Learn more about Glaucoma, including The Symptoms, The Causes, and The Treatments.

The information below is not intended for self diagnose of an eye condition. If you are worried or suffering from an eye problem, please call us on 0208 524 2887 and book in to see us.

Bhavita Magudia
Glaucoma - Explained
February 22, 2019
Back to Common Eye Conditions

What Is Glaucoma

Glaucoma is when the optic nerve, which connects the eye to the brain, becomes damaged. The damage to the optic nerve by Glaucoma can cause the loss of peripheral vision over time. The cause of the damage to the optic nerve is usually raised eye pressure (also known as raised intraocular pressure). ‘Normal’ eye pressure is usually stated as between 8-21mmHg, however ‘normal eye pressure’ can vary from person to person.

Glaucoma is what eyedeal vision like to describe as a silent disease it doesn’t always wave a red flag; it can creep in slowly and therefore requires a comprehensive eye examination to detect it. Early detection is the key to protecting your vision from damage caused by glaucoma.

Different types of glaucoma:

Primary open angle glaucoma

Primary open angle glaucoma or chronic glaucoma is the most common type of glaucoma. Its effects occur slowly over time and do not cause you any pain. The drainage of the aqueous fluid from your eye does not happen as well as it should and this causes the pressure to rise.

Acute Angle Closure Glaucoma

Acute glaucoma is much less common. Acute angle closure glaucoma happens when there is a sudden and more complete blockage of the drainage angle, resulting in sudden build up of eye pressure. This is because the edge of the iris and the front clear layer of the eyes (cornea) come into contact; which stops the fluid from draining away through the drainage angle (trabecular meshwork).

Ocular hypertension

Ocular hypertension means patients naturally have high eye pressures of above 21mmHg. This is not the same as having glaucoma. A diagnosis of ocular hypertension means your pressure is high but there is no damage to the nerve.

However some patients with ocular hypertension can go to develop Glaucoma; patients at risk of developing Glaucoma are treated instead of just being monitored.

Normal tension Glaucoma

Normal tension glaucoma means that your optic nerve is damaged with eye pressure within normal ranges of 8-21mmHg. Your eye pressure will need to be reduced to keep your sight safe and is treated in the same way caused by high eye pressure.

Secondary Glaucoma

An increase in your eye pressure caused by another eye condition(s) you have, for example uveitis. This can lead to damage to the vision and treatment in each case is always aimed at reducing the pressure as well as treating the cause.

Traumatic Glaucoma

Raised eye pressure caused by injury or trauma. Where the injury has damaged the drainage angle or caused internal eye tissues or cells to clog the drainage angle.

Developmental/congenital Glaucoma

A rare type of glaucoma that affects young babies or children, usually caused by an eye or health condition.

Glaucoma - Symptoms

Symptoms can vary depending on the type of glaucoma you have

Open, normal tension, secondary glaucoma

• Your eyesight may feel normal to you

• Your peripheral vision gradually gets worse.

• Tunnel vision where glaucoma has resulted in loss of your peripheral vision, central vision unaffected

• No pain

Closed angle glaucoma

• White or coloured halos around lights

• Red eye

• Blurred vision

• Headache

• Tender around the eye(s)

• Nausea or vomiting

• With mild attacks (often in the evening), your vision may seem “misty” with halos and you may have some discomfort in the eye.

This can happen in one or both eyes but it is rare for both eyes to have an attack at the same time. Acute glaucoma is an emergency and needs to be treated quickly if sight is to be saved.

Congenital/developmental glaucoma

• Unusually large eyes

• Excessive watering of the eyes

• Cloudy or hazy eyes

• Light sensitivity

Glaucoma - Causes

Everyone has eye pressure; we need that eye pressure to keep the eyeball in shape. The front of the eye doesn’t have a vast blood supply like the retina, and so a fluid called aqueous humour is produced. This aqueous humour provides the front of the eyes with the nutrients required to stay healthy. The ciliary body sits behind your iris and produces the fluid aqueous humour, which passes through the pupil into the front of the eye. Once the eyes have used the aqueous humour, it needs to drain away through the drainage angle called the trabecular meshwork, which is between the iris and the cornea (clear layer at the front of the eyes).

This balance of aqueous humour production and drainage gives us our eye pressure.  When either too much fluid is being produced or not enough is being drained away, this results in a rise high eye pressure. Raised eye pressure begins to damage the optic nerves, as it cannot sustain the raised or high eye pressure. Optic nerve damage can also occur because the nerve is naturally weak due to poor blood supply and sensitive to fluctuations in normal eye pressure. When the delicate optic nerves become damaged over time because of raised eye pressure, it is called Glaucoma.

People at Risk of Glaucoma

• People Over 60

• Family history of Glaucoma you are at a much higher risk (can be up to 4 times) than the rest of the population.

• African ethnicity can be up to six to eight times more at risk.

• Asian ethnicity appear to be at increased risk for angle-closure glaucoma

• Japanese ethnicity are at higher risk for normal tension glaucoma

• Steroid Users: Some evidence links steroid use to glaucoma.

