A group of eye conditions, glaucoma affects vision. It often affects both eyes, usually in varying degrees. One eye may develop glaucoma quicker than the other.
If left untreated, glaucoma can cause blindness. But if it is diagnosed and treated early enough, further damage to vision can be prevented.
Glaucoma occurs when the drainage tubes (trabecular meshwork) within the eye become slightly blocked. Thisprevents eye fluid (aqueous humour) from draining properly.
When the fluid cannot drain properly, pressure builds up. This is called intraocular pressure. This can damagethe optic nerve, which connects the eye to the brain, and the nerve fibres from the retina (the light-sensitive nerve tissue that lines the back of the eye).
Types of glaucoma
There are four main types of glaucoma:
- Chronic open-angle glaucoma:this is the most common type of glaucoma and develops very slowly.
- Primary angle-closure glaucoma:this is rare and can occur slowly (chronic) or may develop rapidly (acute) with a sudden, painful build-up of pressure in the eye.
- Secondary glaucoma:this occurs as a result of an eye injury or another eye condition, such asuveitis (inflammation of the middle layer of the eye).
- Developmental glaucoma (congenital glaucoma): this is rare but can be serious. It is usually present at birth or develops shortly after birth. It is caused by an abnormality of the eye.
See the box (left) for more information about the terms used to describe the different types of glaucoma.
How common is glaucoma?
In England, about 480,000 people have chronic open-angle glaucoma. Among white Europeans, about 1 in 50 people above40 years old and 1 in 10 people above 75 years old has chronic open-angle glaucoma. It may be more common among people of black-African or black-Caribbean origins.
The other types of glaucoma are much less common. Among white people, acute angle-closure glaucoma may affect about 1 in 1,000 people. It is more common among people of Asian origin, affecting around 1 in 100 of them.
Glaucoma can be treated with eye drops, laser treatment or surgery (see Glaucoma – treatment). However, early diagnosis is important because any damage to the eyes cannot be reversed. Treatment aims to control the condition and minimise any future damage.
Attending regular optician appointments will help to ensure that any signs of glaucoma can be detected early and allow treatment to begin. Without treatment, glaucoma can eventually cause blindness.
Symptoms of glaucoma
The symptoms of the different types of glaucoma are explained below.
Chronic open-angle glaucoma
In cases of chronic glaucoma, there are usually no noticeable symptoms because the condition develops very slowly. People with this type of glaucoma often do not realise that their sight is being damaged. This is because the first part of the eye to be affected is the outer field of vision (peripheral vision). Vision is lost from the outer rim of the eye, slowly working inwards towards the centre.
Changes in vision are often linked to getting older, which is why it is so important to have your eyes checked regularly. You should have an eye test at least every two years, or more frequently if your optometrist (healthcare professional who tests sight) recommends it.
Acute angle-closure glaucoma
Due to the rapid development of acute glaucoma, the symptoms are often severe. They include:
- intense pain
- redness of the eye
- tender eye area
- seeing halos or ‘rainbow-like’ rings around lights
- misty vision
- loss of vision in one or both eyes that progresses very quickly
As a result of these symptoms, some people may also feel sick or be sick.
The symptoms of acute glaucoma are not constant. They can last for one or two hours before disappearing again. But each time the symptoms occur, your vision is damaged a little more.
It is important to contact your GP straight away if you have any of the above symptoms, because early treatment can prevent further damage occurring.
If you have symptoms outside your GP’s normal working hours, visit your nearest accident and emergency (A&E) department. The healthcare professionals at A&E will relieve the pressure within your eye and treat any pain.
Secondary glaucoma is caused by other conditions or eye injuries, such asuveitis (inflammation of the middle layer of the eye). It is possible for the symptoms of glaucoma to be confused with the symptoms of the other condition. For example, uveitis often causes painful eyes and headaches.
However, the glaucoma may still cause misty vision and rings or halos around lights.
Recognising the symptoms of developmental glaucoma (also known as congenital glaucoma) can be very difficult due to the young age of the baby or child.
However, your child may display symptoms, such as:
- large eyes due to the pressure in the eyes causing them to expand
- being sensitive to light (photophobia)
- having a cloudy appearance to their eyes
- having watery eyes
- jerky movements of the eyes
- having a squint, which is an eye condition that causes one of the eyes to turn inwards, outwards or upwards, while the other eye looks forward
If you notice any of these symptoms, visit your GP or optometrist as soon as possible.
|Eyes: Cataracts, Glaucoma and Macular Degeneration(Understanding) (Family Doctor Books)||Glaucoma: A Patient’s Guide to the Disease|
Causes of glaucoma
Glaucoma is caused by a blockage in part of the eye. This prevents fluid draining out of the eye, and increases pressure in the eye, called intraocular pressure.
