What is glaucoma?

Glaucoma is a group of eye diseases that damage the optic nerve. It often affects both eyes, usually to varying degrees. As most cases won’t have any symptoms, one of the best ways to detect glaucoma is during a routine eye test – that’s why it’s so important to have one regularly.

What causes glaucoma?

The eyeball contains a fluid called aqueous humour, which is constantly produced by the eye. Any excess fluid is drained from the eye through tiny channels and tubes. When the fluid cannot drain properly, pressure builds up in the eye.

Glaucoma typically develops when this increased pressure damages the optic nerve, which connects the eye to the brain, and harms the nerve fibres from the retina, the light-sensitive nerve tissue that lines the back of the eye.

In acute glaucoma cases this pressure rises rapidly to higher levels, even causing pain.

Risk factors of glaucoma

Anyone can develop glaucoma, but there are several risk factors which make developing it more likely.

  • Your risk of developing glaucoma is four times higher if you have a close blood relative who has it
  • Age plays a big part. Chronic glaucoma affects up to two in every 100 people over the age of 40 and around five in every 100 people over 80
  • Higher levels of short-sightedness are linked to the chronic form of glaucoma, and long-sightedness to the acute form
  • Consistently raised pressure in the eye, called ocular hypertension (OHT), is a risk factor
  • People of African-Caribbean origin have about a four-times higher risk of developing chronic forms of glaucoma compared to those of European origin
  • Acute glaucoma is generally much less common, however people of Asian origin are at higher risk of developing this type of glaucoma compared with those from other ethnic groups
  • People with diabetes may be at higher risk of developing glaucoma
  • Very high blood pressure can lead to an increase in intraocular pressure, which can increase your risk of developing glaucoma
  • Low blood pressure can lead to insufficient blood supply to the optic nerve, which can also cause problems
  • Eye conditions, surgeries or injuries: injury to the eye can cause secondary open-angle glaucoma, either immediately after the injury or some years later
  • Regular users of steroids are at higher risk of developing glaucoma

High intraocular pressure

Everyone has fluid inside their eyes that is regulated by tiny tubes and drainage channels in the eye. Sometimes these channels don’t work as well as they should or can become blocked, and this can cause the pressure in the eye (intraocular pressure) to rise.

A high intraocular pressure can be a significant risk factor in developing glaucoma. If the pressure is consistently high, it can start to affect the sensitive nerve fibres at the back of the eye. 

That’s why having regular eye tests is so important – it means we can keep an eye on your pressure levels every time you see us, along with all the other eye health checks we carry out.

Types of glaucoma

The main types of glaucoma are as follows:

Chronic or primary open-angle glaucoma

Chronic or primary open-angle glaucoma is the most common type of glaucoma. It develops gradually and painlessly, so an eye test is usually the only way to detect it.

Primary angle-closure glaucoma

Sometimes known as acute glaucoma, primary angle-closure glaucoma is usually treated as a medical emergency.

This is because, unlike chronic open-angle glaucoma, primary angle-closure glaucoma happens quickly due to a sudden rise in eye pressure, and if it’s not treated quickly, it can lead to sight loss.

Traumatic glaucoma

Traumatic glaucoma can develop after an eye injury – either a blunt trauma or something that penetrates the eye. It can happen either at the time of the injury or some time later.

Hereditary glaucoma

Is glaucoma hereditary?

There is at least a four-times higher risk of developing glaucoma if you have a close blood relative who has it. 

Studies(6) have shown that if members of your immediate family (a parent or a sibling) have glaucoma, your risk of developing early-onset glaucoma increases by almost 10 times. Your risk of developing glaucoma also increases if you have an identical twin who has the condition.

Congenital glaucoma

Congenital means a condition is present at birth and congenital glaucoma does affect a very small number of babies. The onset of congenital glaucoma happens before the age of three and is caused by mutations in two genes (CYP1B1 or LTBP2). 

These genes are inherited as an autosomal recessive trait, where both parents are carriers of the mutation but do not have glaucoma themselves. Their children can inherit both copies of the mutation, one from each parent, leading to the development of glaucoma.

What are the symptoms of congenital glaucoma?

Some of the signs of possible eye trouble in children can be difficult to spot. For childhood glaucoma, symptoms may include:

  • Unusually large eyes due to increased pressure
  • The cornea (the transparent front section of the eye) may appear cloudy
  • The child may display excessive tearing and photosensitivity, like closing one or both eyes in bright conditions
  • There may be signs and symptoms that indicate poor peripheral (side) vision, for example running or bumping into objects
  • Some children with childhood glaucoma may complain of discomfort or pain in the eye if there is a rapid increase in intraocular pressure
  • Babies with this condition may become irritable and refuse to feed(7)

Developmental glaucoma

Developmental glaucoma is another type of childhood glaucoma that appears between the ages of 10 and 20 years. It is associated with mutations in genes involved in the development of the eye — particularly in the front part of the eye and in structures that drain fluid from the eye. 

These developmental issues are usually inherited from one of the parents who is carrying a dominant gene, and may be associated with other developmental anomalies. For example, someone with developmental glaucoma may also have abnormal teeth or hearing loss.

