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Glaucoma is a group of eye diseases that cause blindness by damaging the nerve cells located in the back of the eye (the optic nerve). In many cases this damage to the optic nerve is thought to be caused in part by increased pressure in the eye (intraocular pressure, or IOP) that results from the buildup of fluid inside the eye. But damage often occurs without increased IOP.
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In open-angle glaucoma (OAG), the cause of damage to the optic nerve is not well understood. Normally, the shape of the front part of the eye (anterior chamber) is maintained by a fluid called aqueous humor, which is produced in and removed from the eye to maintain a constant pressure. Sometimes the aqueous humor does not drain out of the eye normally, but the reason this occurs is not known. When this happens, fluid builds up inside the eye, causing increased pressure within the eye (IOP). Most people with open-angle glaucoma have higher-than-normal IOP. The increased pressure inside the eye damages the optic nerve, resulting in progressive loss of vision.
But not all people with open-angle glaucoma have increased pressure inside the eye. Estimates vary, but as many as 40% to 50% of people with OAG may occur without increased IOP, and most people with elevated pressures will never get glaucoma.1, 2 The first signs of this type of glaucoma, referred to as normal or low-tension glaucoma, are changes within the eye (enlarged cup-disc ratio) rather than increased pressure in the eye and side (peripheral) vision loss.
See a picture of closed-angle glaucoma.
Congenital and infantile glaucoma
Glaucoma that is present at birth (congenital glaucoma) or that develops in the first few years of life (infantile glaucoma) is often caused by certain birth defects. A birth defect may develop because of an infection in the mother during pregnancy, such as rubella, or because of an inherited condition such as neurofibromatosis.
Glaucoma may also develop as a result of another condition. This is called secondary glaucoma.
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