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Glaucoma is the name for a group of diseases affecting the eyes, in which the optic nerve becomes damaged. The cause of the damage is often raised pressure within the eye. The most common type of glaucoma, called open angle glaucoma (also called chronic glaucoma or chronic simple glaucoma), affects 1 in 100 people over the age of 40, and becomes more common with increasing age. Glaucoma can lead to blindness, but if it’s detected and treated early, this can usually be prevented.
The eyeball is filled with a fluid, which creates a pressure inside the eye that keeps the shape of the eyeball and enables the eye to work properly.
The watery fluid in the front part of the eye (aqueous humour) is produced in the eye, near the iris. It drains back into the bloodstream through sieve-like channels (called the trabecular meshwork). Normally, the amount of fluid produced is balanced by the amount draining away, so that the pressure in the eye stays constant.
In most people with glaucoma, an increase in the pressure inside the eye causes optic nerve damage. This usually happens because the fluid cannot drain away properly.
However, the cause of glaucoma is not completely understood. Some people have high internal eye pressure but do not develop optic nerve damage, while in others the nerve becomes damaged despite normal internal eye pressure.
Other factors, such as poor blood supply to the optic nerve or a weakness in the nerve, may also be involved.
There are two main types of glaucoma: open angle glaucoma and closed angle glaucoma. In open angle glaucoma, the drainage channels become blocked over several years resulting in a gradual increase in pressure and worsening of vision.
Closed angle glaucoma (also called acute glaucoma) is much less common. It involves a sudden, complete blockage of the drainage channels and can result in permanent blindness if not treated promptly. Symptoms usually affect only one eye. The eye becomes red and extremely painful, and this may be accompanied by a headache, vomiting and blurred vision. Closed angle glaucoma needs immediate treatment in hospital. This usually involves medicines to reduce the pressure in the eye followed by laser treatment or surgery. The other eye is usually also treated, because there is a strong chance it will develop the same problem. If treated quickly there can be almost complete and permanent recovery of vision.
There are two other uncommon types of glaucoma: secondary glaucoma, in which the rise in internal eye pressure is the result of another eye condition, and congenital glaucoma due to a physical abnormality of the eye present at birth.
In open angle glaucoma, pressure inside the eye builds up slowly and painlessly. As the optic nerve is gradually damaged the field of vision is reduced, so that eventually only a small area of central vision remains - “tunnel vision” - before sight is lost completely. Most people do not have any symptoms until they notice some loss of vision.
Screening tests are needed to detect glaucoma before there is significant loss of vision. Ideally, all people over 40 should have their eyes checked for glaucoma by an ophthalmologist every two years. It is especially important for those who have a family history of glaucoma.
There are three simple and painless tests that an optometrist can do:
- Ophthalmoscopy – this is when the optometrist looks at the back of the eye with a special instrument (ophthalmoscope). Damage to the optic nerve can be seen at the back of the eye,
- Tonometry - this is when the measures the internal pressure of the eye. This is done by using a device that blows a small puff of air onto the eyeball
- Field of vision test – this is done by showing a sequence of spots of lights and asking which can be seen.
Treatments for glaucoma aim to lower the internal pressure of the eye and prevent any loss of vision, or any further deterioration in vision. Treatments include medicines given as eye drops, laser treatment and surgery. Treatment cannot reverse any existing optic nerve damage, so it won’t improve sight if it has already deteriorated.
There are several different types of medicine available as eye drops for treating open angle glaucoma. They help lower the internal pressure of the eye either by increasing the flow of fluid out through the drainage channels or by reducing production of fluid. A beta-blocker (such as betaxolol) is often tried first. Beta-blocker eye drops must not be used by people who have asthma, a slow heart beat, heart block or heart failure, because the medicine can be absorbed into the bloodstream and cause serious problems in people with these conditions.
Several other types of drugs in drops and tablet form are available as alternatives or in addition to beta-blockers.
It is important that any prescribed eye drops are used every day, or the pressure in the eye will rise again. There are combination eye drops available that might be more convenient for people who need to use two different medicines.
Side effects: All the eye drop medicines can cause some irritation to the eyes. In addition, beta-blockers can cause itching and dry eyes. Side effects of the other drugs might include taste disturbance, bitter taste, darkening of the iris and thickening and lengthening of eye lashes, headache and blurred vision.
A laser can be used to open the holes in the trabecular meshwork. The procedure is usually quick and causes little discomfort. No general anaesthetic is required and there is no need for an overnight stay in hospital. The success of this type of treatment varies from person to person, and it may be necessary to continue using eye drops after laser treatment, though often at a lower dose.
Surgery is used when medicines and/or laser treatment has failed to lower pressure in the eye enough. Surgery is increasingly used sooner rather than later in people with glaucoma who are young, or who have particularly high internal eye pressure. The operation is straightforward and involves creating a tiny opening in the eye wall, which allows fluid to escape into the loose tissue under the conjunctiva (the clear membrane that covers the white of the eye). From there it is absorbed back into the bloodstream. The operation often makes further treatment with eye drops or tablets unnecessary, but about 1 in 5 people need to keep using medicines.
1. Does it help to follow a particular diet?
No, there's no evidence that following a particular diet helps to treat or prevent glaucoma.
Many claims have been made about following different diets and taking various supplements to treat glaucoma. However, there is little, if any, scientific evidence to back up these claims. Aim to eat a balanced diet that's low in saturated fat, sugar and salt and high in fibre, vegetables and fruit.
It's best not to drink large volumes of fluid in a short period of time, as this can temporarily raise pressure in your eye.
2. What if I forget to put in my eye drops?
If you forget a dose, put in your eye drops as soon as you remember.
It isn't a problem if you forget to use your eye drops on the odd occasion. However, it's important to get into a routine of using your eye drops at around the same time every day to help you remember.
Try using a chart with tick boxes to keep a check on whether you have taken your eye drops every day. You could also set a timer to ring at a particular time to remind you when you need to put them in.
Using your drops regularly, as advised by your doctor, offers the best protection against glaucoma and will prevent it getting worse.
- American Academy of Ophthalmology (AAO)
- The International Glaucoma Association (IGA)
- The Royal National Institute for the Blind (RNIB)
- The Royal College of Ophthalmologists (RCO)
- International Glaucoma Association
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