Glaucoma

Q. What is glaucoma?
A. Glaucoma is a condition in which the nerve cells which transmit information from the eye to the brain become damaged. This prevents visual information from getting from the retina in the eye to the brain. Glaucoma is often associated with a build-up of pressure in the eye. The eye is normally filled with fluid which is constantly being replaced. If excessive amounts of fluid are produced, or if it cannot drain away properly, the pressure inside the eye can increase. In some forms of glaucoma, the pressure inside the eye can become extremely high, while in other forms the pressure may remain normal.

The normal appearance of the optic nerve head is shown above. Note that there is a small central circular area called the physiological cup. In the normal eye this circular area is about 1/3 the diameter of the entire optic nerve head. It is this area that is affected in glaucoma.

In the advanced stages of glaucoma the 'cup' has enlarged considerably. This indicates that damage has occurred to the many individual nerve fibres (approximately 1,000,000) which make up the larger optic nerve. Each of these nerve fibres is responsible for part of your visual field.

Q. What causes glaucoma?
A. The exact causes of glaucoma are not known. In some cases the drainage network of the eye may not be formed properly, or may become blocked by natural materials or due to injury; in other cases there is no clear cause.

Q. Is the damage that occurs in glaucoma serious?
A. If untreated, glaucoma can cause blindness. As the nerve cells are progressively damaged, the ability to see objects in different parts of the visual field is lost. This can progress until only central vision is left or until the person is completely blind. The longer the disease is left untreated, the greater is the likelihood of damage. Once damage has occurred it cannot be reversed, although often it is possible to prevent further damage. Modern examination techniques and treatment have made glaucoma a rare cause of blindness in Australia.

Q. How can I tell if I have glaucoma?
A. Often you will not be aware that you have glaucoma until it is too late. Usually there are no symptoms until permanent damage has occurred. In some cases the increased pressure in the eye will cause blurred vision, apparent coloured rings around lights, loss of side vision, and pain and redness of the eye.

Q. How does an optometrist diagnose glaucoma?
A. To diagnose glaucoma the optometrist looks at the nerve fibres at the back of the eye, examines the eye's drainage network, measures the pressure in the eye with a special instrument called a tonometer and sometimes tests the field of vision. These tests are simple and painless.