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Description

Glaucoma is the name for a group of conditions characterised by damage to the optic nerve caused by increased pressure within the eye (known as intraocular pressure) or weakness in the optic nerve itself.

Glaucoma may be broadly divided into 2 types: Open Angle and Angle Closure. ‘Angle’ refers to the location of the drainage mechanism, at the junction of the edge of the window of the eye (cornea) and the coloured part of the eye (the iris). Fluid which is produced behind the iris flows through the pupil into the space between the cornea and the iris (the anterior chamber) and is drained out of the eye through this drainage mechanism. This fluid circulation maintains the normal pressure within the eye.

In angle closure glaucoma access of fluid to this drainage mechanism is physically blocked resulting usually in a sudden, very often painful, rise of pressure within the eye requiring emergency treatment. In open angle glaucoma the fluid has full access to the drainage mechanism but the mechanism may be clogged. The rise in pressure occurs more slowly and the patient is often not aware of the rise. It is a lifelong condition which can give rise to vision loss and potentially blindness.

However, with early detection and treatment, such damage could be prevented. Open angle glaucoma is silent in its early stages and often doesn’t present many symptoms until vision loss is advanced and beyond repair. With our aging population, the number of people living in Ireland with glaucoma is expected to increase in the coming years.

Symptoms

Open Angle Glaucoma

Primary open angle glaucoma, is like a silent thief of vision. While your eye may seem perfectly normal, with no pain and no apparent change in your eyesight, over time your vision is actually being damaged behind the scenes.

In the early stages of this condition, there may be no symptoms at all. By the time symptoms appear, the condition can be quite advanced. Vision loss with chronic glaucoma can begin to affect a person’s peripheral (side) vision, although this may not be easily noticed. Individuals may notice that their vision is better in one eye over the other. Vision loss in the shape of an arc a little above and / or below the centre when looking ‘straight ahead’ may also appear. If glaucoma is left untreated, this area spreads both outwards and inwards.

The centre of the field is last affected so that eventually it becomes like looking through a long tube, so-called ‘tunnel vision’. In time even this sight would be lost.

Early symptoms of glaucoma may be detected at regular eye health check ups when the ophthalmologist can assess the pressure within the eye and image the optic disk at the back of the eye for glaucoma related changes.

Acute Angle Closure Glaucoma

Primary angle closure glaucoma or closed angle glaucoma, usually presents acutely with a sudden increase in eye pressure, which can be very painful.

For some people, this condition presents in a series of mild attacks, which often appear in the evening due to widening of the pupil in the reduced lighting. In the early stages an individual may notice misty rainbow coloured rings around white lights and there may be some discomfort in the eye. In other cases, this condition can rapidly cause the eye to become red, vision to deteriorate and may even cause a black out. There may also be nausea and vomiting.

Secondary Glaucoma

This type of glaucoma can present as a result of another eye condition or acquired as a result of another condition or medication. An example would be following an eye inflammation, known as uveitis. As such, the types of symptoms experienced with secondary glaucoma may vary depending on the original condition.

Frequently, this condition presents in one eye and not both, which is unlike other types of glaucoma. In the early stages of this condition, there may be no symptoms. With time, individuals may experience hazy or cloudy vision or eye discomfort.

In some susceptible individuals, open angle glaucoma may be caused by use, usually prolonged, of steroid eye drops. In people with a naturally shallow anterior chamber widening of the pupil by drops during an eye examination may result in closure of the drainage angle and result in acute glaucoma.

Developmental Glaucoma

This type of glaucoma presents in babies and young children. Symptoms experienced include larger than normal eyes, excessive tear levels or blinking, increased sensitivity to light and cloudiness of the cornea.

Causes

The visual symptoms of Glaucoma are caused by damage to the optic nerve when it comes under too much pressure. How much damage there is will depend on how much pressure there is and how long it has lasted, and whether there is a poor blood supply or other weakness of the optic nerve. A really high pressure will damage the optic nerve immediately. A lower level of pressure can cause damage more slowly, which would lead to a gradual loss of sight if not treated.

