Glaucoma is a group of conditions characterised by damage to the optic nerve, as it leaves the back of the eyeball, resulting in defects in the visual field and often associated with raised pressure in the eye (intraocular pressure, or IOP). IOP is the pressure in the eyeball and is related to the balance between production and drainage of aqueous humour (the liquid that fills the front part of the eyeball). The “normal” pressure range is 10 - 21mmHg. However, some patients with IOP within this normal range, may still develop glaucoma, whilst others with IOP well above 21mmHg may never actually develop the condition.
Glaucoma can be characterised according to the shape of the anterior chamber drainage angle, into Open and Closed Angle varieties. In the UK and most Western countries Chronic Open Angle Glaucoma, COAG, (also known as Chronic Simple Glaucoma, CSG) is the type most commonly found in the general population.
Glaucoma affects approx. 2% of the population over the age of 40. You are more likely to be affected if:
- You have a family history of the condition
- You are over 65
- You are very shortsighted
- You have diabetes
- You are of Afro-Caribbean origin
Other risk factors for glaucoma include previous ocular (eye) injury and prolonged use of steroids (eyedrops or tablets).
As well as checking the IOP, your eye surgeon will also need to examine your eyes in general. It is also important to particularly assess the thickness of the central cornea (the front window of the eye), to examine the structures of the anterior chamber drainage angle, to assess pupil reactions, to document changes to the optic nerve head and adjacent nerve fibre layer and also to assess the central and peripheral fields of vision.
Where there is uncertainty that glaucoma may actually be present, the terms Glaucoma Suspect (for those who are pre-glaucomatous and likely to develop glaucoma) or Ocular Hypertensive (for those whose IOP is above 21mmHg but who have no other signs to support the diagnosis of glaucoma) may be used.
Most types of glaucoma are chronic, slowly-progressive conditions where patients are not even aware they have the condition, when it is in the early stages.
It is therefore important to have regular eye checks (once a year) by your optometrist, if you fall in any of the above risk groups. Your optometrist can carry out various tests which may result in early detection of the condition. Treatment can then be commenced, where necessary, earlier than may otherwise have been the case in order to slow down the progression of this condition.
Current treatment strategies are aimed at reducing the intra-ocular pressure (IOP) and thereby reducing the chance of further damage to the optic nerve and subsequent field loss.
There are various strategies for reducing the IOP and these involve either reducing the production of aqueous humour in the eye or increasing its drainage from the eyeball.
- Eyedrops - Most eyedrops work by reducing the rate of production of aqueous humour, e.g. betablockers such as Timolol, carbonic anhydrase inhibitors such as brinzolamide, or alpha agonists such as brimonidine.
Other drops work by increasing the drainage of aqueous humour from the eye, e.g. prostaglandin analogues such as latanoprost.
All eyedrops have possible side effects, some work better in certain individuals than others and some drops should be avoided by certain groups of individuals, e.g. betablockers should be avoided if you have asthma.
- Tablets - The main group of tablets used in glaucoma are carbonic anyhdrase inhibitors such as acetazolamide. These tablets are very effective in reducing the production of aqueous humour. However, they often cause symptoms such as tingling in the hands/feet, or mild GI disturbances. Prolonged use can also affect blood electrolyte levels. As such, drugs such as acetazolamide are often not used on a longterm basis.
- Laser treatments - There are various types of laser treatment which can be used to either increase drainage, or reduce production of the aqueous humour. Laser treatment can be an effective alternative when eyedrops alone are no longer effective in reducing the IOP.
- Surgery - This can be the most effective method in controlling intraocular pressure over the long term. The commonest procedure is known as a trabeculectomy and this involves the creation of a new drainage channel for the aqueous humour. It is often carried out with the aid of anti-scarring agents.
All current treatment strategies for glaucoma are aimed at lowering the IOP. This is the case irrespective of whether the initial IOP was actually above the so-called normal upper limit of 21mmHg, or well within the “normal range”.
Will I go blind?
It can be a worrying time to learn of any new condition diagnosis. However, when newly diagnosed, glaucoma is often at the mildest end of its disease spectrum. The vast majority of those people found to have glaucoma will not go blind but in order to save your vision, it is very important that you adhere to the treatment plan advised by your eye surgeon and that you are followed up regularly.
Can I drive?
Most people with glaucoma are able to drive without any problem. However, if your glaucoma affects both eyes, or if you have glaucoma in one eye and another problem affecting your vision in the fellow eye, then you must inform the DVLA about your eye problems. The DVLA may need you to have further tests but most people are subsequently still able to drive.
Can I prevent glaucoma?
The most common type of glaucoma (COAG/CSG) cannot be prevented. However, if you have a family history of glaucoma then it is important to have regular eye checks by your optician, especially if you are over the age of 40 at which point you may be entitled to free check-ups. This should mean that if glaucoma is present, then it can be diagnosed early and treatment may be commenced before significant optic nerve head damage or visual field loss occur.
Is the condition painful?
The most common type of glaucoma (COAG/CSG) does not usually cause any discomfort. However, some people (e.g. those who are very long-sighted, or who are from the Far East) may be at increased risk of Acute (or chronic) Angle-Closure Glaucoma.