How the eye works
The eyeball is filled with a watery substance called aqueous humour, which creates pressure in the eye to give it shape. In healthy eyes, this fluid constantly flows in and out of the eye. It drains back into the bloodstream at the same rate that it is produced to maintain the correct pressure.
Glaucoma occurs when the drainage tubes (trabecular meshwork) within the eye become slightly blocked, preventing the aqueous humour from draining properly. An obstruction within the eye, such as a blood vessel blocking the trabecular meshwork, can also prevent fluid from draining properly.
When the fluid cannot drain properly, the pressure in the eye builds up and can damage the optic nerve, which is the nerve that connects the eye to the brain, and the nerve fibres from the retina (the light-sensitive nerve tissue that lines the back of the eye).
It is not known why the drainage tubes become blocked or why other parts of the eye obstruct the tubes.
There are various factors that can increase your risk of developing glaucoma. These are explained below.
- Age: glaucoma becomes more likely as you get older. In the UK, chronic open-angle glaucoma affects 1 to 2 people in every 100 who are over 40 years old, and 4 to 5 people in every 100 who are over 80 years old.
- Ethnic origin: people of African or Afro-Caribbean origin are at increased risk of developing chronic open-angle glaucoma. People of Asian origin are at increased risk of developing acute angle-closure glaucoma.
- Short sightedness(myopia): people who are short-sighted are more likely to develop chronic open-angle glaucoma.
- Ocular hypertension (OHT – raised pressure in the eye): people with OHT are at increased risk of developing chronic open-angle glaucoma. Your optometrist will be able to diagnose OHT (see Glaucoma – diagnosis).
- Family history: if you have a close relative, such as a parent, brother or sister who has glaucoma, you are at increased risk of developing the condition yourself. You should therefore have regular eye tests to monitor the condition of your eyes.
- Medical history: people withdiabetes, which is a condition caused by too much glucose in the blood, may be at increased risk of developing glaucoma.
If you have glaucoma, it can take a long time before you realise that you have a problem with your eyesight. This is because glaucoma usually damages the outer edge of the eye and works slowly inwards. You may not notice a problem until the glaucoma is near the centre of your eye.
It is therefore very important to have regular eye tests so that any problems can be detected and treated as early as possible.
You should have an eye test at least every two years or more frequently if advisedby your optometrist (a healthcare professional who tests sight). For example, they may suggest that you have more frequent eye tests if you have a close blood relative with glaucoma, such as a parent,brother or sister.
Tests for glaucoma
There are several glaucoma tests that your optometrist can perform. They are painless and quite quick. The tests should be carried out during the same appointment to ensure that the results are as accurate as possible.
The tests that you may have for glaucoma are explained below.
Eye pressure test (tonometry)
An eye pressure test (tonometry) uses an instrument called a tonometer to measure the pressure inside your eye. A small amount of anaesthetic (painkilling medication) and dye is placed onto your cornea (the transparent layer of tissue that covers the front of the eye). A blue light from the head of the tonometer is held against your eye to measure the intraocular pressure.
Tonometry can diagnose ocular hypertension (OHT – raised pressure in the eye), which is a risk factor for chronic open-angle glaucoma.
Central corneal thickness
The thickness of your cornea will be measured because this is thought to affect how the intraocular pressure is interpreted.
Gonioscopy is an examination of the front outer edge of your eye, between the cornea and the iris (the coloured part of your eye). This is the area where the fluid should drain out of your eye. A gonioscopy can help to determine whether this angle is open or closed (blocked).
Visual field test (perimetry)
A visual field test (perimetry) checks for missing areas of vision.You will beshown asequence of light spots and asked which ones you can see. Some dots will appear in your peripheral vision (around the sides of your eyeball), which is where glaucoma begins.
If you cannot see the spots in your peripheral vision, it may indicate that the glaucoma has damaged your vision.
Optic nerve assessment
Your optic nerve connects your eye to your brain. Your optometrist will use eye drops to enlarge your pupils. They will then examine your eyes using a slit lamp (a microscope with a very bright light) and assess whether your optic nerve has been damaged by the glaucoma.
