of the eye.
What is age-related macular degeneration (AMD)?
AMD (also called AMRD) occurs when cells in the macula degenerate. Damage to the macula affects your central vision which is needed for reading, writing, driving, recognising people's faces and doing other fine tasks.
The rest of the retina is used for peripheral vision - the 'side' vision which is not focused. Therefore, without a macula you can still see enough to get about, be aware of objects and people and be independent. However, the loss of central vision will severely affect normal seeing.
Who develops age-related macular degeneration (AMD)?
AMD) only develops in older people (there are other rare types of macular degeneration which occur in younger people). AMD is the most common cause of severe sight problems (visual impairment) in the developed world. It is more common with increasing age.
It is rare under the age of 60. It usually begins in one eye. About 5 in 100 people aged over 65 and about 1 in 8 people aged over 80 have AMD severe enough to cause serious visual impairment. About twice as many women over the age of 75 have AMD compared with men of the same age. People of Caucasian ethnicity are more likely to develop AMD than those of African or Asian ethnicity. It is also more common in those who smoke, those who are oveweight and those with cardiovascular disease.
What are the types of age-related macular degeneration (AMD)?
This is the most common form and occurs in 9 in 10 cases. In this type the cells in the RPE of the macula gradually become thin (they 'atrophy') and degenerate. This layer of cells is crucial for the function of the rods and cones which then also degenerate and die. Dry AMD is a gradual process as the number of cells affected increases: it usually takes several years for vision to become seriously affected. Many people with dry AMD do not totally lose their reading vision. If only one eye is affected you may not be aware of the change in your vision, and it may be detected unexpectedly during an eye test.
Wet AMD may also be called neovascular or exudative AMD. It occurs in about 1 in 10 cases. In wet AMD, in addition to the retinal pigment cells degenerating, fragile new blood vessels grow from the tiny blood vessels in the choroid into the macular part of the retina. These vessels tend to leak blood and fluid. This can damage the rods and cones and cause scarring in the macula, causing further vision loss. Wet AMD can cause distortion of your central vision, and causes severe visual loss over quite a short time - sometimes weeks or months. Very occasionally, if there is a bleed (haemorrhage), this visual loss can occur suddenly, within hours or days.
If you develop wet AMD (see below) in one eye the risk of developing wet AMD in the second eye is about 1 in 4.
Both wet and dry AMD are further classified as early, intermediate or advanced, according to the degree of damage to the macula. 6 of every 10 cases of intermediate/advanced AMD are due to wet AMD.
What causes age-related macular degeneration (AMD)?
In people with AMD the cells of the RPE stop working work so well with advancing age. They gradually fail to take enough nutrients to the rods and cones and do not clear waste materials and byproducts. As a result, tiny abnormal deposits called drusen develop under the retina. In time, the retinal pigment cells and their nearby rods and cones degenerate, stop working and die. This is the dry type of AMD.
In wet AMD, new blood vessels grow into the layers of the retina from the choroid. The reason why this happens in some cases of AMD is not known, although waste products or shortage of oxygen may be involved.
Certain risk factors increase the risk of developing AMD. These include:
- Smoking tobacco.
- High blood pressure.
- A family history of AMD. (AMD is not a straightforward hereditary condition. However, your risk of developing AMD is increased if it occurs in other family members.)
- Sunlight. Laboratory studies suggest that the retina is damaged by sunlight rays (UVA and UVB rays).
- Being very overweight.
- Poor diet.
AMD is more common in people from white (Caucasian) racial backgrounds than from other racial groups.
What are the symptoms of age-related macular degeneration (AMD)?
AMD is painless. Symptoms of dry AMD tend to take 5-10 years to become severe. However, severe visual loss due to wet AMD can develop more quickly.
If AMD develops in one eye only, you may not be aware of it until it's quite advanced, as the other eye will still see the things you are looking at with your central vision. When both eyes are affected you are more likely to notice symptoms.
The main early symptom is worsening of central vision despite using your usual glasses. In the early stages of the condition you may notice that you need brighter light to read by. Words in a book or newspaper may become blurred. Colours may appear less bright and you may have difficulty recognising faces and facial expressions.
As the condition worsens, a 'blind spot' then develops in the middle of your visual field. This is not always initially noticeable. However, it tends to become larger over time as more and more rods and cones degenerate in the macula.
One early symptom of wet AMD is visual distortion. Typically, straight lines appear wavy or crooked. For example, the lines on a piece of graph paper, or the lines between tiles in a bathroom.
Visual hallucinations (also called Charles Bonnet syndrome) can occur if you have severe AMD. People see different images, from simple patterns to more detailed pictures - often they see complicated images of children or animals. The experience can be upsetting but is less frightening if you are aware that it can happen in AMD. Importantly, it does not mean you are developing a serious mental illness. If you do develop visual hallucinations they typically improve by 18 months.
Peripheral vision is not affected with AMD and so it does not cause total loss of vision.
Always see a doctor or optometrist promptly if you develop visual loss or visual distortion.
Older people should in any case have regular eye checks to check each eye separately for early AMD (and to check for other eye conditions such as glaucoma).
How is age-related macular degeneration (AMD) diagnosed?
If you develop symptoms suggestive of AMD, your doctor or optician (optometrist) will refer you to an eye specialist (ophthalmologist). This should be done urgently, in case you have wet AMD (which can worsen rapidly but which can be treated).
The ophthalmologist may ask you to look at a special piece of paper with horizontal and vertical lines to check your visual fields. If you find that any section of the lines is missing or distorted then AMD is a possible cause of the visual problem. The ophthalmologist will examine the back of your eye with a slit-lamp microscope. Digital photographs can be taken of the retinae. The ophthalmologist will look for the typical changes that occur with dry AMD and wet AMD.
