To understand primary open angle glaucoma, it’s useful to understand what glaucoma is and how drainage in the eye works.
Your eye pressure is controlled by watery fluid called aqueous humour, or just ‘aqueous’. Aqueous is made in a ring of tissue that sits behind the iris called the ciliary body. It then flows through the pupil and drains away through tiny channels called the trabecular meshwork.
The trabecular meshwork is found in the angle between the cornea and the iris (often called the drainage angle). In a normal eye, there is a balance between inflow and outflow of fluid, but in some eyes this balance is disturbed, and this causes the eye pressure to rise.
In most cases of POAG, the problem occurs due to the fluid outflow not working as well as it should. The eye can’t get rid of the fluid fast enough and the build-up results in increased eye pressure. The increase in pressure damages the optic nerve by reducing the amount of blood that can get through the tiny blood vessels and by pressing on the nerve itself.
Glaucoma cannot be cured, but it can be managed effectively. Sight loss resulting from glaucoma cannot be reversed, but with effective medical treatment, the damage can be slowed or even stopped in its tracks.
Anyone can develop primary open angle glaucoma but there are several risk factors which makes the onset of glaucoma more likely. These include.
Age – Primary open angle glaucoma becomes more common with age. Its uncommon below the age of 40 but the number of people with glaucoma rises from about two in 100 over the age of 40 to more than one in 20 for those aged 80+.
Ethnicity – People of African -Caribbean origin have about a four times increased risk of primary open angle glaucoma when compared to those of a European origin.
Family history – There is at least a four times increased risk of developing glaucoma if you have a close blood relative with the condition (mother, father, sister, brother, child). If you have glaucoma, you should tell your relatives about the condition as they may need to be tested. More information about ‘Glaucoma and your relatives’ can be found in our leaflet that can be downloaded or ordered here. Other risk factors include myopia (short sight) and corneal thickness.
POAG gives no warning symptoms in its early stages. There is no pain and in many cases, a person with this condition is completely unaware of the damage that is being done. This is because the typical damage occurs in the off-centre (peripheral) parts of the vision. Both eyes work together and one eye ‘fills in’ for the other so that blank patches are not noticed.
The aim of treating POAG is to reduce the pressure within the eye. By achieving this, it reduces pressure on the optic nerve and helps to stop further damage. Treatment is usually by eye drops. These help by reducing the fluid produced by the eye, increasing the drainage of fluid from the eye or both. You can find out more about eye drops here in our booklet ‘Eye drops and dispensing aids’ .
Laser is another common treatment and may be offered instead of, or in addition to eye drops.
If eye drops/ laser do not lower the eye pressure enough, surgical treatments are available.
Both PACG and POAG lead to an increase in eye pressure. The increase in pressure damages the optic nerve by reducing the amount of blood that can get through the tiny blood vessels and by pressing on the nerve itself.
To understand primary angle closure glaucoma, its useful to understand how fluid flows in and out the eye and how this is affected by reduced or narrow angles.
Your eye pressure is controlled by watery fluid called aqueous humour, or just ‘aqueous’. Aqueous is made in a ring of tissue that sits behind the iris called the ciliary body. It then flows through the pupil and drains away through tiny channels called the trabecular meshwork. The trabecular meshwork is found in the angle between the cornea and the iris (often called the drainage angle). If this drainage angle is narrow, this can reduce the effectiveness of fluid escaping the eye.
Some eyes naturally have a narrower drainage angle for example, people with smaller eyes, people who are long-sighted or people of particular ethnic origins. This smaller angle can slow down, or even close completely causing fluid to build up and eye pressure to rise.
PACG can be chronic or acute. Chronic angle closure develops slowly, usually without symptoms, as the drainage angle gets smaller and the eye pressure slowly rises. This is usually identified during a routine eye test at an optometrist. The eye doctor may use laser treatment to help prevent the narrow angle closing completely.
Anyone can develop primary angle closure glaucoma but there are several risk factors which makes the onset of glaucoma more likely. These include.
Age – Acute and chronic angle closure become much more common with increasing age. It is rarer below the age of 40.
Gender – Angle closure glaucoma affects women 50% more often than men.
Ethnicity – If you are of Asian origin, you are more at risk of angle closure glaucoma than someone of European origin. It may also come on at a younger age and be more severe.
Family history – Family members of those with angle closure glaucoma are 10 times more likely to develop it.
Primary angle closure is also more common in people with smaller eyes and those with long sight (hyperopia).
Acute primary angle closure, also known as ‘acute glaucoma ’ happens when a blockage is sudden and causes the pressure to rise very high, very quickly. Symptoms include intense pain, redness of the eye, blurred or reduced vision, headache and nausea. This tends to be very painful and it is vital that you seek medical advice immediately, as this sudden rise in eye pressure can cause permanent damage to your sight.
Sometimes, people get a series of mild attacks of angle closure. These are called ‘sub-acute’ attacks. Symptoms may include blurred vision, halos around lights and headaches. These attacks may come and go, but if this happens, it’s very important to seek immediate medical advice as it might be a warning of a future serious attack.
If you have narrow angles (where the cornea and iris meet), and are therefore at greater risk of developing PACG, this will be identified at a routine eye test.
Acute angle closure is initially treated with drops and an intravenous injection to lower the eye pressure. Once the pressure is lowered, a laser or surgical procedure is carried out in order to bypass the blockage in your eye’s drainage system and prevent it happening again.
Normally, the same procedure is also performed in the other eye in order to prevent an attack of acute angle closure in that eye. These treatments are not painful and are usually carried out as an out-patient, although a short stay in hospital may occasionally be required.
If primary angle closure is diagnosed and treated without delay there may be an almost complete and permanent restoration of vision. However, any delay in addressing the problem may result in permanent damage to the affected eye. Occasionally the pressure may remain raised and ongoing treatment will be required.
Chronic primary angle closure is treated in a similar way with drops to lower the pressure. In addition, laser treatment is often given to prevent further angle closure.
If you have been diagnosed with glaucoma and prescribed eye drops, it is very important that you put in your eye drops every day. Sometimes it can be difficult to get into a routine, or to get the drops in your eye.