What are the different types of glaucoma?

Glaucoma is an eye condition in which vision is lost because of damage to the optic nerve. There are two main types. The most common form of glaucoma is called primary open angle glaucoma, fluid circulates freely in the eye and the pressure tends to rise slowly over time. A less common form of the disease, called acute or angle closure glaucoma, develops suddenly and usually causes eye pain and redness. In this form of glaucoma, pressures rise quickly because normal fluid flow within the eye becomes blocked.