In most cases, the damage is caused by raised intraocular eye pressure. In other people however, the intraocular eye pressure is within normal limits but damage occurs because of a weakness in the optic nerve. In most cases both factors are involved but to a varying extent. Eye pressure is largely independent of blood pressure.

Chronic Glaucoma

This is the most common form of glaucoma, in which the aqueous fluid can get to the drainage channels (open angle) but they slowly become blocked over many years.

There are several factors which can increase the risk of developing chronic glaucoma. These include increasing age (over 40), having a family member with chronic glaucoma, high degree of short sightedness, diabetes, or ethnicity (African, Caribbean, Asian origin).

Acute Glaucoma

Acute glaucoma occurs when there is a sudden and complete blockage to the flow of aqueous humor out of the eye, causing a rapid increase in intraocular eye pressure. This is because a narrow “angle” between the iris and cornea (where the trabecular meshwork is located) closes to prevent the aqueous humor ever getting to the drainage channels. This is why acute glaucoma is sometimes called “closed angle glaucoma”. This can be quite painful and will cause permanent damage to sight if not treated promptly. People who are longsighted may be at increased risk of having a shallow anterior chamber and thus an increased risk of angle closure.

Acute glaucoma is much less common in western countries.

Secondary Glaucoma

Secondary glaucoma occurs as a result of the development of another eye problem, other medical condition or medication. This condition can present as either open angle or closed angle glaucoma. Pseudoexfoliative glaucoma is a form of glaucoma due to blockage of the drainage mechanism by dandruff-like particles. There is some evidence that Pseudoexfoliation Glaucoma may occur more frequently in Ireland. Other causes of secondary glaucoma include poorly controlled Diabetes Mellitus, inflammation within the eye (uveitis) or trauma.

Developmental Glaucoma

This rare but potentially serious condition in babies or children occurs where the eye’s drainage system does not develop correctly before birth.

Diagnosis

Glaucoma is diagnosed through a number of tests which are important for providing the correct diagnosis. As glaucoma becomes much more common over the age of 40, eye tests should be performed at least every two years, or as recommended by the eye care specialist, with all three glaucoma tests. All these tests are very straightforward, don’t hurt and can be done by most high street optometrists (opticians). This has been shown to be much more effective in detecting glaucoma than just having one or two of the tests. These tests are:

Eye pressure test: Measuring the pressure in the eye using a special instrument (tonometer). This may be done using a puff of air or by an instrument gently touching the numbed cornea.

Visual field test: Being shown a sequence of spots of light on a screen and asked to identify them

Optic Nerve Test: Viewing the optic nerve by shining a light from a special electric torch into the eye

If glaucoma is suspected, an individual will be referred to an ophthalmologist for a more detailed diagnosis and management plan.

The ophthalmologist will ask about a person’s medical history, including any family history of eye conditions. Individuals will receive a clinical eye examination where they may be asked to read letters off a chart (Snellen chart). They will also check intraocular pressure and examine visual field. The eye doctor will examine the area between the cornea and the iris where the aqueous humor exits the eye, to see if the angle between both parts of the eye is open or narrowed / blocked

Measurement of the thickness of the cornea might be done as this can impact how intraocular pressure is evaluated. A thicker cornea may mean that a higher pressure reading can be tolerated before pressure lowering treatment is required.

Optical coherence tomography (OCT) can also be used to assess the various layers at the back of the eye to see if loss of the nerve fibres on the top of the retina has occurred. This test can be very informative in assessing response to treatment.

Treatment

At present, established vision loss caused by glaucoma cannot be treated or cured. Instead, the focus is placed on early diagnosis and prevention and on ensuring that the intraocular pressure is kept under control and within normal levels. The ophthalmologist will provide the best options for treatment in each particular case.

Early detection and treatment will usually prevent further damage by glaucoma. Much can be done to help use the remaining vision as fully as possible. Individuals should ask their optician or optometrist about low vision aids and whether they are eligible to register as partially sighted or blind.

Chronic Glaucoma

The main treatment for chronic glaucoma aims to reduce the intraocular pressure in the eye. Some treatments also aim to improve the blood supply to the optic nerve. Visits to the hospital may be required for treatment and regular check-ups afterwards.

