Your guide to
What are the eye tests?
The ophthalmologist will check the pressure inside your eye, this is called a tonometry test. Not everyone with glaucoma has raised eye pressure (called ocular hypertension) but this is one of the main things they’ll look out for.
The ophthalmologist will also check your visual fields: this assesses the range of side (peripheral) vision in each eye, measuring how much you can see at the edge of your vision. Visual damage due to glaucoma often creates a particular pattern of visual field loss which the ophthalmologist can identify.
They will also examine the front of your eye, using a specialist lens which focuses on the area where fluid drains out of the eye. This area of drainage is called the anterior chamber angle and is formed by the natural junction between two structures in the eye: the front of the eye (the cornea), and the coloured part of the eye (the iris).
This area is of particular interest as a narrowing of the anterior chamber angle can be a cause of glaucoma. A simple way to think of the drainage angle is like a bath plug. If the plug gets blocked, or the plug holes narrow, the bath will be slower to drain. This investigation of the anterior chamber angle is called a gonioscopy test. Doctors will also look for debris in the fluid at the front of the eye which can cause a rise in pressure by blocking the drainage angle.
The ophthalmologist will check the appearance of the optic nerve at the back of your eye, too, as this can be affected by glaucoma. They will look to see if the nerve, or the disc, has ‘cupped’.
They may also use an OCT scan to measure the thickness of the nerve fibre layers at the back of your eye. By using information from all these tests the ophthalmologist can tell if you have glaucoma and, importantly, what type. So how many types of glaucoma are there?
What is open-angle glaucoma?
This is the most common type of glaucoma. It develops gradually and painlessly, so an eye test is usually the only way to detect it. Generally, the risk of developing it increases with age, but there are several other risk factors too, including high levels of short-sightedness (if your prescription is more than >-6.00), a family history of glaucoma, diabetes and Afro-Caribbean ethnicity.
‘Open-angle’ means that the angle in your eye where the iris meets the cornea, and where fluid drains out, is wide and open. However, the drainage canals may be working less efficiently, which could be causing a rise in eye pressure which, in turn, can damage the optic nerve. It’s this that can lead to glaucoma development.
This glaucoma is a type of open-angle glaucoma and tends to run in families. It can start in your 20s and 30s, so it’s important to detect and treat it early in order to protect your vision for the rest of your adult life. Essentially, make sure you’re getting regular eye tests.
Usually, it can affect more men than women and tends to be more common in those who are short-sighted. It’s called ‘pigmentary glaucoma’ because the colour pigment from the iris is shed and can cause a blockage to the fluid draining from the front of the eye.
Exfoliation syndrome, also known as pseudoexfoliation, can happen when abnormal proteins (either exfoliation or pseudoexfoliation material) gradually accumulate in the drainage system of the eye. It’s another form of open-angle glaucoma.
You can read about the treatment options for open-angle glaucoma here.
What is angle-closure glaucoma?
Also known as narrow-angle glaucoma, this is much less common than open-angle glaucoma. This type of glaucoma develops when the drainage channel at the front of your eye becomes narrowed or closes up.
Acute angle-closure glaucoma
If angle-closure develops suddenly it is usually very painful and gives distinctive symptoms, including nausea, vomiting, and seeing haloes around lights. If you have these symptoms, you’ll need to go to a hospital straight away where they can bring the pressure down with medicine and/or surgery.
Chronic angle-closure glaucoma
For a very small number of people, angle-closure glaucoma can come on slowly. You may not know you have it unless you have an ‘acute attack’, as above, or if your optician detects during an eye test that this is something you might be prone to.
Learn about the treatment options for angle-closure glaucoma here.
What is normal-tension glaucoma?
Also called low-tension or normal-pressure glaucoma, this causes damage to the optic nerve even though the pressure in the eye is not unusually high. This can happen due to the unfortunate reason that some people may have nerve fibre layers that are simply more prone to damage — even at normal pressure levels. However, research is still inconclusive as to why this happens. A visual field test and examination of the back of the eye is done in a routine eye test, along with an OCT scan (in select stores) that can help with diagnosing this condition.
What is secondary glaucoma?
There are other rarer types of glaucoma which are called ‘secondary’ glaucoma and happen as a result of another condition.
Neovascular glaucoma develops when new blood vessels block fluid draining from the front of the eye. It happens most frequently in association with diabetic retinopathy, a condition where new weak blood vessels also grow at the back of the eye. Other conditions affecting blood vessels in the eye can also cause this type of glaucoma.
If you are diagnosed with uveitis, you may also be at risk of a rise in intraocular pressure (fluid pressure within the eye). Uveitis is an inflammation inside the eye and can cause the pressure to rise inside the eye in three linked ways.
Firstly, the inflammation can create debris which blocks the drainage of fluid inside the eye. Secondly, in the longer term, it can cause scarring which further blocks fluid outflow. Thirdly, you may be advised to use steroid eye drops to reduce inflammation, but this can also cause a rise in eye pressure as a side effect
Medication and surgery can treat uveitic glaucoma and, if you’re worried, you should talk to the team that is managing your uveitis regarding your treatment options.
Discover more about the link between uveitis and glaucoma here.
Glaucoma runs in families: if a member of your close family has had glaucoma you’re at higher risk of having the condition.
In fact, anyone over 40 who has a relative with glaucoma is entitled to an NHS-funded eye test every year in England. It’s important you attend your eye test even if you think your vision is great and you aren’t having problems with your glasses (if you wear them).
Learn more about hereditary glaucoma here.
Congenital means a condition is present at birth. A tiny number of babies are born with raised pressure inside their eyes. This happens when the filter system in the eye does not develop as it should. The fluid that flows in and out of the eye does not drain well and the pressure inside the eye rises as a result. This can cause sight loss if left undetected. Once it has been detected, however, it can be treated with medications such as eye drops, and surgery.
Find out more information about congenital glaucoma here.
Traumatic glaucoma can develop after an injury to the eye. This could be a knock or bruise, known as blunt trauma, or one which penetrates the eye. It can happen at the time of the injury or later.
Trauma can cause damage and bleeding in the eye which can clog up the tiny channels that drain fluid from the front of the eye. This means that the fluid which normally circulates inside the eye builds up — causing a rise in pressure.
This, in turn, can damage the optic nerve. If you have an eye injury or if you’re concerned about any eye trauma, visit your local eye hospital so they can check for bleeding and measure the pressure in your eye. Sometimes the pressure returns to normal when the bleeding stops; other times eye drops or surgery may be needed.
Whichever type of glaucoma you may have or develop, don’t worry. There’s more information to help you learn about the condition on our glaucoma hub.
If you want to learn about glaucoma treatment options, then you can read our overview here.