This disease happens because of increased pressure in the eye. The pressure causes damage to the optic nerve. This can cause loss of vision, and may also be painful.
Sometimes, it is hard for a person to know that they have glaucoma. The vision can be lost very slowly. When sight is lost from glaucoma, it cannot be recovered.
There are two kinds of glaucoma, the kind that happens very fast, and the kind that happens slowly, over a long time.
Glaucoma is the second most common cause of blindness in the world.
There is often a hereditary tendency to glaucoma. A family history of glaucoma is a risk factor. The relative risk of having what is called "primary open-angle glaucoma" (POAG) is increased about two- to four-fold for people who have a sibling with glaucoma. Glaucoma, particularly primary open-angle glaucoma, is associated with mutations in several different genes
Also, the likelihood of it happening is different in different populations. Glaucoma is the leading cause of blindness in African Americans, who have higher rates of primary open angle glaucoma.
- Myron Yanoff & Jay S. Duker 2009. Ophthalmology. 3rd ed, Mosby Elsevier, p. 1096. ISBN 9780323043328
- Wang N, Wu H, Fan Z. 2002. Primary angle closure glaucoma in Chinese and Western populations. Chin Med J. 115 (11): 1706–15. 
- Sommer, Alfred et al 1991. Racial differences in the cause-specific prevalence of blindness in East Baltimore. New England Journal of Medicine 325 (20) 1412–1417.