Glaucoma causes damage to the optic nerve and results in a loss of visual field. The visual field is the whole area that can be seen from side to side and top to bottom when looking straight ahead. "Tunnel vision" is the term usually used to describe the visual field that results from glaucoma.

An increase in eye pressure is usually associated with the disease but glaucoma can also be present when the pressure is normal. It is also possible to have high intraocular pressure without having glaucoma.

The factors which increase the chances of getting glaucoma include: family history of the disease, aging, diabetes and high myopia.

Intraocular pressure is the pressure of the fluid within the eye that allows the "eyeball" to keep its shape. Fresh fluid is always being produced and old fluid must be drained from the eye between the lens and the iris. If the drainage is hampered, high pressure will result. This pressure will wear on the optic nerve which transmits visual information to the brain.

Treatments for glaucoma include: eye drops, pills, laser treatment and surgery.

Symptoms of glaucoma include: pain around the eye, redness of the eye, blurred vision with colored haloes, severe headaches, nausea and vomiting.

Although it is unusual, children can have glaucoma too.

Diet and lifestyle have very little influence on intraocular pressure.

There is no cure for chronic glaucoma. Treatment consists in controlling the progress of the disease and preventing further damage.

The doctor to see if you want to have your eyes checked for glaucoma is an ophthalmologist.