Glaucoma is a group of eye diseases that gradually steal sight without warning. In the early stages of the disease, there may be no symptoms. Experts estimate that half of the people affected by glaucoma may 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. There is no cure for glaucoma—yet. 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.

 Optometrists are very aware of the risks for glaucoma and at an eye examination will use special tests to look for the signs of early disease. These tests include measuring the pressure of the eyes (intraocular pressure or IOP), assessing visual fields and examining the apearance of the optic nerve by looking into the eye. Some practices have a speciality in glaucoma testing when the tests are repeated at another time to make sure that the results are consistent.

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