Macular degeneration

What is macular degeneration?

Macular degeneration (also known as age-related macular degeneration) occurs when cells in the macula - the central area of the retina - degenerate. The retina is a light sensitive layer that lines the interior of the eye. It is composed of light sensitive cells known as rods and cones. See Anatomy of the Eye for further information.

Damage to the macula affects central vision which is needed for reading, writing, driving, recognising people's faces and doing other fine tasks. The damage occurs at the level of the layer of cells within the retina called the retinal pigment epithelium (RPE).

The rest of the retina is used for peripheral vision - the 'side' vision which is not focused. Therefore, without a macula, it is still possible to get about, be aware of objects and people and be independent. However, the loss of central vision will severely affect normal vision.

Visual loss in age-related macular degeneration (AMD) can occur within months, or over many years, depending on the type and severity. There are two main types of AMD - 'wet' and 'dry'. 'Wet' AMD is the more severe but is more treatable.

Symptoms of macular degeneration

Early symptoms

The main early symptoms are:

• Worsening of central vision despite using usual glasses.

• Needing a brighter light to read by.

• Words in a book or newspaper becoming blurred.

• Colours appearing less bright.

• Difficulty recognising faces and facial expressions.

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, a person may not be aware of it until it's quite advanced, as the other eye will still see things normally. When both eyes are affected, symptoms become much more obvious.

Later symptoms

As the condition worsens, a 'blind spot' then develops in the middle of the 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 with 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 it does not mean you are developing a serious mental illness. If visual hallucinations do occur, they typically improve by 18 months.

Peripheral vision is not affected with AMD and so it does not cause total loss of vision.

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 common is macular degeneration?

Age-related macular degeneration 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 12 in 100 people aged over 80 have AMD severe enough to cause serious visual impairment. Women are more likely than men to develop AMD.

White people 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 overweight and those with cardiovascular disease.

Dry macular degeneration

This is the most common form of macular degeneration 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.

Wet macular degeneration

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.

If a person has wet AMD (see below) in one eye the risk of developing wet AMD in the second eye is about 1 in 4.

Various systems exist to classify AMD. Both wet and dry AMD can be 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. Wet and dry AMD are sometimes classified as early or late, and wet AMD as active or inactive.

Causes of macular degeneration

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.

Risk factors

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, the 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.

• Being white.

Diagnosing macular degeneration

If symptoms suggestive of AMD develop, a doctor or optician (optometrist) will refer to an eye specialist (ophthalmologist). This should be done urgently, in case the diagnosis is wet AMD (which can worsen rapidly but which can be treated).

Diagnosing macular degeneration usually involves the following:

Eye examination

The Amsler grid is a tool that opticians and ophthalmologists use to detect vision problems resulting from damage to the macula (the central part of the retina) or the nerve that transmits what you can see to the brain (optic nerve). When looking at a special piece of paper with horizontal and vertical lines, if there is any section of the lines missing or distorted then AMD is a possible cause of the visual problem.

The ophthalmologist will examine the back of the 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.

Ocular coherence tomography

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.

Fluorescein angiography

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 the arm. Then, by looking into the 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.

Macular degeneration treatment

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.

• Aflibercept.

• Faricimab.

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.

Intraocular lens systems

This 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.

• Damage to the eye itself.

NICE recommends that implanting a miniature lens system implantation can improve both vision and quality of life in the short term. However, there is insufficient evidence for short-term safety or for long-term benefit and safety. Therefore, NICE recommends that the procedure should only be used with special arrangements for clinical governance, consent and audit or research.

Older treatments

Older treatments for wet AMD are less effective than anti-VEGF injections. These 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.

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).

Does diet matter inmacular degeneration?

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.

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, these supplements should not be started before getting advice from a GP or a consultant eye specialist (ophthalmologist).

Practical help for macular degeneration

When 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. An ophthalmologist can complete a 'Certificate of Visual Impairment', and a person may then be entitled to certain benefits.

What else can I do?

• For smokers, try to stop. Smoking is a risk factor for many illnesses, including AMD. The NHS can provide help, support and medicines to assist stopping smoking.

• Eating a healthy balanced diet to ensure plenty of the types of vitamins that may help in AMD.

• Staying safe with regards to driving. A person registered as having sight impairment should not drive and should notify the Driver and Vehicle Licensing Agency (DVLA). If in any doubt, it is essential to speak to an eye specialist or contact the DVLA for advice.

• Regular sight tests. An eye test can often pick up the first signs of an eye condition before any change in vision occurs. An optician (optometrist) can advise how often an eye check-up is needed, depending on general health, age, family history and other medical conditions. Early detection of problems often allows more effective treatment.

Dr Mary Lowth is an author or the original author of this leaflet.