Myocilin mutations

People diagnosed with glaucoma before the age of 35 may have a form of glaucoma associated with a mutation in a myocilin gene. Mutations in this gene are also inherited as autosomal dominant traits, meaning there’s a chance that parents with this form of glaucoma could pass it on to half of their children.

However, any form of glaucoma can have multiple gene variants that can place you in the risk group. It’s also important to note that even if someone in your immediate family has glaucoma, it doesn’t necessarily mean you will develop it yourself.

What are the symptoms of glaucoma?

There are various types of glaucoma and symptoms will differ depending on which type you have.

If you have chronic glaucoma, you might not realise you have it because it’s painless and affects your peripheral (outer) vision. Without regular checks you may not notice there’s a problem until your start to lose your more central vision.

Acute glaucoma develops much faster as a result of sudden pressure build-up in the eye. Although rare, it is usually painful and is often accompanied by:

  • Blurred vision
  • Haloes around lights
  • Headache
  • A red eye
  • Nausea/vomiting

If you get these symptoms, it is important to seek immediate assistance. Contact your optician or local accident and emergency department.

Even if the symptoms go away you should contact your optician as soon as possible as repeat episodes can cause damage to your eyesight.

How will glaucoma affect my vision?

Many people with early-stage glaucoma have enough vision to work, read, drive, and live independently. However, if you’ve been diagnosed with glaucoma, it’s important to use the eye drops you’ve been prescribed exactly as instructed. 

Neglecting treatment, including missing medications, can make your vision worse, and in some cases can even lead to vision loss(8).

Diagnosing glaucoma

Glaucoma will usually be diagnosed during a normal eye test. As well as looking at the overall health of your eye and the structures within it, you’ll have a series of quick and painless tests that help to spot any signs of glaucoma.

Tests for glaucoma

A glaucoma test is a series of medical evaluations performed to detect and diagnose glaucoma. The most common glaucoma test is the eye pressure test. Other glaucoma tests include the visual field test, digital retinal photography and optic nerve assessment.

Eye pressure test (tonometry)

An instrument called a tonometer is used to measure the pressure inside your eye – the intraocular pressure. 

Tonometry can be useful in identifying ocular hypertension (OHT – raised pressure in the eye), which is a risk factor for chronic open-angle glaucoma.

Other forms of tonometry might be used that measure eye pressure differently, for example by using drops and a probe.

Visual field test

You will be shown a sequence of light spots and asked which ones you can see. 

Some dots will appear in your peripheral vision, which is where glaucoma begins.

If you can’t see the spots in your peripheral vision, it may indicate the glaucoma has damaged your vision.

Digital retinal photography

This involves taking a picture of your eye with a specialist camera that gives the optician a good view of the retina and your optic nerve at the back of the eye.

Your optician will pay special attention to the optic nerve, as that’s typically where glaucoma presents itself. 

The images from your previous visits are compared against the current appearance of the eye to check for any changes that may indicate glaucoma.

Optic nerve assessment

Your optic nerve connects your eye to your brain. This can be assessed in a variety of ways during your examination and it is also photographed using a retinal camera. 

Digital retinal photography (DRP) captures an image of your optic nerve which can be used as reference for future visits and to track any changes that may occur over time.

Glaucoma treatment

Glaucoma can be treated but early detection is important. If left untreated, glaucoma can cause visual impairment and damage that cannot be reversed. But if it’s detected and treated early enough, further damage to vision can be minimised or prevented.

So regular eye tests are essential. You should have an eye test at least every two years or more frequently if advised by your optometrist. For example, they may suggest you have more frequent eye tests if you have a close relative with glaucoma, such as a parent, brother or sister.

If your optometrist suspects glaucoma, you will be referred to an ophthalmologist for further tests. If the ophthalmologist confirms a diagnosis of glaucoma, they will also be able to explain:

  • How far the condition has developed
  • How much damage the glaucoma has had on your eyes
  • What may have caused the glaucoma

They will then be able to advise on initial treatment which is either selective laser trabeculoplasty (SLT) or an eye drop used on a daily basis coupled with regular follow-up appointments, depending on which your ophthalmologist feels is most suitable to you.

Drops may be used to examine your eyes in a glaucoma appointment – these can temporarily affect your vision. 

Please check when making the appointment if you will be able to drive immediately after the appointment.

When will treatment start? How long will it last?

Glaucoma is a lifelong disease that progresses slowly, and treatment usually begins soon after the diagnosis is made.

The recommended initial treatment for glaucoma is selective laser trabeculoplasty (SLT), which is more effective with slightly slower estimated progression rates than eye drops. In addition, SLT can delay the need for eye drops and reduce the chance of needing them at all.31 

However, if you choose not to have 360° SLT or if laser treatment is not suitable due to other conditions, eye drop treatment may be recommended to you by your ophthalmologist. Treatment may be started in one eye first. This is typically the ‘worse’ eye, with the higher intraocular pressure, where a single drug may be tried to see if it works.

Eye drop installation technique will also be demonstrated to ensure you understand how to prescribe the medication. Later, your doctor may test different combinations of medications to find a solution that works best for you.

