What is glaucoma?
Glaucoma is an eye condition where the optic nerve is damaged by the pressure of the fluid inside the eye.This may be because the eye pressure is higher than normal, or because of a weakness to the optic nerve.
The anterior chamber of the eye (the inside of the front of the eye) is filled with a watery fluid called the aqueous humour. This fluid creates a pressure in the eye, which keeps it healthy and in the right shape. The eye pressure is known as the intraocular pressure (IOP) and it isn’t connected to the blood pressure in any way. The aqueous fluid, which is inside the eye, is different from tears.
The normal range of eye pressure is roughly around 10 to 21mmHg (mmHg stands for millimetres of mercury and is the measurement used for eye pressure).
If the fluid cannot leave the eye as quickly as it’s produced, the eye pressure will build up. This pressure can cause damage to the optic nerve at the point where it leaves the back of the eye. This damage is called glaucoma.
Research shows that close relatives of those who suffer from glaucoma are up to four times more likely to develop the disease than those without a family history of the sight-threatening condition. Early detection means the condition can be monitored and future damage to vision minimised, which is why it is important to schedule eye tests, especially if siblings or parents have glaucoma.
Types Of Glaucoma
1.Primary open angle glaucoma
The damage to the optic nerve occurs slowly over a long period of time due to the eye pressure increasing to more than 21mmHg.
This is the most common type of glaucoma in the UK. It’s also known as chronic open angle glaucoma.
A difference may be noticed in the vision because glaucoma affects the peripheral (side) vision first. As the peripheral vision is not as sensitive as the central vision, it’s difficult to notice any early changes – but the sight is being damaged.
As the problem might not be noticed until glaucoma is more advanced, it’s important to have regular eye tests.
Affect to the sight
Affects both eyes, but one eye may be affected more than the other.
Blind spots can begin to form in the outer edges of the vision
You may miss things in your side vision
Without treatment, sight loss can slowly progress so that the field of vision becomes very narrow and it can appear as if looking through a tunnel. Finally, if left untreated, the central vision may be affected too, causing blind spots to appear when looking straight ahead.
All treatment for glaucoma aims to lower the eye pressure to prevent damage to your optic nerve and your sight. Even if the eye pressure is at a normal level to begin with, treatment will still be aimed at lowering it to a level which is safe – the ophthalmologist may call this the ‘target eye pressure’.
Eye drops - Treatment to lower the eye pressure usually starts with eye drops, and for most people this is all the treatment they will ever need. But, these drops will need to be taken long term or for life. Taking the drops will not cause any change in the sight, but are preventing any future damage so it’s very important to keep taking them.
Laser treatment - If it’s not possible to control the eye pressure with eye drops alone, the ophthalmologist may suggest laser treatment. The most common treatment is called a laser trabeculoplasty. Laser treatments are generally straightforward procedures usually done in the outpatient clinic under local anaesthetic, and most people recover very quickly. The use of eye drops after the treatment is usually still requires to keep your eye pressure stable.
Surgery - In a very small number of people with glaucoma eye drops or laser treatments aren’t successful in keeping the eye pressure stable. In these cases, surgery may be an option. The most common surgery for glaucoma is called a trabeculectomy. This surgery creates a new permanent drainage channel in the eye for the aqueous fluid to drain away, lowering the eye pressure. The new opening is made in the sclera (also known as the white of the eye). The aqueous fluid drains through the opening and forms a small reservoir, called a bleb, on the surface of the eye, which is hidden under the upper eyelid. After having a trabeculectomy, most people’s eye pressures come down enough that eye drops may no longer be needed.
2.Closed angle glaucoma
Acute closed angle glaucoma happens when the eye pressure rises very suddenly, which can cause damage to the optic nerve over a very short space of time. It happens when the outer edge of the iris and cornea come into contact, closing the drainage angle. This stops the aqueous fluid from draining away altogether.
A possible series of mild attacks of misty vision, rainbow-coloured rings around white lights, or achy eyes.
For most people, there’s no warning. A sudden increase in eye pressure is very painful, the eye becomes red and the sight gets worse. There is even a possibility of black outs, feeling nauseous or being sick.
It usually affects only one eye at a time and it’s rare for both eyes to have an attack at the same time.
In case of an acute attack, one would need to go to the hospital immediately to have treatment to lower the eye pressure quickly and prevent permanent sight loss. The treatment is a combination of eye drops and a tablet or injection, which reduces the eye pressure quickly, and eases the pressure and pain. In most cases, if treatment is given quickly, the sight can recover almost completely.
Once the eye pressure is under control again, it’s normal to need some further treatment to prevent from having another attack. Usually, this is a laser treatment to make a small hole in the iris, a procedure known as a peripheral iridotomy.
Occasionally, following all the treatments, eye pressure can remain high. In these cases, regular eye drops might be needed to keep your eye pressure controlled and prevent damage to your optic nerve.
3.Normal tension glaucoma
This type of glaucoma occurs when the eye pressure is within normal range, but causes damage to the optic nerve.
It’s not entirely known why some people’s optic nerve becomes damaged even though their eye pressure is at a normal level. It’s thought that perhaps some people’s optic nerve may just be weaker and unable to cope with an eye pressure within the normal range.
Normal tension glaucoma is treated in the same way as open angle glaucoma – by lowering your eye pressure.
Secondary glaucoma is caused by the effect of another eye condition, an injury to the eye, or certain treatments, medications or operations. The treatment is again aimed at reducing the eye pressure as well as treating the cause.
Congenital glaucoma is a rare form where a baby is born with glaucoma because their drainage system didn’t develop properly before birth. It is usually treated early on in life and is managed by specialist clinics.
Further help and support
The Victoria Eye Unit at The County Hospital in Hereford provides a comprehensive range of ophthalmic services, covering all aspects of general ophthalmology. There is also a dedicated 24/7 Accident and Emergency Ophthalmology service, which is open from 8am till 6pm on working days and from 10am till 4pm on weekends and bank holidays. Other times are staffed by on-call eye doctors and consultants within the main A&E department.
RNIB (Royal National Institute of Blind People
105 Judd Street
London WC1H 9NE
0303 123 9999
International Glaucoma Association (IGA)
15 Highpoint Business Village
Kent TN24 8DH
SightLine (IGA’s helpline)
01233 64 81 70
RNIB,(http://www.rnib.org.uk/eye-health-eye-conditions-z-eye-conditions/glaucoma), 13 March, 2017
Specsavers: https://www.specsavers.co.uk/stores/hereford/families-in-hereford-warned-of-hereditary-link-to-glaucoma, 13 March, 2017
Wye Valley NHS Trust (http://www.wyevalley.nhs.uk/visitors-and-patients/county-hospital-(acute)/a-z-departments/ophthalmology.aspx), 13 March, 2017