The eye drops that are used to widen your pupils could affect your ability to drive. Therefore you may need to make alternative arrangements for getting home after your appointment, such as asking a family member to collect you.
If your optometrists suspects that you have glaucoma, they will refer you to an ophthalmologist (see box, right) for further tests. Your ophthalmologist will confirm your diagnosis and find out:
- how developed the glaucoma is
- how much damage the glaucoma has done toyour eyes
- what may have caused the glaucoma
They will then be able to advise you about the treatment that you need (see Glaucoma – treatment).
In some cases, your ophthalmologist will continue to treat you. Butif you have chronic open-angle glaucoma, you may be referred back to your optometrist who will continue your treatment.
Any damage to your vision that is caused by glaucoma cannot be repaired. This is why it is so important to get an early diagnosis so that the glaucoma can be treated and prevented from developing further.
The aim of treatment for every type of glaucoma is to reduce the pressure in the affected eye, called the intraocular pressure.
Eye drops for chronic open-angle glaucoma
Chronic open-angle glaucoma is often treated using eye drops. There are several different types of eye drops that may be prescribed. The choice of eye drops may depend on:
- how your condition is progressing
- whether you have any other medical conditions
- whether you are currently taking any other medications
- whether the eye drops cause any side effects when you use them
The different types of eye drops are described below.
See the box (right) for more information about using eye drops.
Prostaglandin analogues increase the flow of fluid (aqueous humour) out of your eye, which reduces the pressure within your eye (the intraocular pressure). These eye drops are usually used once a day. Side effects include:
- enlarged blood vessels in the white part of your eye, making your eye look red
- changes to your eye colour –it often gets darker
- eyelashes growing thicker and darker
- eye painand irritation
- blepharitis –a condition where the rims of your eyelids become red and swollen
- dry eyes
- sensitivity to light
It is thought that beta-blockers reduce intraocular pressure by slowing down the production of aqueous humour in your eye. They are used once or twice a day and can cause side effects such as:
- a stinging or burning sensation in your eye
- dry eyes
- itchy eyes
Beta-blockers can make some medical conditions worse, so do not use them if you have:
- some heart conditions, such asheart block
See the Health A-Z topic aboutBeta-blockers for more information about this medicine, including their side effects and what medicines they interact with.
Carbonic anhydrase inhibitors
Carbonic anhydrase inhibitors reduce the amount of aqueous humour produced in your eye, which reduces intraocular pressure. These drops are used two or three times a day and may cause:
- a bitter taste in your mouth
- nausea (feeling sick)
- a dry mouth
- eye irritation
Sympathomimetics are thought to reduce the rate of production of aqueous humour and increase the flow of aqueous humour out of the eyes. These eye drops are used twice a day and may cause your eyes to become painful and red.
Some types of sympathomimetics can only be used with caution in people who have:
- high blood pressure
- heart disease
Other treatments for chronic open-angle glaucoma
If the use of eye drops does not improve your symptoms, a different type of treatment may be recommended, such as laser treatment or surgery. These are described in more detail below.
Laser treatment, which useshigh energy beams of light, can be used to open up the blocked trabecular meshwork (drainage tubes) within your eye. This is called laser trabeculoplasty.
Anaesthetic (painkilling) eye drops will be put into your eye and a special lens will be placed in front of your eye. The laser will be shone through the lens and will make small holes in the trabecular meshwork. This allows more fluid to drain out of your eye and reduces the intraocular pressure.
An alternative to laser trabeculoplasty is cyclodiode laser treatment. This involves destroying some of the tissue in the eye that produces aqueous humour. It creates less fluid in the eye, which reduces the intraocular pressure.
Laser treatments are usually quick and painless, although during the procedure you may feel a brief twinge of pain or heat. You may still need to use eye drops (see above) after having laser treatment.
A trabeculectomy is the most common type of glaucoma surgery. It involves removing part of the trabecular meshwork to allow fluid to flow through the eye’s drainage system. The procedure will be carried out under local anaesthetic (you will still be conscious) orgeneral anaesthetic (you will be unconscious).
Other types of surgery include:
- a viscocanalostomy –this operation removes part of the sclera (the white outer covering of the eyeball), enabling the fluid to filter out of your eye and into your body
- a deep sclerectomy operation –this operation involves implanting a tiny device inside your eye to widen the trabecular meshwork
- an aqueous shunt implant –this operation involves placing a tube device into your eye to increase the drainage of fluid out of your eye
Speak to your surgeon to find out more about your procedure and the risks involved.
