In the most common form of glaucoma, increased eye pressure leads to optic nerve damage and loss of vision. The eye is filled with circulating fluid that nourishes its internal structures. Sometimes the balance between fluid creation and exit is abnormal. The buildup of fluid increases pressure and damages the optic nerve at the back — the bundle of 1 million nerve fibers that carry information to the brain. Without treatment, glaucoma can cause total blindness.
The bright yellow circle shows an optic nerve head that is damaged by glaucoma. The dark central area is the macula, responsible for finely-detailed central vision.