Glaucoma

Source: all about vision
Glaucoma refers to a group of eye disorders that usually have few or no initial symptoms and eventually cause harm to the optic nerve that carries information from the eye to the brain.
In most cases, glaucoma is associated with higher-than-normal pressure inside the eye (ocular hypertension). If untreated or uncontrolled, glaucoma first causes peripheral vision loss and eventually can lead to blindness.


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http://www.allaboutvision.com/conditions/glaucoma.htm