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In most cases, but not always, glaucoma is associated with a rise in intraocular pressure (eye pressure). Intraocular pressure is generated through a balance between the production of aqueous fluid, which keeps the eye formed, and its outflow through the eye. It is measured using a number of different tools and these can be divided into non-contact, for example air puff tonometer, and contact, for example Goldmann applanation tonometer.

What is glaucoma?

Glaucoma is a family of disorders which if left untreated can cause progressive and irreversible damage to the optic nerve. The optic nerve is essentially the cable wire transferring visual information from the eye to the brain. The damage to the visual system tends to be in a characteristic pattern with a corresponding loss in visual field. It is the most common cause of irreversible blindness worldwide and by 2020, there will be an estimated 80 million people suffering with glaucoma.

Types of glaucoma

Glaucoma can be divided based on whether or not the drainage angle within the eye is open or closed as well as if there is a secondary cause for the glaucoma or not.

Open angle glaucoma:

This is the most common type of glaucoma. In most cases, the patient is asymptomatic and it is incidentally identified, often at a routine eye test. It can be associated with high eye pressure or normal eye pressure. This can be primary (without another identifiable cause) or secondary (due to other conditions such as pseudoexfoliation or pigment dispersion syndrome).

Closed Angle glaucoma:

This occurs due to the mechanical obstruction of the drainage angle and is associated with suddenly high eye pressure. Again, the cause for this can be primary (anatomically narrow angle) or secondary (for example diabetes, and previous inflammation). The eye pressure can suddenly rise and cause an attack of acute angle closure.

Causes of glaucoma

Causes of open angle glaucoma:

Primary open angle glaucoma is caused by raised eye pressure. If the eye pressure is higher than the expected average (10-24mmHg), it can over time compress the optic nerve, causing cell death which in time will lead to loss of visual field and developing glaucoma. In patients where the drainage angle is normal, the reason for the raised eye pressure is believed to be an imbalance in rate of the aqueous fluid production and drainage. This means that too much fluid is made and so there is a build-up of excess fluid in the eye which subsequently leads to the eye pressure to rise. Why some people have raised eye pressure remains unknown. It is thought to be multifactorial. The factors include positive family history (some genetic markers have been identified), age (more common in older patients), race (more common in Afro-Caribbeans), gender (more common in men) and systemic disease (for example high blood pressure).

Secondary open angle glaucoma is when certain conditions cause a rise in eye pressure with the angle remaining open, including:

  • Pigment dispersion syndrome: this condition occurs in low grade-medium myopic patients. The iris (coloured part of the eye) rubs against the natural lens and releases pigment. The pigment in turn migrates and blocks the drainage angle and so causes the eye pressure to rise.
  • Pseudoexfoliation: this is another hereditary condition where there is a gradual deposit of white flaky materials within the eye and in the angle which can lead to a rise in the eye pressure
  • Neovascularisation: abnormal blood vessels grow in the front part of the eye, again causing blockage of the drainage angle. The vessels can also bleed and the blood in turn blocks the angle and causes the pressure to rise
  • Uveitis and inflammation: white inflammatory cells fill the anterior chamber of the eye and cause obstruction of the outflow of the aqueous fluid
  • Iatrogenic & trauma: the use of certain elements during or after surgery can cause the eye pressure to rise. Namely, the use of tamponade gas or oil during retinal surgery. Trauma can cause mechanical damage to the drainage angle and subsequently cause the pressure to rise
  • Steroid response: 10% of the population are “steroid responders”, which means when they use any form of steroids (drops, cream, inhaler, tablets) the eye pressure rises. The pressure tends to return to normal within 6-8 weeks once the steroid agent is stopped

Causes of closed angle glaucoma:

Primary closed angle glaucoma is caused by narrow drainage angle. In some eyes, the reason for the raised eye pressure is that the drainage angle in the eye is narrow, which restricts the aqueous outflow and in turn causes the eye pressure to be high, leading eventually to glaucoma. In primary angle closure, the drainage angle would have been narrow from birth and this is usually only incidentally identified at a routine optician appointment. Having narrow angles if left untreated can cause an acute rise in the eye pressure and lead to what is known as acute angle closure glaucoma. Here, there is a sudden rise in the eye pressure which causes pain, redness, blurry vision and severe headaches and nausea. During an attack, the eye becomes red and the pupil (the black circle in the eye) can look distorted.

