What is Glaucoma?
Glaucoma is the name given to a group of eye conditions that result in damage to the optic nerve. The optic nerve is found at the back of the eye and takes the signals for sight from the eye to the brain. Glaucoma is a common cause of blindness worldwide but can be treated to prevent blindness in most patients if detected early. Unfortunately, any sight lost from glaucoma can not be recovered.
For the vast majority of patients, glaucoma is a very slow disease and causes no symptoms until very late on when significant damage to the vision has occurred. This is because, vision lost may be in the periphery and no blurring occurs early on. For this reason, glaucoma is known as ‘the sneak thief of sight’. It is therefore important to detect glaucoma early because most patients treated for glaucoma do not lose vision.
Who can get glaucoma?
Glaucoma can occur at any age, but is rare in children and young adults. It becomes increasingly common with age and is thought to affect 2 in every 100 people over the age of 40. This rises to 1 in every 10 patients over the age of 75. As well as old age, other groups of people that are at increased risk include relatives of patients already with glaucoma, people with high pressure in their eyes, people of African descent, diabetic patients and short-sighted patients.
How do I know if I may have glaucoma?
Most patients with glaucoma are detected by the optometrist following a routine sight test at the opticians. Tests to detect glaucoma include:
measuring the pressure in the eye (intraocular pressure)
examining the optic nerve
a test of vision using spots of light to detect any damage (visual field test)
If the optometrist suspects glaucoma, patients are referred to the eye department for further investigations and treatment if appropriate. It is possible to have glaucoma even with a normal eye pressure, because the optic nerve in some people is particularly vulnerable; conversely, not everybody with a high eye pressure develops glaucoma as some people have very resilient optic nerves.
Following assessment in the eye clinic you may be diagnosed as one of the following:
Normal examination: No evidence for glaucoma is found i.e. normal optic nerves, visual fields and eye pressure. Patients are reassured that there is no evidence of glaucoma and discharged. You should still continue with regular eye checks at the opticians.
Glaucoma: There is visible damage to the optic nerve and evidence of loss of vision on the visual field test, with or without raised eye pressure. Patients will require life-long treatment and regular monitoring to prevent further damage to vision.
Ocular Hypertension: Consistently raised eye pressure (greater than 21mmHg) but no evidence of damage to the optic nerve and normal visual field. Patients may or may not require treatment depending on future risk of glaucoma, but all require regular monitoring to detect glaucoma early, if it develops. This may be in the hospital or by your local optometrist.
Glaucoma suspect: Regardless of the level of eye pressure, the optic nerve and/or visual field test suggest glaucoma damage. Some patients require treatment and all require regular monitoring until more definite evidence for glaucoma is available. After monitoring for a few years, if definite evidence for glaucoma is not apparent, some patients can be discharged.
Treatment is aimed at preventing damage to the optic nerve. In doing so, the vision is preserved and blindness prevented. Of all the risk factors for glaucoma (old age, ethnicity, family history and eye pressure), the only treatable one is eye pressure. The main treatment for glaucoma therefore is to reduce pressure in the eye. Treatment is usually for life and regular check-ups are required to ensure treatment is working.
The commonest form of treatment is with eye drops to lower the pressure. They work by reducing the amount of fluid produced in the eye or by increasing drainage of fluid from the eye. If eye drops do not reduce the pressure sufficiently, the specialist may advise either laser treatment or an operation to improve drainage of fluid from the eye. Your specialist will discuss the risks and benefits of treatment with you and advise which is best in your particular case.
Frequently asked questions
Will I go blind?
The majority of patients treated for glaucoma do not go blind. It is however important that patients use their eye drops as advised on a daily basis to ensure that the treatment to prevent blindness continues to work.
Why does pressure build up in the eye?
Within the eye, fluid (called aqueous humour) is continuously produced that both nourishes the inside of the eye and gives the eye its shape. This fluid is also continuously leaving the eye through a natural drain called the trabecular meshwork. When the drain becomes closed or clogged up, the fluid finds it increasingly difficult to exit the eye and pressure builds up within the eye. The upper limit of normal eye pressure is 21 mm Hg.
Does everybody with raised eye pressure develop glaucoma?
No. The latest research shows that nearly 90% of patients with high pressure in the eye do not develop glaucoma, even without treatment, over a 5 year period. People with high pressure but healthy optic nerves and visual fields, i.e. no glaucoma, are said to have ocular hypertension.
Does everybody with ocular hypertension need treatment?
No. We treat those patients that are particularly at risk of developing glaucoma. The risk of developing glaucoma is higher with increasing age and is also higher, the higher the eye pressure. Other tests the doctor will consider include central corneal thickness (a measure of the thickness of the clear window at the front of the eye), the appearance of the optic nerve and the result of the visual field test. Based on an individual risk assessment, the specialist may advise treatment to lower eye pressure if there is significant risk of glaucoma developing over your lifetime.
Why do I need treatment to lower eye pressure if it is already normal?
Approximately 30% of people with glaucoma in the U.K have a normal eye pressure before treatment. It is thought that these patients have particularly vulnerable optic nerves that are susceptible to damage even at normal pressure. This is called normal pressure or low pressure glaucoma. There is evidence though that reducing the pressure to an even lower level in these patients, helps prevent further sight loss.
Does glaucoma run in families?
Having a close relative with glaucoma does increase your chance of glaucoma. Family members should be advised to have regular eye tests, especially if aged over 40. People over the age of 40 with an immediate family member diagnosed with glaucoma – parents, children or siblings – are entitled to a sight test every year under the NHS, without charge.
Can glaucoma be cured?
No. Damage already done can not be repaired. With early diagnosis and regular treatment however, any further damage to sight can be prevented and vision preserved indefinitely.
Do I need to continue drops for life?
As mentioned above, glaucoma can not be cured only controlled by lowering the eye pressure. If drops are prescribed to lower eye pressure, then treatment is usually for life. Patients must make sure a repeat prescription is issued by their family doctor on a regular basis and continue with drops unless instructed otherwise by their specialist.
Can I still drive if I have glaucoma?
Most patients with mild glaucoma are able to continue driving. However, you have a duty to inform the DVLA if you are diagnosed with glaucoma in both eyes. The DVLA have the final say in whether it is safe and legal for you to continue driving.
You may also want to inform your insurance company.
Is there anything else I can do to help my eye pressure / glaucoma?
At present the only proven treatment for glaucoma is eye pressure lowering. By ensuring regular use of drops and attending for regular review you will help prevent sight loss.
Where can I get more information?
Your hospital eye specialist will be happy to help with any specific queries. More information about glaucoma can be obtained from:
Royal National Institute of Blind People
105 Judd Street, London
Tel: 0845 766 9999
Royal College of Ophthalmologists
17 Cornwall Terrace, London
Tel: 020 7935 0702
The International Glaucoma association (IGA)
Woodcote House, 15 Highpoint Business Village
Henwood, Ashford, Kent
Sightline: 01233 648170
Driver and Vehicle Licensing Agency (DVLA)
Drivers Medical Group
Driver Customer Services (DCS)
Correspondence team DVLA
Swansea SA6 7JL
Tel: 0870 240 0009