I'm Stephen Vernon, Consultant Ophthalmologist

at University Hospital, Nottingham,

specialising in glaucoma and diabetic retinopathy.

There are lots of different types of glaucoma,

but the commonest one in the UK

is chronic simple or chronic open-angle glaucoma.

This is a condition that gets progressively more common

as one gets older.

The prevalence of the disease,

that means the number of people in the population with the disease,

is about two per cent over the age of 40,

but that rises to about five to six per cent over the age of 75.

People from African origin

are much more likely to have glaucoma than people from European origin,

and if you have a family member with glaucoma,

particularly a brother or sister,

then you again are much more likely to have glaucoma.

In fact, your lifetime risk is about 20 per cent.

The big problem with chronic glaucoma is in its diagnosis

because there are no symptoms to this condition until it is really advanced.

What happens in most people

is that the pressure in the eye is above the pressure that it should be

and over a period of time that damages the nerve at the back of the eye.

And when the nerve is damaged you then get damage to the side vision,

to the peripheral visual field.

To begin with, you don't notice this

because it's rather like having blank patches in your vision.

They're not black patches, they're blank patches

and your brain fills in the gaps.

It's often different in the two eyes

and you can have blank patches in different positions in the two eyes

so that with both eyes open everything seems OK.

But gradually these blank patches will enlarge

and they will progress towards your central vision

and in the later stages of the disease that central vision can be affected.

There are a number of ways in which we diagnose glaucoma.

We can measure the intraocular pressure

and if that is raised then one is certainly a glaucoma suspect

and may have the disease.

One can look at the back of the eye, at the optic nerve head,

to see if there are any specific changes of glaucoma,

and one can perform visual field tests.

We now know that you need to lose about 30 per cent of the function of your eye

before the visual field test will pick up any abnormality at all,

and in most of those patients

an abnormality can be seen at the back of the eye,

either at the optic nerve head or in the retinal nerve fibre layer,

using special instrumentation.

The mainstay of glaucoma treatment in the UK is eye drop therapy.

It's important that a patient who is advised to use their eye drops

continues to use them until the doctor says otherwise,

because it's not just a short course of drops,

this is a course of drops ad infinitum

and sometimes for the rest of the patient's life

to prevent them losing significant vision from the disease process.

An alternative to eye drop treatment is laser treatment.

It is carried out as a day-case patient

and is usually completely painless and takes about two minutes to perform.

If there is evidence that the glaucoma is progressing

and treatment with eye drops and perhaps laser

has failed to lower the pressure sufficiently,

then we may need to go on to an operation.

There are a number of different designs of operation

which all aim to do the same thing,

and that's to release the fluid from inside the eye to outside the eye

by creating an artificial passageway

through the sclera, that's the white of the eye.

The success rate of the operation is measured

by how long it keeps the intraocular pressure at a level that you want.

Unfortunately, over a period of time, the operation may become less efficient

and sometimes patients need to go back on eye drops

or perhaps have a repeat operation.

Fortunately it is very rare to lose your vision completely from glaucoma,

providing you present at an early stage.

So it's really important to make sure that you go to your optician

and get tested for glaucoma

if you're in a high-risk group or even if you're over the age of 40.