Secondary closed angle glaucoma can occur for the following reasons:

  • Phacomorphic: a growing cataract in time can completely block the drainage angle and cause a rise in the eye pressure. This is more common in patients who originally had a “small” or “short” eye and can occur very rapidly
  • Iatrogenic & trauma: again during intraocular surgery, the drainage angle can be closed off either secondary to an agent used during the surgery or after effects of it. Trauma can damage the lens and mechanically shift it to block the drainage angle and cause the eye pressure to rise

Eye close up


Symptoms of glaucoma

For the most part, glaucoma is asymptomatic as the build up of the eye pressure is so gradual. The visual field loss tends to affect the peripheral vision at the start and again this can go unnoticed for a long period of time. In angle closure however, because the pressure rise is very rapid, the patient does experience symptoms of red, painful eye, with blurred vision and halos around light. The pain can be very severe and cause headaches as well as vomiting. This is an ophthalmic emergency and would require immediate management.

Glaucoma prevention

Currently there is no option to reverse any sustained damage to the optic nerve from glaucoma. The nerve is an extension of the brain and so the tissue does not regenerate once it is lost. The recommendation is to detect glaucoma as early as possible and halt any disease progression. It is important to attend regular eye check ups so your optometrist can flag any glaucoma in its early stages and you can begin treatment. You should also be aware of your family’s eye health history as glaucoma can be hereditary. Your optometrist will normally ask if anyone in your family has glaucoma during check ups, so give them as much information as possible.

The other important step if you have been diagnosed with glaucoma is to attend at least annual appointments to monitor your eye pressure. Our yearly glaucoma care package costs £950 and covers a year of unlimited glaucoma consultations and diagnostics. Contact us today to find out more.

How is eye pressure measured?

There are two main methods used to measured eye pressure:

  1. Non-contact air puff tonometry. This is used by most high street opticians, but is not very accurate and can over estimate pressure.
  2. Goldmann contact tonometry. This is the most accurate form of contact measurement and is done by trained opticians and all ophthalmologists. The measurement is adjusted to the central corneal thickness as sometimes readings are falsely high due to a thick cornea, or vice versa.

Glaucoma assessment

As glaucoma is a progressive disease, normally, a series of examinations are required before a definitive diagnosis is made.

At the initial assessment, you will have a number of investigations, some of which will need to be repeated at every visit. A thorough medical history will be taken, and then you will undergo a slit lamp examination, first looking at the front segment of the eye, checking the intraocular pressure, assessing the drainage angle and looking for any secondary causes for glaucoma. If it is safe to do so, you will have dilating drops instilled to the eyes and the back (posterior segment) of the eye will be examined. You will also undergo imaging of the optic nerve to objectively assess the nerve fibre layer and keep an accurate record of the optic nerve status.

Finally, you may be asked to perform a visual field test that will show if there is damage to the vision.

The results of the examination and the glaucoma tests will then all be explained in detail and if the diagnosis of glaucoma is made, we can then proceed to talk about the various treatment options.


What questions will your doctor ask at a glaucoma assessment?

Alongside the physical examination, your doctor will also ask you some questions to understand your lifestyle and medical history. These are the top 10 questions they’re most likely to ask:

  1. Do you have any family history of glaucoma?
  2. Have you had any previous eye surgery? (including laser eye surgery)
  3. Have you had any previous trauma to either eye?
  4. Do you have any other ocular conditions?
  5. Do you have any symptoms of pain, redness or discomfort of the eye, with or without headaches or visual disturbance?
  6. What is your past medical history? (specifically diabetes, hypertension, renal conditions and asthma)
  7. What medication do you take regularly and do you have any known allergies?
  8. What is your occupation?
  9. Do you smoke?
  10. Do you drive?

Glaucoma treatment

Although we know high eye pressure is not the only cause of glaucoma, at present our only way to halt any further glaucoma damage is by controlling the pressure. All the different treatment modalities in principle work in 2 ways: decrease production of aqueous fluid or increase its outflow in order to lower the eye pressure.