Treatment to lower the intraocular eye pressure is usually started with eye drops. These act by reducing the amount of fluid produced in the eye or by opening up the drainage channels so that excess liquid can drain away. There are four major types of eye drops; prostaglandin analogues (increases clearance of aqueous humor out of the eye), beta blockers (slow production of aqueous humor), carbonic anhydrase inhibitors (reduce production of aqueous humor) and sympathomimetics (reduce rate of production of and increase clearance of aqueous humor).

If eye drops fail to provide sufficient benefit, the ophthalmologist may suggest either laser treatment or a surgical operation to improve the drainage of fluids from the eye. The laser treatment, known as laser trabeculoplasty, uses high energy beams of light to open up the drainage channels in the trabecular meshwork and allow for increased clearance of aqueous humor. This should help to decrease intraocular eye pressure. Surgical intervention is another treatment option for chronic glaucoma. A trabeculectomy, which is the most common type of surgical procedure for this condition involves removing a section of the trabecular meshwork to increase the flow of aqueous humor out of the eye.

Although damage already done cannot be repaired, with early diagnosis and careful regular observation and treatment, damage can usually be kept to a minimum, and good vision can be enjoyed indefinitely.

Acute Glaucoma

If an individual has an acute attack, they will require immediate hospital treatment so that the pain and the pressure in the eye can be relieved.

Drugs will be given which both reduce the production of aqueous liquid in the eye and improve its drainage. These include medications to reduce production of fluid in the front of the eye, given both orally and by eye drops to constrict the pupil of the eye (open the drainage angle allowing aqueous humor to be cleared out of the eye).

When the pain and inflammation have gone down, the eye surgeon will advise making a small hole in the outer border of the iris to relieve the obstruction, allowing the aqueous humor to drain away. This is usually done by laser treatment or by a small operation. Usually the surgeon will also advise the same treatment for the other eye, because there is a high risk that it will develop the same problem. This treatment is not painful. Depending on circumstances and the response to treatment, it may not require admission to hospital. In other cases, a short stay in hospital may be advised.

An acute attack, if treated early, can usually be brought under control in a few hours and can bring about an almost complete recovery of vision. Any delay to treatment could risk the loss of sight in the affected eye. Closed angle glaucoma may also take a more chronic course and may respond to treatments outlined above for other chronic forms of Glaucoma.

Secondary Glaucoma

The treatment for secondary glaucoma may vary depending on the original source of the condition, (another eye issue, another condition or medication). The options for reducing intraocular eye pressure include medications, laser treatment or surgery.

Eye drops to treat glaucoma act by reducing the amount of fluid produced in the eye or by opening up the drainage channels so that excess liquid can drain away. There are four major types of eye drops; prostaglandin analogues (increases clearance of aqueous humor out of the eye), beta blockers (slow production of aqueous humour), carbonic anhydrase inhibitors (reduce production of aqueous humor) and sympathomimetics (reduce rate of production of and increase clearance of aqueous humor).

If eye drops fail to provide sufficient benefit, the ophthalmologist may suggest either laser treatment or a surgical operation to improve the drainage of fluids from the eye. The laser treatment, known as laser trabeculoplasty, uses high energy beams of light to open up the drainage channels in the trabecular meshwork and allow for increased clearance of aqueous humor. This should help to decrease intraocular eye pressure. Surgical intervention is another treatment option for chronic glaucoma. A trabeculectomy, which is the most common type of surgical procedure for this condition involves removing a section of the trabecular meshwork to increase the flow of aqueous humor out of the eye.

Developmental Glaucoma

There may be a number of treatment options available for developmental glaucoma, depending on the presentation of the condition. Microsurgery, as well as other treatment options used to treat other types of glaucoma may also provide benefit. These options include eye drops, laser and surgery.

Eye drops to treat glaucoma act by reducing the amount of fluid produced in the eye or by opening up the drainage channels so that excess liquid can drain away. There are four major types of eye drops; prostaglandin analogues (increases clearance of aqueous humor out of the eye), beta blockers (slow production of aqueous humor), carbonic anhydrase inhibitors (reduce production of aqueous humor) and sympathomimetics (reduce rate of production of and increase clearance of aqueous humor).