• Eye Injury or trauma to the eyes

• If you have diabetes you have an increased risk

• Short sightedness

• Hypertension

• Central corneal thickness less than .5 mm

• Congenital eye or health condition

Glaucoma - Treatments

Tests That Detect Glaucoma

Most people should have their eyes tested yearly. It is even more important to have a regular annual eye examination if you are in one or more of the groups at greater risk.

NHS eye tests are provided for anyone with Glaucoma or over 40 years old with a family history. A free basic NHS eye test does not cover all the tests required to detect Glaucoma. Having all the tests is much more effective in detecting glaucoma early rather than just having one or two of the tests.

The Six tests used to detect glaucoma

• Tonometry: known as the eye pressure check

• Visual fields test: to check the health of the nerve and retina

• Gonioscopy: to check the drainage angle of the eye and internal structures

• OCT Scan: a scan of the nerve and check for any nerve damage

• Pachymetry: to check the thickness of the cornea

• Indirect Ophthalmoscopy and/or Direct Ophthalmoscopy: to check the health of the nerve

All these tests are covered in our GOLD eye test available to NHS (at a reduced charge) and Private patients.

The Glaucoma tests explained


Tonometry measures the pressure within your eye. During tonometry, eye drops are used to numb the eye. Then the Optician uses a device called a tonometer to measure the inner pressure of the eye. The Gold standard method of testing someone’s eye pressure is by using the Goldmann or the Perkins machine. The range for normal pressure is 8-21 mmHg, eye pressure is unique to each person.

Visual fields test

The visual field test produces a map of your complete field of vision. This test will help us determine whether your vision has been affected by glaucoma. The gold standard machine is the Humphreys Visual field Analyser. During this test, you will be asked to look straight ahead and then indicate when you can see flashes of light of varying brightness. This allows us to see which parts of the nerve and retina are functioning normally or have been damaged by Glaucoma.


This diagnostic exam helps determine whether the fluid drainage angle where the iris meets the cornea is open and wide or narrow and closed. During the exam, eye drops are used to numb the eye. A hand-held lens is gently placed on the eye. This allows us to see if the drainage angle is blocked (angle-closure or acute glaucoma) or open (open-angle or chronic).

OCT Scan

We use this machine to scan the nerve in 3D producing cross sectional imaging of the nerve. An optical ultrasound of the nerve inside of the eye is taken so we can see the nerve in microscopic detail. Glaucoma causes the nerve to die or become damaged over time. The scan allows us to detect minute changes and diagnose Glaucoma. OCT provides a cross section view of the optic nerve, using light rays instead of X-rays.

We know now that up to 40% of the optic nerve can be damaged before visual field (peripheral vision) tests become abnormal. Recent studies indicating that treatment at the earliest stage of glaucoma results in better long term vision preservation have led to a search for ways to diagnose the problem before the peripheral vision changes occur. Potentially the most accurate way to do this is with OCT.


Pachymetry is a simple, painless test to measure the thickness of your cornea; the pachymeter is gently placed on the front of the eye to measure its thickness. Corneal thickness has the potential to influence eye pressure readings or how we interpret your readings. The procedure takes only about a minute to measure both eyes.

Ophthalmoscopy (indirect or direct)

This procedure helps us examine your optic nerve for glaucoma damage. Eye drops are used to dilate the pupil so that we can get a bigger view of the back of the eye and examine the shape and colour of the optic nerve. The nerve can be viewed in 2D and 3D with this method.

Glaucoma damage to the nerve is irreversible, once the nerve fibres die or become damaged, the nerve fibres in the retina along the same path (the part you see with) also die or become permanently damaged. This causes defects in your field of vision.

Why is it important to have these tests to check for Glaucoma?

Diagnosing glaucoma is not always easy, and careful evaluation of the optic nerve continues to be essential to diagnosis and treatment. The most important concern is protecting your sight. Once glaucoma has been detected, you will be referred onto an Ophthalmologist who specialises in treating Glaucoma. Regular intensive eye tests can help us detect Glaucoma and have you referred to the specialist quicker.

Why Are There So Many Diagnostic tests?

Glaucoma is a process by which the optic nerve cells can become damaged and die, at least partially due to the pressure within the eye. Although there are millions of these cells, one can lose up to 40% of them before being aware of any visual loss.

When diagnosing Glaucoma ideally all of the tests above need to be done to give us the best overall picture. Using just one test and its reading is not always sufficient in detecting Glaucoma. Once all the tests have been completed, all the information is gathered and evaluated to make a diagnosis. Premature diagnosis from one test reading can lead to unnecessary referral. Reading one chapter of a book will not give you the whole story the same goes for diagnosing Glaucoma.

Does eye pressure or visual fields alone tell me I have glaucoma?

The visual field test is only one part of an evaluation. If only the visual field were used to diagnose the condition, we would miss most early stage glaucoma; up to 40% damage can take place before it shows up on your visual fields results. The visual field test is used to help diagnose, tell us the type of glaucoma you have and to help the ophthalmologist create a treatment for you. The visual field provides us a baseline reading for future comparison and information about whether the glaucoma is stable or progressing.

