- Glaucoma is a leading cause of blindness.
- Glaucoma rarely affects people under the age of forty.
- In the UK it affects 2% of people over the age of forty.
- There is an estimated 250,000 people in the UK with the condition and it is estimated that only half of the people with glaucoma have been detected.
- Blindness is preventable if glaucoma is diagnosed and treated early enough.
- Glaucoma is not catching and is not caused by diet, work or any other factors.
- Glaucoma can be controlled with treatment but not cured.
- Glaucoma cannot be prevented but having regular eye checks will enable early diagnosis and treatment and this applies particularly to the above categories. In the UK sight tests are free for people with diabetes and for close relatives of people with glaucoma once they are over 40 years old.
What is glaucoma?
Glaucoma is a condition where there is loss of vision due to damage to the optic nerve that carries the images from the retina to the brain. Usually glaucoma is accompanied by an increased pressure in the eye, but not always. This pressure is called the intra-ocular pressure or IOP. It is this pressure that damages the optic nerve.
There are different types of glaucoma:
Chronic open angle glaucoma – this is the most common form of glaucoma. It produces no symptoms – no pain or redness of the eye and the eyesight seems unchanged. It usually affects both eyes and develops slowly so the loss of sight is gradual.
The whole of the contents of the eyeball are nourished by a fluid, called the aqueous humour. This fluid circulates within the eyeball and leaves the eye by small drainage tubes at the front. If there is an obstruction within this system, then the fluid cannot escape and pressure builds up within the eye. It is this persistent increased pressure that may damage the optic nerve and cause vision loss.
Those most at risk of developing open angle glaucoma are:
- People of Afro-Caribbean origin are between 5 and 8 times more likely to have glaucoma and it may come on earlier and be more severe.
- People with a family history of glaucoma are more at risk. There is a 6 times greater risk if a near relative has it.
- People who are very short sighted [myopic] are more at risk.
Acute angle glaucoma – Is where there is a sudden increase in the pressure [IOP] in one eye. The eye becomes red and painful often accompanied by misty vision and seeing haloes around lights.
Secondary glaucoma – This is a group of conditions where the IOP is raised and this is caused by other diseases of the eye.
Congenital glaucoma -Is where glaucoma is present at birth.
Note: it has been thought that people with diabetes are more susceptible to glaucoma. However, recent research suggests that the higher incidence of glaucoma in people with diabetes is more likely to be due to s greater detection rate because people with diabetes often have more frequent regular eye checks than the general population.
Tests for glaucoma
At a high street optometrist – there are 3 tests that should be done to but not all optometrists do all three tests, so check when you make your appointment.
The 3 tests are:
- To look at the back of the eye and the optic nerve with a bright light [ophthalmoscope]
- Measurement of the pressure [often called the puffer test]. A raised pressure at this stage does not necessarily mean you have glaucoma.
- Field of vision test where you are asked to look at a screen with a series of spots of light and you will be asked which ones you can see.
If there are any abnormalities then the optometrist will refer you to your GP for referral to the hospital.
At the hospital – the following tests will take place at your hospital visit:
Measurement of the intra-ocular pressure – The eye is numbed by a drop of anaesthetic and the eye observed through an instrument called a slit lamp. The cornea [the front of the eye] is lightly touched with an instrument that measures the pressure.
One or more of the following tests will also be carried out:
Gonioscopy – This allows the doctor to observe the angle between the iris and the cornea.
Visual field measurement – You sit at a screen and keep your gaze fixed on a central light. Other lights flash on and off and you press a button when you see them. This test detects any blind areas of your visual field indicating where the nerve damage has occurred.
Optic nerve assessment – Drops are put in the eye to dilate the pupil so that the doctor can examine the back of the eye more fully and to record the health of the optic nerve by the appearance of the optic disk. Retinal photographs may also be taken so that these can be kept in your records to establish any changes in the future.
Note: You should NEVER drive yourself to the hospital because the drops used to dilate your pupils leave the vision blurry for a few hours.
Eyedrops – The aim of treatment is to lower the intra-ocular pressure and prevent further vision loss. Most people with glaucoma require life-long treatment, usually with eye drops.
Surgery – In some cases the intra-ocular pressure can be reduced by opening up the draining channels with laser treatment or by surgery to make a small drainage hole at the top of the eyeball. In these cases, the need for ongoing treatment may be removed but not all cases are suitable and the majority of people with glaucoma need eye drops for the rest of their lives.
Tablets – In some cases tablets may be given to reduce the amount of aqueous produced. Initially these tablets increase the amount of urine passed.
Glaucoma and exercise – The Medical Director of the Glaucoma Foundation in the US says that there is research that shows that frequent activity such as swimming or brisk walking can lower the pressure within the eye. But he warns against sports that involve turning upside down – certain yoga positions and scuba diving, may raise the pressure. [Reported in Health Which? December 2000]
Glaucoma and driving – If glaucoma is diagnosed then you should inform the DVLA and your motor insurers. It is a condition that should be declared under the item ‘has there been any material change that could affect your driving.’ If you were involved in an accident and you had not declared that you have glaucoma, then you may not be insured and the DVLA could take action because you have not informed them.
More Information about glaucoma can be obtained from:
International Glaucoma Association
15 Highpoint Business Village
Sightline (helpline) number: 01233 648 170
Administration number: 01233 648 164