Glaucoma is a condition many of us tend not to think about until it affects us or someone we know.
Nonetheless, it’s also a condition which can cause few or no early noticeable signs, and lead to irreversible damage if not acted upon.
With National Glaucoma Awareness Week just around the corner, we thought it might be useful to look into the condition in more detail; more particularly, what causes it, who is more likely to develop it, and what treatment options there are post-diagnosis.
In order to do so, we enlisted the help of Karen Brewer, spokesperson for the International Glaucoma Association.
The different types of Glaucoma
Karen describes four different types of glaucoma, which are:
Primary open angle glaucoma
This is the most common form, and is otherwise referred to as chronic open angle glaucoma. Primary instances are those not thought to be caused by another illness.
Karen explains that primary open angle glaucoma manifests slowly over time. Eye pressure (or intraocular eye pressure or IOP) gradually rises, eventually causing damage to the optic nerve.
The cause of this increase in pressure, Karen tells us, is usually because fluid in the eye is not able to drain out properly.
The optic nerve sustains damage when IOP restricts blood flow towards it, and this pressure also squeezes the actual nerve and inhibits its function.
Primary angle closure glaucoma
Karen explains that this occurs when the iris ‘blocks the drainage of the eye through the trabecular meshwork’. This meshwork is a section of tissue beneath the eye which acts a filter for aqueous humour (fluid in the eye).
This type of glaucoma can be acute or chronic in nature.
When it occurs acutely, drainage issues arise because the iris advances and creates a ‘closed angle’ at the bottom of the eye so that fluid cannot escape; in turn increasing eye pressure. Swift treatment is recommended to avoid permanent damage.
Chronic cases are caused by the same issue, although the development will be much slower and no noticeable symptoms may appear initially.
This is where an underlying medical condition causes eye pressure to build, resulting in either open or closed angle glaucoma.
Developmental (or congenital) glaucoma
This term is used to refer to those cases which develop during infancy or childhood, and includes primary congenital glaucoma, Axenfeld’s or Reiger’s Anomaly, and Peter’s Anomaly.
There are also other types of glaucoma which can come about as a result of cataract surgery, or tissue inflammation connected with arthritis.
Those more at risk of developing glaucoma include persons:
- over the age of 40. Karen explains that around two percent of people over 40 are affected, but this number increases with advancing age: the number of over 80s affected is around five percent;
- with low blood pressure in the eye;
- of African-Caribbean origin. The risk compared to those of European ethnicity is four times higher;
- of Asian origin;
- with a family history of the condition. Those with a first line relative who is affected are also thought to be four times as likely to develop glaucoma;
- who have long- or short-sightedness;
- with diabetes.
Glaucoma, left untreated, can lead to loss of sight, which is why early diagnosis and treatment is so key:
‘The vast majority of people diagnosed with glaucoma today will not go blind,’ Karen tells us, ‘but only if they adhere to the treatment regime prescribed by their glaucoma specialist, and attend their follow up appointments regularly.’
Early warning signs
- Primary open angle glaucoma, which develops slowly, might present no noticeable signs. Karen explains that the other eye may compensate for the damage being caused in some cases (by overworking to complete holes in vision) which can make noticing the problem difficult.
- Acute primary angle closure on the other hand, can cause significant pain because the increase in intraocular pressure occurs quickly. Visual disturbances such as halos and cloudiness may also occur, as might redeye and nausea.
- Less severe symptoms, or sub-acute attacks, may occur infrequently with angle closure. Someone’s sight may develop a mist or they may notice rings appearing around lights.
- If someone notices these signs, Karen explains, they should seek advice from an optometrist immediately.
- Cases of secondary glaucoma may not be identified until investigation of the primary condition causing it is being carried out.
- During the advanced stages of glaucoma, Karen illustrates that someone may still be able to read and interact with others as normal, but mobility may be an issue because the field of vision has been reduced. Reading and recognition capacity will inevitably diminish however if the condition is not treated.
- ‘In some,’ Karen adds, ‘there may be intermittent symptoms of eye ache with cloudy vision, where the vision becomes milky or hazy.’
- However, for most, it will not cause pain or any noticeable signs until it has developed to a significant stage. Regular eye checks, Karen explains, are therefore very important.
The three tests most commonly used to detect glaucoma don’t take very long to conduct:
- Ophthalmoscopy (this involves assessing the appearance of the optic nerve). Optometrists are now legally required to look at the back of the eye when conducting an eye check, where the optic nerve is located.
- Tonometry (where pressure in the eye is gauged). Persons who are at increased risk of glaucoma will need to have this check performed. Karen explains that this is undertaken with a tool which blows a very small puff of air into the eye.
- Perimetry (assessing the patient’s field of vision). Where the above investigations do not produce definitive results, an optometrist may also use this test.
In the UK, eye tests for those over 40 are provided for free, but Karen recommends that people should generally get tested earlier, particularly if they are at increased risk.
Karen explains that most cases of glaucoma can be medicated with eye drop treatment. A selection of different versions exist, but the aim of all them is to decrease IOP (your specialist or your GP will help you determine what the best option is). They are a maintenance treatment which will need to be used long term to keep IOP under control.
Where this treatment does not sufficiently lower IOP, a specialist may advise surgery:
This procedure involves ‘making small hole in the sclera’ Karen explains. A slender trap-door helps to drain excess fluid (aqueous humour) into a compartment concealed by the eyelid. The way this trap-door is fashioned enables it to flow out gradually. This then facilitates a decrease in eye pressure, and prevents the progression of glaucoma (however a trabeculectomy does not reverse damage already sustained to the eye).
Aqueous Shunt Implantation
This procedure again focuses on facilitating better fluid drainage from the eye to reduce IOP. The implant comprises a tiny silicone tube connected to a small plate which when in place sits on the white of the eye, underneath the eyelid, and acts as a reservoir for aqueous humour.
Aqueous shunts are sometimes referred to as tube implants or tube shunts. There are a few variations which may be used to help to offset very low eye pressure in the weeks following the procedure.
Much like the trabeculectomy, a shunt is not able to reverse damage to the optic nerve.
The two-year guideline
Getting tested regularly then is imperative in taking measures to prevent the buildup of IOP and reduce the likelihood of permanent damage to the eye.
As a guide, whether you fall into any of the above high risk groups or not, the NHS recommend getting an eye test every two years. During these tests, an optometrist will be able to spot any potential issues early and suggest action if necessary.
National Glaucoma Awareness Week runs from 6-12 June. You can find out more about the campaign (and more information on glaucoma) on the International Glaucoma Association website.