Glaucoma affects the optic nerve which is found at the back of the eye. The optic nerve sends visual information from the eye to the brain, allowing us to see. In glaucoma, the pressure inside the eyeball is high enough to cause damage to the optic nerve.
Damage starts with peripheral vision.
The speed with which vision deteriorates is usually slow and initially goes unnoticed in the average patient. As the condition progresses, more nerve cells are damaged and the field of vision narrows. If left unchecked, this process can lead to complete blindness. When eye pressure rises, it slowly destroys fibers in the optic nerve. As nerve fibers die, the optic disc gets damaged.