What is glaucoma?

Glaucoma is a common eye condition that affects the optic nerve, which carries information from the eye to the brain. It's caused by a build-up of pressure in the front part of the eye, which if left undiagnosed and untreated, could lead to loss of vision. Glaucoma is currently the second-leading cause of blindness worldwide, behind cataracts.

As most people won't experience symptoms (at least to begin with), the best way to detect glaucoma is by having your eyes tested regularly. During an eye test, the optician checks the overall health of your eyes - but also looks at the back, measuring pressure. That's why it's so important to be proactive with checking your eye health - opticians advise to have a routine eye test at least every 2 years.

Glaucoma causes

The eyeball constantly produces a fluid called aqueous humour, which normally finds its way around the eye, draining back into the body when there isn't any space left. But when the fluid isn't able to drain properly, it causes a build-up of pressure in the eye, known as intraocular pressure. In turn, that pressure damages the optic nerve, as well as the nerve fibres from the retina (the light-sensitive tissue that lines the back of the eye). If left untreated or uncontrolled, glaucoma starts by causing peripheral vision loss, which may gradually lead to blindness. You can see different levels of glaucoma and other eye conditions in this simulator created by Fight for Sight.

Glaucoma symptoms

Most cases of glaucoma are chronic, meaning it tends to develop slowly over the years, without showing any noticeable symptoms. It affects your peripheral vision first, working its way inward. Some people do experience mild symptoms, including blurred vision, or seeing rainbow-coloured circles around bright lights. Regular eye tests are the only way to stay on top of the condition and diagnose it before it reaches the centre of your vision when there's not much you can do.

Acute glaucoma works a little differently. It's not as common and could develop rapidly with a sudden and painful build-up of pressure in the eye. Unlike chronic glaucoma, you are likely to experience symptoms, including:

• Intense eye pain

• Redness in the eye

• Headaches

• Nausea and vomiting

• Tenderness around the eyes

• Seeing rings around lights

• Blurred vision

In this case, you'll need to get help as soon as possible so if your optician isn't free, call NHS 111, or your local Accident and Emergency department. Even if you go away, visit your optician as soon as you can, as chances are they might return.

Types of glaucoma

There are many different types of glaucoma, depending on the levels of pressure and the parts of the eye it affects. It also could be present in one or both eyes, to varying degrees. The most common is called primary open-angle glaucoma: it's caused by the gradual clogging that takes place in the drainage channels, though the liquid can still access the drainage angle as pressure builds up. Other types of glaucoma include:

• Acute angle-closure glaucoma, which is caused by a sudden blockage in the draining channels, raising the pressure within the eye really quickly.

• Secondary glaucoma, caused by an underlying eye condition, such as uveitis (inflammation of the eye).

• Developmental (congenital) glaucoma - a rare type that occurs in very young children and babies.

Who is at risk of developing glaucoma?

Glaucoma can occur for a number of reasons, but some factors can increase your risk of experiencing it such as:

• A history of the condition within your immediate family.

• Age: while children and young adults can also be affected by glaucoma, it affects 2 in every 100 people over 40.

• Medical conditions: diabetes, high blood pressure and heart disease could increase the risk of developing glaucoma.

• Other eye-related conditions: those with severe short-sightedness, retinal detachment, corneal ulcers, inflammations, raised eye pressure and physical injuries to the eye.

• Race: people of African, Caribbean or Asian origin are at a higher risk.

Diagnosing glaucoma

'The first signs of glaucoma usually appear on a regular eye test. During that, your optician will be looking at the overall health of your eye and using a tonometer, they will measure your intraocular pressure (IOP). Most tonometers simply send a puff of air into your eye's surface, while others work by numbing the eye with drops and rest a small probe gently against the surface.

If the tonometer detects your intraocular pressure to be higher than 21mmHg, your optician will then check for two things: is the eye producing too much fluid? Alternatively, is there a problem in the drainage channel? Then, depending on the findings, your optician would continue to treat you or refer you to a specialist optometrist, for additional diagnosis.

Other tests your optician might recommend include Perimetry (a visual field test that checks for missing areas of vision), Gonioscopy (an examination that focuses in the front part of your eye and can determine the angle of glaucoma) or Optic nerve assessment (taking a closer look to the responsiveness of the pupil).

Glaucoma treatment

'Vision loss that occurs by glaucoma can not be reversed, but treatment can help stop your vision from getting worse. The treatment that will be recommended to you will depend on the type of glaucoma you have, but the main options are:

• Eye drops that reduce the pressure in your eyes

• Laser treatment that opens up blocked drainage tubes, or reduces the production of fluid in your eyes

• Surgery that improves the drainage of the fluid

Eye drops are the most widely used treatment option for primary open-angle glaucoma, saving millions of people's vision around the world. But it's important to follow your optician's advice to the letter: not complying to prescribed glaucoma medication recommendations is one of the major reasons for glaucoma-caused blindness. If you find they are uncomfortable or inconvenient, consult your optician for an alternative, and only discontinue them once they recommend you one.

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What is glaucoma?

Glaucoma causes

Glaucoma symptoms

Types of glaucoma

Who is at risk of developing glaucoma?

Diagnosing glaucoma

Glaucoma treatment

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