Glaucoma is a disease that damages the eye's optic nerve. If you have glaucoma, the aqueous humor does not flow out of the eye properly. Fluid pressure in the eye builds up and, over time, causes damage to the optic nerve fibers. Glaucoma can cause blindness if it is left untreated. Glaucoma is an eye diseases that gradually steals sight without warning. In the early stages of the disease, there may be no symptoms. Many people who have glaucoma do not know they have it. Vision loss is caused by damage to the optic nerve. This nerve acts like an electric cable with over a million wires. It is responsible for carrying images from the eye to the brain. Any vision lost through glaucoma cannot be restored. However, medication or surgery can slow or prevent further vision loss. The appropriate treatment depends upon the type of glaucoma among other factors. Early detection is vital to stopping the progress of the disease. It was once thought that high pressure within the eye, also known as intraocular pressure or IOP, is the main cause of this optic nerve damage. Although IOP is clearly a risk factor, we now know that other factors must also be involved because even people with “normal” levels of pressure can experience vision loss from glaucoma.