Glaucoma is an eye condition characterised by loss of vision due to damage of the optic nerve. The optic nerve carries sight images to the brain, and any damage to the nerve results in damage to sight. The eye needs a certain amount of pressure to keep the shape of the eyeball. Usually, but not always, the damage occurs because pressure within the eye increases and presses on the nerve, which damages it. Some people may have an eye pressure within normal limits but damage occurs because there is a weakness in the optic nerve. In most cases both factors are involved but to a varying extent.
There are different types of glaucoma:
- The most common is Chronic (primary open angle) glaucoma – this form usually affects both eyes and develops slowly so that loss of sight is gradual. There is no pain, redness of the eye or dramatic change in vision.
- With Acute (angle closure) glaucoma, there is a sudden increase in the pressure within one eye. The eye becomes red and painful. Often there is mistiness of vision and episodes of seeing haloes around lights.
- Sometimes, other diseases of the eye cause a rise in the pressure within the eye – this group of conditions is called secondary glaucoma.