Another test called ocular coherence tomography is becoming more commonly used. This is a non-invasive test that uses special light rays to scan the retina. It can give very detailed information about the macula and can show if it is abnormal. This test is useful when there is doubt about whether AMD is the wet or dry form, and to monitor treatment.
If wet AMD is diagnosed or suspected then a further test called fluorescein angiography may be done. For this test a dye is injected into a vein in your arm. Then, by looking into your eyes with a magnifier the ophthalmologist can see where any dye leaks into the macula from the abnormal leaky blood vessels. This can give an indication of the severity of the condition.
What is the treatment for age-related macular degeneration (AMD)?
Whether or not there is a treatment that can prevent progression, or even reverse your condition, it is important to maximise the sight you do have.
Low vision rehabilitation and low vision services are offered by hospital eye departments and information can be found from the Macular Society and the Royal National Institute of Blind People (RNIB).
Stopping smoking and protecting the eyes from the sun's rays by wearing sunglasses are important in slowing progression of the condition.
A healthy balanced diet rich in antioxidants can be beneficial, as may the addition of dietary supplements (see below for details).
Treatment for dry AMD
For the more common dry AMD, there is no specific treatment yet. Remember that in this type of AMD the visual loss tends to be gradual, over 5-10 years or so, and peripheral vision will not be lost. Intraocular lens systems (see below) are a recent development which may eventually offer hope for advanced AMD.
Treatment for wet AMD
For the less common wet AMD, a treatment called anti-vascular endothelial growth factor (anti-VEGF) may halt or delay the progression of visual loss.
VEGF is a chemical that is involved in the formation of new blood vessels in the macula in people with wet AMD. By blocking the action of this chemical, it helps prevent the condition from progressing and may partially reverse it. Anti-VEGF medicines include ranibizumab, pegaptanib and aflibercept. Another medicine called bevacizumab is not licensed for treating AMD but is cheaper and appears equally effective.
The anti-VEGF medicines are injected using a fine needle directly into the globe of the eye. Injections are generally needed every four weeks for up to two years. Very specific criteria have been set out by the National Institute for Health and Care Excellence (NICE) to determine which patients are eligible for treatment.
Anti-VEGF injections will improve vision in about one in three people treated. However, treatment in most people will maintain vision and prevent the condition from becoming worse. About one person in every ten treated, will not respond at all.
Older treatments for wet AMD are less effective than anti-VEGF injections. They included laser treatment (which is difficult close to the macula, as it causes scarring and loss of vision) and photodynamic therapy. In photodynamic therapy, a medicine called verteporfin is injected into a vein and binds to the newly formed abnormal blood vessels in the macula, allowing them to be targeted with a type of laser. It did not work in all cases, although the success rate in preventing progression was good; however, it did not restore vision.
Intraocular lens systems
This relatively new approach may eventually benefit patients with end-stage AMD of either type.
A series of lenses (or a miniature telescope) is used to deflect the central visual image away from the diseased macula and on to a functional part of the retina. The lenses focus and enlarge the central image in this new undamaged area. The brain appears able to adapt to using the healthy part of the retina to view central images. Patients usually require visual rehabilitation.
In studies so far, more than two thirds of patients have significant improvement in their vision. However, the complications can be serious, including raised pressure in the eyes, fogging of the new lenses or the cornea, or even damage to the eye itself. The cost of this treatment is currently high as the lenses have to be tailored to the individual patient; it is unlikely to be available on the NHS in the near future.
Does diet matter in age-related macular degeneration (AMD)?
Certain groups of people with AMD can benefit from vitamin and mineral supplements. These supplements can slow down the progression of AMD. They are thought to be most beneficial in people with intermediate or advanced AMD.
A combination of high-dose vitamins and minerals called AREDS2 has been tested and found to be most effective. These include:
- 500 mg vitamin C
- 400 IU vitamin E
- 10 mg lutein
- 2 mg zeaxanthin
- 25 mg zinc
- 2 mg copper
High doses of vitamins and minerals can lead to side-effects in some people. Vitamin E has been linked with an increased risk of heart failure in people with diabetes or blood vessel (vascular) disease. Zinc may increase the risk of developing bladder and kidney problems. Because of these potential problems, you should talk to your GP or ophthalmologist before starting these supplements.
Practical help for age-related macular degeneration (AMD)
When your vision becomes poor, it is common to be referred (by your ophthalmologist) to a low vision clinic. Staff at the clinic provide practical help and advice on how to cope with poor and/or deteriorating vision.
Help may include magnifying lenses, large print books, and bright lamps which may assist reading. Non-optical gadgets such as talking watches and kitchen aids can help when vision is limited.
Being registered as visually impaired or severely visually impaired may be helpful. Your consultant eye specialist (ophthalmologist) can complete a 'Certificate of Visual Impairment'. You may then be entitled to certain benefits.
What else can I do?
- If you smoke, try to stop. Smoking is a risk factor for many illnesses, including age-related macular degeneration (AMD). The NHS can provide help, support and medicines to assist stopping smoking.
- Eat a healthy balanced diet to try to make sure you get plenty of the types of vitamins that may help in AMD.
- Stay safe with regards to driving. If you are registered as having sight impairment you should not drive and should notify the Driver and Vehicle Licensing Agency (DVLA). If in any doubt speak to your eye specialist or contact the DVLA for advice.
- Consider regular sight tests as you become older. An eye test can often pick up the first signs of an eye condition before you notice any change in your vision. Your optician (optometrist) can advise you how often you need to have an eye check-up, depending on your general health, age, family history and other medical conditions. Early detection of problems often allows more effective treatment.
Dr Tim Kenny
Dr Mary Lowth
Dr Colin Tidy