OPHTHALMIC EDUCATION (3) Understanding GLAUCOMA [Archives:2000/22/Health]

By Mahfouth A. Bamashmus FRCSEd, FRCOphth
Consultant Ophthalmic Surgeon
Ibn-Al-Haitham Clinic
University of Science & Technology, Sana’a
What is Glaucoma?
Glaucoma is the name for a group of eye conditions in which the optic nerve is damaged at the point where it leaves the eye. The optic nerve carries information from the light sensitive layer in our eye, the retina, to the brain where it is perceived as a picture.
Our eye needs a certain amount of pressure to keep the eyeball in shape so that it can work properly. When the eye pressure is raised it damages the optic nerve as it exits the eye. Remember that eye pressure is largely independent of blood pressure.
What controls pressure in the eye?
A layer of cells behind the iris (the colored part of the eye) produces a watery fluid, called aqueous. The fluid passes through a hole in the centre of the iris (called the pupil) to leave the eye through tiny drainage channels.
Normally the fluid produced is balanced by the fluid draining out, but if it cannot escape, or too much is produced, then our eye pressure will rise. (The aqueous fluid has nothing to do with tears).
Why can increased eye pressure be serious?
If the optic nerve comes under too much pressure then it can be injured. How much damage there is will depend on how much pressure there is and how long it has lasted. A really high pressure will damage the optic nerve immediately.
Are there different types of glaucoma?
Yes, there are four main types: –
1. Chronic Glaucoma Ð this is the commonest type. The eye pressure rises very slowly and there is no pain to show there is a problem, but the field of vision gradually becomes impaired.
2. Acute Glaucoma Ð is less common. This happens when there is a sudden and more complete blockage to the flow of aqueous fluid to the eye. This can be quite painful and will cause permanent damage to your sight if not treated promptly.
3. Secondary Glaucoma Ð due to previous eye diseases.
4. Congenital Glaucoma (Buphthalmos) Ð is a rare form of glaucoma that affects babies and young children.
How common is Glaucoma?
There is no statistics relating to incidence of Glaucoma in Yemen, but about 2 in 100 people over the age of 40 may have some form of glaucoma.
Are some people particularly at risk of chronic glaucoma?
Yes. There are several factors which increase the risk: –
1. Age Ð chronic glaucoma becomes much more common with increasing age. It is uncommon below the age of 40.
2. Race Ð if you are of African origin you are more at risk of chronic glaucoma and it may come on somewhat earlier and be more severe.
3. Family Ð if you have a close relative who has chronic glaucoma then you should have eye tests at intervals. You should advise other members of your family to do the same. This is especially important if you are over 40 years old when tests should be done every two years.
4. Short sight Ð people with a severer short sight are more prone to chronic glaucoma.
5. Diabetes Ð it is believed to increase the risk of developing glaucoma.
Why can chronic glaucoma be a serious risk to sight?
The danger with chronic glaucoma is that your eye may seem perfectly normal. There is no pain and your eyesight will seem to be unchanged, but your vision may be damaged. The loss of visual field is gradual and it leads to tunnel vision and blindness.
How can chronic glaucoma be detected?
As glaucoma becomes much more common over the age of forty you should have regular eye tests at least every two years. The eye doctor will look for the following:
1. Viewing your optic nerve.
2. Measuring the pressure in the eye using a special instrument.
3. Examining your visual field if the above two are abnormal.
How is chronic glaucoma treated?
The main treatment for chronic glaucoma aims to reduce the pressure in your eyes. Treatment has to start immediately (many people think that they have to wait until they completely loose their sight before starting treatment, because they confuse between cataract and glaucoma). Treatment is usually with drops or in certain cases an operation to reduce the eye pressure. The main aim of treatment is to preserve what is left of sight and visual field and not to cure what has been lost (any damage caused by glaucoma is irreversible).
REMEMBER:
– The earlier the disease is diagnosed the better the results of treatment, because it is extremely difficult to treat advanced cases.
– Any of optic nerve fiber that are damaged by glaucoma cannot be restored and the aim of the treatment is to preserve what is left of optic nerve fibers.
– If you have a relative with glaucoma, you need to visit your eye doctor for a check-up.
Routine eye exam by an eye specialist is very important. It is your sight and your eyes need every care they deserve.
Reference: Royal College of Ophthalmologists educational leaflets, London.

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