DefinitionGlaucoma refers to a group of eye conditions that lead to damage to the optic nerve, the nerve that carries visual information from the eye to the brain.In many cases, damage to the optic nerve is due to increased pressure in the eye, also known as intraocular pressure (IOP).Alternative NamesOpen-angle glaucoma; Chronic glaucoma; Closed-angle glaucoma; Congenital glaucoma; Angle closure glaucomaCauses, incidence, and risk factorsGlaucoma is the second most common cause of blindness in the United States. There are four major types of glaucoma:Open-angle (chronic) glaucomaAngle-closure (acute) glaucomaCongenital glaucomaSecondary glaucomaThe front part of the eye is filled with a clear fluid called aqueous humor. This fluid is always being made in the back of the eye. It leaves the