Regular follow-ups with your doctor are required while being treated with glaucoma eye drop medication. This helps your doctor to detect any progression of the disease promptly. If your vision is found to be worsening despite treatment, you may need an increased dose of your current medication or to change the medication that you’re taking. You may also be recommended for surgery. Stable patients are usually examined at three to six month intervals depending on the severity of the disease and the rate that it is progressing.(12)

Can glaucoma treatment affect cataracts?

Cataracts are not treated using medication, but eye drops for glaucoma can occasionally cause issues if you have cataracts. Some glaucoma eye drops make the pupil larger and can give someone with cataracts increased problems with glare. Other eye drops can make the pupil smaller, which allows less light into the eye – for someone who also has cataracts, this can cause a drop in the level of vision.

If you notice problems with glare, or with how much you can see, after starting eye drops for glaucoma, it’s important to talk to your ophthalmologist. If you have both conditions and need surgery, your ophthalmologist’s priority will be to control the glaucoma first, which may be with medication or surgery. If you need surgery for both glaucoma and cataracts, your ophthalmologist will advise whether it would be best to do both at the same time or one followed by the other.

Glaucoma eye drops

If you decide against SLT, your ophthalmologist will suggest using eye drops as a treatment. The purpose of the eye drops is to lower the eye pressure, either by reducing the amount of fluid (aqueous humour) that is produced or by helping it to drain better from the eye.

How do eye drops treat glaucoma?

This is dependent on the type of glaucoma. Some eye drops do both, and, sometimes, doctors can prescribe a combination of eye drops to reduce the risk of vision loss or to try and stop vision getting any worse. In addition to providing more effective treatment, another combination of eye drops may be given to reduce side effects.

How to administer eye drops for glaucoma?

It’s important that you administer the eye drops correctly for your glaucoma treatment correctly, to make sure the medication is fully effective. While the number of drops you use may vary depending on the medication you’ve been prescribed, the process for administering them is usually the same.

Firstly, you should make sure you face the ceiling when putting your drops in — you can do this by tilting your head right back, or it might be easier to administer your drops by lying down. When you have the eye drops ready and your head is tilted back, you can administer them, using as many the number of drops you’ve been as prescribed. 

Once administered, you should then apply pressure to the inner corner of your eye, where the tear ducts are. Hold your finger there for several seconds after instilling putting the drops in. This ensures that the medication doesn’t not drain away by the ducts, and allows the drops to be effective.

Prostaglandin analogues

Prostaglandin analogues (PGAs) are usually the first type of glaucoma treatment recommended by doctors. This is because they are effective at reducing IOP, have an easy once-daily dosage, and minimal side effects.(13)

What are prostaglandin analogues?

PGAs are a synthetic version of the body’s natural compound, and come in the form of eye drops. 

It’s the eye drop that binds to the receptor in order to stimulate the desired effect and help drain the fluid efficiently.

Types of prostaglandins used to treat glaucoma

Currently, there are four different types of prostaglandin analogue glaucoma eye drops available for glaucoma treatment in the UK:

  • Latanoprost
  • Travoprost
  • Bimatoprost
  • Tafluprost

Typically, these medications are used to help reduce IOP in people with open-angle glaucoma or ocular hypertension.

Latanoprost was the first PGA eye drop developed to lower IOP, and remains the most commonly prescribed.

Are there any common side effects for PGAs?

Generally, all of the PGAs mentioned above share some common side effects, however these tend to be localised to the eyes:

  • Dry eyes
  • Red (stinging) eyes
  • Increased pigmentation of the iris

It’s usually recommended that if you are pregnant or breastfeeding you do not take any PGAs for glaucoma treatment.(15,16,17,18) If you are suffering from any side effects, contact your ophthalmologist as they will be able to analyse why you might be responding to a specific PGA in a certain way and can adjust your treatment plan accordingly.

Combination therapy with prostaglandin analogues

Although PGAs are considered the most effective class of drug for reducing IOP, they are frequently combined with other medications such as beta blockers, adrenergic agonists or carbonic anhydrase inhibitors for increasing the efficacy of treatment. Studies have shown that the fixed combinations are as effective as individual medications administered separately.(19)

Laser treatment

Depending on the type of glaucoma, different types of laser treatment can be effective. In an acute case, a procedure called an iridotomy is often used to quickly relieve the pressure and keep it lower. In non-acute cases, a selective laser trabeculoplasty (SLT) can be used to help lower the pressure – this is especially useful for people with open-angle glaucoma who have tried eye drops to lower the pressure, but they haven’t worked.

Selective Laser Trabeculoplasty (SLT)

A selective laser trabeculoplasty is usually recommended for people with open-angle glaucoma.(22) In a laser procedure, SLT reduces intraocular pressure by increasing aqueous outflow through the trabecular meshwork. This, in turn, helps reduce intraocular pressure and prevent or slow down further vision loss in glaucoma patients.

SLT has minimal recovery time, is comparable to medical treatment, and can even delay or prevent the need for eye drops - thus avoiding the associated side-effects. Importantly, the effect of SLT is not permanent, but the procedure can be repeated.

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