If eye drops fail to provide sufficient benefit, the ophthalmologist may suggest either laser treatment or a surgical operation to improve the drainage of fluids from the eye. The laser treatment, known as laser trabeculoplasty, uses high energy beams of light to open up the drainage channels in the trabecular meshwork and allow for increased clearance of aqueous humor. This should help to decrease intraocular eye pressure. Surgical intervention is another treatment option for chronic glaucoma.

A trabeculectomy, which is the most common type of surgical procedure for this condition involves removing a section of the trabecular meshwork to increase the flow of aqueous humor out of the eye.

General eye check-ups are important for people living with Glaucoma, as these individuals may still be at risk of developing other kinds of eye problems that affect the general population, some of which may be treatable.

No matter what level of vision a person may have, it is important to look after the eyes. To find out more about what can be done to take care of the eyes on a daily basis, please visit our Tips for Good Eye Health.

Research

Researchers are making advances in understanding this condition in more detail. This work will assist efforts to develop therapeutics which will complement the treatments available currently and potentially help to target glaucoma more effectively.

Researchers are continuing to look for ways to decrease intraocular eye pressure, the cause of most cases of glaucoma. As is already known, there are a number of ways in which this pressure can be lowered, such as by reducing production of aqueous humor or by increasing clearance through the drainage channels. Such techniques are constantly being reviewed to identify better options, whilst newer alternatives are also being explored.

Researchers are developing and investigating implants which can be inserted into the eye to assist with aqueous humor clearance. A number of clinical trials are investigating the safety and efficacy of such implants. One clinical trial is due to examine a new way to drain away aqueous humor. The aim is to create a new drainage channels through areas of the retina damaged by glaucoma to decrease intraocular pressure.

Another area of interest is in the compliance of individuals in taking their medication as recommended by their eye care professional. Unfortunately, if the eye drops are not taken as directed, their ability to lower intraocular pressure may not be as effective as it could be. Researchers are investigating ways to ensure that individuals receive the correct dosage of eye drop when required.

Stem cells are another area of investigation. Stem cells are like precursor cells which have the potential to self-renew and generate many different types of cells. Bone marrow derived stem cells are being investigated in a clinical trial for glaucoma which is currently ongoing. Stem cell research for Glaucoma is still at an early stage and much more scientific investigation will be required before we know how effective it might be in human patients.

Information about clinical trials can be found on their website and can be searched by condition and trial location.

For further information, please contact the Research Department on 01 6789004.

Support

Receiving a diagnosis can be overwhelming for anyone, but this is not a journey that you have to make alone. There are many groups and resources available to provide support for people living with Glaucoma.

Fighting Blindness offers a free and confidential counselling service (Insight Counselling). For further information please contact insight@fightingblindness.ie or call 01 6746496.

A mindfulness group is also available on every Wednesday at the Fighting Blindness office at 11am.

For technology support and guidance, the Dublin-based Technology Exchange Club meets every Monday at the Fighting Blindness office at 11am. Another Technology Exchange Club, based in Cork, meet every Saturday in the Cork City Library, Grand Parade, Cork City at 11am. The Cork-based club do not meet on Bank Holiday weekends or on the second Saturday of the month. For further information please contact insight@fightingblindness.ie or call 01 6746496.

In terms of driving, most people can still drive if the loss of visual field is not advanced, however discussions with the eye doctor will provide greater guidance. To assess possible damage to peripheral vision, an individual will need a special test to see whether their sight meets the standards of the Driver and Vehicle Licensing Authority.

Resources

Féach provides support for parents of children living with sight loss in Ireland.

ChildVision is the national education centre for children with sight loss in Ireland.

NCBI (National Council for the Blind in Ireland) provides support and services for people living with sight loss in Ireland.

Irish Guide Dogs for the blind helps individuals and their families to achieve improved mobility and independence.

 

 

Last Updated: 4th March 2019