There are a number of different options for treatment, including:

  • Topical treatment (eye drops). There are various drugs available which may be prescribed on their own or in combination. Most of these drops can cause side effects, so your consultant will discuss your best options with you
  • Oral medication. This is usually reserved for severe cases and for short term as long term it can affect both the liver and kidneys
  • Laser treatment. There are four main laser therapies available. The choice between them depends on the type of glaucoma the patient has (open or closed angle) as well as the severity of the disease
  • Surgical treatment. The different surgical options available effectively lower eye pressure by increasing outflow through a new channel. The different options are discussed with the patient and the appropriate treatment is selected.

Please read our glaucoma treatment page for more detail on the different treatments and surgeries available for treating glaucoma.

Ask the surgeon

Sally Ameen, cataract & glaucoma surgeon

Can eye drops affect the heart? Can they cause headaches? Yes, a specific group of drops (Beta blockers) can cause a number of systemic side effects. These include reducing both the heart rate and blood pressure. They can also cause headaches as well as sleep deprivation. One way to minimise the systemic effects of the eye drops is to reduce their absorption into the circulation. This can be done by pressing on the side of the nose next to the inner eye corner to block the tear duct immediately after the drop is installed. Then, the pressure can be removed after 20 seconds.

Sally Ameen

Glaucoma & cataract surgeon at OCL Vision
Meet Sally Ameen

More Glaucoma FAQs

Find out the answers to some more of the most frequently asked questions about glaucoma, from our expert surgeon Ms Sally Ameen.

Is glaucoma hereditary?

It can be. Research suggests that genetic and hereditary factors can increase not only the risk of developing glaucoma but the severity of the disease. Studies have shown those with a first-degree relative (parent or sibling) with glaucoma have an almost 10-fold risk of developing early onset glaucoma. There are a number of genetic mutations that have been identified, but it is felt there is still more to learn about the genetic makeup of glaucoma and how it is passed on.

What is the first sign of glaucoma?

In most cases, glaucoma does not cause any signs or symptoms in the early stages of the disease. This is why it is known as the thief of sight. For the most common type (primary open angle glaucoma), the eye pressure rise is so gradual that the patient remains asymptomatic and it is detected incidentally. As the disease progresses, the patient can develop a visual field defect, which is like an enlarged blind spot, where part of the vision is blurry or completely missing.

In a subgroup of glaucoma, the angle closure type, there is a sudden rise in the eye pressure, which can cause pain in the eye, redness, blurring of the vision as well as systemic signs like headache, nausea and vomiting.

Can glaucoma be cured?

Any damage to the vision from glaucoma whatever its subtype cannot be reversed. The optic nerve is an extension of the brain and it does not re-generate once lost. The treatments provided are to halt the disease progression as opposed to reverse it.

There is a subtype of glaucoma that can be “cured”: for patients where the cause of glaucoma is a narrow drainage angle, the condition can be indefinitely reversed following surgery. But again, if the nerve has already been damaged from glaucoma, even changing the drainage angle will not reverse this.

Can you drive with glaucoma?

The simple answer is yes. The DVLA have strict guidelines to follow and someone who is diagnosed with glaucoma undergoes annual assessment of their vision. The assessment includes visual acuity (sharpness) as well as a field of vision assessment that is performed with both eyes open and with the use of any correction to the vision needed. If the disease is too advanced at the time of diagnosis or continues to progress, then the person may be deemed unfit to drive. This decision is made by the DVLA and not your ophthalmologist based on their assessments that are performed at independent centres.

What does glaucoma vision look like?

Glaucoma affects “field of vision” and not “acuity” (until much later on in the disease). This means parts of the vision, usually the outer parts, are blurred or completely missing. This continues progressing and can leave the patient with only a central island of vision and if the disease is not halted, the vision can be lost completely and glaucoma will cause irreversible blindness.

Why take glaucoma eye drops at night?

There are a number of different groups of eye drops that can be used to control eye pressure. One of them (prostaglandin analogues) have been shown to be most effective if taken at night time. That would be the reason your ophthalmologist would recommend taking the medication at night time – to increase its effectiveness.

Are eye floaters a sign of glaucoma?

No, eye floaters usually occur to the ageing breakdown of the vitreous- the jelly cavity inside the eye. This is a natural ageing process that happens for most people and is not linked to glaucoma.