If you are having surgery, your surgeon may choose to use anti-scarring medicines. These can improve the success of the operation by preventing scar tissue forming as your eye heals. You may be prescribed:
- mitomycin C or
These medications are unlicensed for the treatment of glaucoma. This means that the manufacturers of these medications have not applied for a licence for their medication to be used to treat glaucoma. In other words, the medications have not undergone clinical trials (research that tests one treatment against another) to see if they are effective and safe in treating glaucoma.
Many experts will use an unlicensed medication if they think the medication is likely to be effective and the benefits of treatment outweigh any associated risk. The National Institute for Health and Clinical Excellence (NICE) has issuedguidance for the treatment of chronic open-angle glaucoma. It suggests that these medicines can be used.
If your ophthalmologist (medical doctor who specialises in eye disease) is considering prescribing an unlicensed medication, they should inform you that it is unlicensed, and discuss the possible risks and benefits with you.
Acute angle-closure glaucoma
As acute glaucoma develops rapidly, the condition needs to be treated quickly. The most common forms of treatment for this type of glaucoma include:
- eye drops –see above for further details
- systemic medicines –these are injected into your bloodstream to quickly reduce the pressure in your eye
- laser treatment (called laser iridotomy) – this uses high-energy beams of light to create holes in your iris (coloured part of the eye) to open the angle and enable fluid to flow;both eyes may need to be treated, even if only one has acute angle-closure glaucoma, because this form of glaucoma may develop in both eyes at some point
- surgery –a trabeculectomy (surgery to remove part of the drainage tubes) is the most common form of surgery for acute glaucoma
If you also have a cataract, which is a cloudy patch in the front of your eye, removing it may open the angle in your eye and control the intraocular pressure. See the Health A-Z topic aboutCataract surgery for more information about this procedure.
Acute angle-closure glaucoma may also be treated with a medication called a miotic, such as pilocarpine. Miotics work by opening up the blocked trabecular meshwork, which should improve the drainage of aqueous humour out of your eye. You may need to use these eye drops up to four times a day.
Miotics should be used with caution in people who have certain medical conditions, including:
- heart disease
- high blood pressure
Miotics can also cause some side effects, such as:
- a headache, which may be severe during the firsttwo to fourweeks of treatment
- burning or itchy eyes
- blurred vision, which may affect your ability to drive
Treating other types of glaucoma
For other types of glaucoma, your specialist will usually recommend eye drops, laser treatment or surgery. Your treatment will depend on the type of glaucoma that you have and how advanced it is.
Glaucoma – Complications
Loss of vision is the main complication of glaucoma. This is why early diagnosis and treatment is so important.
Loss of vision
In the UK, glaucoma is responsible for 1 in 10 cases of blindness. If you have some loss of vision due to glaucoma, more information is available on the Royal National Institute of Blind People (RNIB) website. The RNIB offers advice about:
- living with sight loss
- registering your sight loss – this may allow you to access certain benefits
Complications from treatment
If you have surgery to treat glaucoma, there is always a risk of infection. Most infections can be treated with a course of antibiotics (medication to treat bacterial infections).
You may also have a reaction to certain types of eye drops. Speak to the healthcare professionals treating you if you feel unwell while you are being treated for glaucoma.
If you have glaucoma, it could affect your ability to drive. It is your legal obligation to inform the Driver and Vehicle Licensing Agency (DVLA) about a medical condition that could affect your driving ability. Go to the Directgov website to find out how to tell the DVLA about a medical condition.
Regular eye tests are very important in helping to prevent glaucoma.
You are entitled to a free NHS eye test if you are over 40 years old and have a first-degree relative (mother, father, sister or brother) with glaucoma.
You may also be entitled to a free NHS eye test if:
- an ophthalmologist (eye specialist) thinks that you are at risk of developing glaucoma
- you are over 60 years old
Your optometrist (a healthcare professional who tests sight and examines eyes) will usually talk you through each part of the eye test so that you know what they are testing for. When having a sight test, you should inform the optometrist if glaucoma runs in your family.
Royal National Institute of Blind People (RNIB) is the UK’s leading charity offering information, support and advice to almost two million people with sight loss – https://www.rnib.org.uk/
Action for Blind People improve the lives of blind and partially sighted people across the UK. – https://www.actionforblindpeople.org.uk/