What is Glaucoma?
07 February 2019
Glaucoma is an eye condition that causes damage to the optic nerve (responsible for carrying information from the eye to the brain). Glaucoma occurs when there is a high amount of pressure inside the eye (intraocular pressure) due to the eye’s drainage system becoming clogged, so fluid cannot drain effectively. If glaucoma is left untreated it can result in complete vision loss.
In this article we will explore:
- Types of glaucoma
- What causes glaucoma
- The signs and symptoms of glaucoma
- How to test for glaucoma
- Glaucoma treatments
Types of glaucoma:
There are various types of glaucoma. The two most common types are known as open-angle and angle-closure. The ‘angle’ specified in both cases refer to the drainage angle inside the eye, that controls the outflow of fluid created in the eye.
Chronic (open-angle) glaucoma
Also known as primary glaucoma, this occurs when the fluid inside the eye drains too slowly, building up the pressure in the eye. It is the most common type of glaucoma and in fact is a leading cause of irreversible blindness worldwide.
Aging of the eyes drainage system is usually the culprit for chronic glaucoma. However, that’s not to say that young people can’t develop this type too.
Unlike acute glaucoma, it progresses gradually. Frustratingly, chronic glaucoma will progressively reduce peripheral vision (side vision) without other symptoms; often causing permanent damage before a diagnosis.
Acute (angle-closure) glaucoma
Also known as narrow-angle, this form of glaucoma develops when the drainage system of the eye becomes blocked; causing a sudden increase in pressure inside the eye.
Symptoms to look out for include abrupt eye pain, severe headaches, halos around lights, dilated pupils, red eyes, nausea and vomiting. Immediate medical assistance is required if these symptoms arise. If ignored, slight vision loss can occur with each ‘episode’.
This is a form of open-angle glaucoma and although the optic nerve is still damaged, pressure in the eye is normal.
Optometrists aren't sure why normal-tension glaucoma occurs. Theories have suggested that it may be due to the optic nerve becoming overly sensitive; explaining why even normal pressure levels cause damage. Another theory suggests that there isn't enough blood getting to your optic nerve.
Pigmentary is another form of open-angle glaucoma and one of the rarest. This type of glaucoma happens when the eye’s drainage channel becomes clogged.
This clogging is due to pigment cells breaking loose from the iris and scattering within the eye. This in turn upsets the normal flow of fluid within the eye, leading to a rise in pressure.
Symptoms generally stay dormant, although some pain and blurry vision may arise after exercise. Pigmentary glaucoma mainly affects men aged 30-40.
Glaucoma can be inherited at birth and is usually diagnosed within the first year. This is caused by incorrect development of the eye's drainage system prior to birth.
Parents with babies at high risk of glaucoma are advised to look out for a cloudy, white, hazy, enlarged or protruding eye in their child. Medical care should be sought after in these cases.
What causes glaucoma?
Glaucoma happens when there is a build-up of pressure inside the eye, as a consequence of fluid not draining sufficiently. It’s this intraocular pressure that causes damage to the optic nerve, potentially resulting in complete vision loss.
Medical professionals are unclear as to why this happens. However, there are risk factors associated with glaucoma, which make some people more susceptible.
- Around 1 in 50 people over 40 have chronic glaucoma, in Europe.
- East Asians, Africans, and those of Hispanic origin have a greater risk of developing glaucoma, compared to Caucasians.
- If your mother, father or sibling has glaucoma you are at a higher risk of developing the condition yourself. Free eye tests on the NHS are offered in these cases.
- Diabetes, a high minus prescription (short-sightedness), high blood-pressure, use of corticosteroids and eye injury can all heighten the chance of developing glaucoma.
With this said, it is imperative that you attend regular eye examinations in order to detect the condition early on.
What are the signs and symptoms of glaucoma?
Apart from the sudden on-set of symptoms related to acute glaucoma, as mentioned before, glaucoma usually does not accompany symptoms. Instead, it develops gradually, affecting peripheral vision first.
For this reason, sufferers often do not realise that they have glaucoma until they have partially or completely lost their sight- a vital reason to attend regular routine eye examinations.
The sudden symptoms that may take place include:
- Intense eye pain
- Nausea and/or vomiting
- Sore red eyes
- Severe headaches
- Sensitivity in and around the eyes
- Seeing coloured rings around bright lights
- Blurry vision
In all of these cases, medical help should be sought after.
How can you test for glaucoma?
Your optometrist will check for glaucoma during a routine eye examination. There are several methods for testing the prevalence of glaucoma. All of which are painless and quick.
The most common tests are:
- Tonometer: A tonometer measures the intraocular pressure inside the eye. During tonometry, eye drops are administered to numb the eye and then a small amount of pressure is applied via a puff of air.
- Ophthalmoscopy: During ophthalmoscopy the optic nerve is examined to check for damage. During this exam, eye drops are used to dilate the pupil so that the optometrist can see through the eye; to examine the shape and colour of the optic nerve.
- Perimetry: Perimetry is a test that produces a map of your complete field of vision. This optometrist can then determine whether vision has been affected by glaucoma. During the examination, patients are asked to look straight ahead and indicate when a moving light passes their peripheral (side) vision.
How is glaucoma treated?
Early diagnosis of glaucoma is vital for successful treatment. Treatment can't reverse any loss of vision, but it can prevent vision from regressing further. There are numerous methods an optometrist may use to manage glaucoma.
These treatments include eye drops, medicines, laser and surgery.
Open-angle glaucoma is typically treated with eye drops. Eye drops work by either reducing the formation of fluid in the eye or increasing its outflow. This ultimately lowers the pressure in the eye.
Laser surgery is usually offered if the drops do not help.
Some glaucoma sufferers will be prescribed tablets by their optometrist. Similarly to the eye drops, these are taken to control the amount of fluid the eye produces.
These medications are usually taken two to four times daily. Some patients experience a tingling feeling in their hands, feet and lips, nausea and tiredness.
Laser is a common treatment for glaucoma. Because there are a number of different types of glaucoma, there are also a number of different laser treatments available.
The two types of laser used to treat open-angle glaucoma are:
- Laser trabeculoplasty, which reduces the intraocular pressure by increasing outflow of fluid from the eye.
- Cyclophotocoagulation, used to decrease the formation of fluid in the eye.
The two types of laser used to treat angle-closure glaucoma are:
- Laser iridotomy, where a small hole is made in the iris, to improve fluid outflow.
- Iridoplasty, where the iris is tightened and the drainage angle opened.
Surgery is not usually the first port of call to treat glaucoma, however it will be considered if nothing else works.
The various types of surgery available include:
During trabeculectomy, a small incision will be made in the sclera (white part of the eye). The tissue inside the sclera is removed, to help the extra fluid drain out. Medicine is sometimes needed after surgery to prevent scar tissue from forming.
Drainage implant surgery
A glaucoma drainage implant is a tiny tube which is placed inside the eye to help fluid drain out, helping to lower eye pressure. The procedure is performed under anaesthetic; you can go home after surgery but you won’t be able to drive for 24 hours.
Electrocautery is less invasive as trabeculectomy or drainage implant surgery. During this procedure, a heat device called a Trabectome is used to create a small incision in the eye’s drainage tubes. It sends heat to the tissue inside the eye, easing excessive fluid build-up and pressure.
As with any eye procedure, your eyes may water, feel sore or look red following surgery. Vision will most likely be blurred; however this should only last a few weeks.
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