Eye pressure is different for every individual, and should not be used solely to diagnose glaucoma. Many factors affect eye pressure, for instance if you have a tight scarf or drank lots of fluids, hold your breath etc. Eye pressure fluctuates the same way as your blood pressure, so readings change from day to day, hour to hour and some people may naturally have a very low or high pressure. Therefore eye pressure reading alone cannot be the diagnosing factor.

Glaucoma Treatment

Glaucoma Treatment aims to prevent further damage to your sight. However, treatment cannot repair or reverse damage caused by eye pressure.

The main treatment is to reduce the pressure in your eye and/or improve the blood supply to the nerve.


Treatment to lower your eye pressure usually starts with eye drops. These glaucoma eye drops act by reducing the amount of aqueous humour produced by the ciliary body in the eyes or by opening up the drainage angle so excess aqueous fluid can drain away. In the majority of cases, the glaucoma eye drops lower your eye pressure and keep the eye pressure stable, which then protects your optic nerves against further damage and in turn prevents further sight loss.

Using your glaucoma eye drops as your ophthalmologist recommends is very important in stopping further vision loss even if you do not notice any difference.

If the drops do not lower eye pressure quickly enough or do not work as well as your ophthalmologist would like, multiple drops, laser or surgery may be indicated.

Laser treatment

There are two main types of laser surgery that can be used to control eye pressure:

Laser trabeculoplasty; helps to improve the drainage of aqueous humour fluid by the laser. The laser changes the trabecular meshwork tissue at the drainage angle to allow aqueous humour to drain away more efficiently

Laser iridotomy; a new small drainage channel is made at the top of the iris by laser, this forms a new permanent passage through which the aqueous fluid can flow through, the laser iridotomy helps the aqueous humour push the iris tissue backward, unblocking the drainage angle.

Both types of laser treatment reduce pressure and usually only need to be done once but sometimes they may need to be repeated, this procedure does not require a hospital stay. Glaucoma drops are normally used in conjunction with laser treatment to continue to keep the eye pressure stable.

Trabeculectomy surgery

If eye drops and laser treatment cannot lower your eye pressure and keep it stable then trabeculectomy surgery may be considered. This trabeculectomy is achieved by making a small channel through the internal sclera (white of the eye) and is covered by a thin flap door.  The aqueous humour then drains through the flap and channel to a bleb that sits under conjunctiva (clear layer that covers the outer sclera); it is well hidden by the eyelid. The trabeculectomy surgery reduces the eye pressure and prevents or slows further damage to the optic nerve and further loss of vision.

Treating acute closed angle glaucoma

If you are diagnosed and treated promptly, there may be almost complete and permanent recovery of vision. If you have an acute attack you will need to go into hospital immediately. You will be given intravenous medication (acetazolamide, glycerol), this will make your eyes produce less aqueous fluid which will allow easier drainage of the aqueous humour, lower the eye pressure and in turn help relieve the pain. Sometimes miotic eyes drops are given to help open up the drainage channel at the trabecular meshwork.

The Ophthalmologist will probably suggest a procedure called laser iridotomy; this makes a small drainage channel at the top of the iris to allow the aqueous humour fluid to drain away and will help the iris flatten unblocking the drainage angle. Usually you will have the laser iridotomy done on both eyes because there is a high risk that the other eye will develop the same problem. This treatment is not painful.

If the eye pressure still remains a little raised you may be treated with glaucoma eye drops.

Patients with very mild or no symptoms of acute closed angle glaucoma but with very narrow drainage angles maybe recommended glaucoma laser iridotomy surgery to prevent an acute attack.

Monitoring glaucoma

If you are diagnosed with glaucoma your ophthalmologist will start you on a treatment plan, make sure you are responding to the treatment and check that your eye pressure stays in the stable range. This may take a few visits in close succession.

If your eye pressure stabilises and you are not having any problems with treatment then you will be able to go for check-ups every six or 12 months.

It is very important that you attend all your appointments to make sure your eye pressure stays stable (as you may not notice any changes to the eye pressure), ensure your Glaucoma eye drops are working as you could lose more sight if your current treatment becomes ineffective.

On each visit, you will have the eye pressure measured in both eyes, your visual field will be intensively tested and the back of your eyes examined.

Most people with glaucoma use drops for many years of their lives. Using your glaucoma drops regularly can help to keep your eye pressure under control and minimise further damage to your sight. Not using your drops could make your glaucoma unstable and lead to permanent sight loss, which cannot be reversed.

Glaucoma support

You may find that you are anxious or worried about your eye condition and vision. These feelings are not invalid and support is available.

Help is available through your GP and the RNIB, which will provide emotional support alongside your family and friends. RNIB helpline 0303 123 9999


You are required by law to report a condition, which might affect your sight. Most patients with Glaucoma do carry on driving unless their glaucoma is particularly advanced. The DVLA may carry out regular tests to assess if it is safe for you to drive.

For more information, advice on common eye conditions, or to book an appointment at Eyedeal Vision please call 020 8524 2887 today and a member of the team will be happy to help you.