Glaucoma in Chicago – Center of Excellence:

Glaucoma is a serious, disabling disorder of the optic nerve often related to elevated eye pressure (IOP). It is defined as a pressure related optic neuropathy that causes loss of side vision in the initial and intermediate stages. In later stages, central vision also declines. It can affect persons of all ages, races and genders.

The optic nerve travels from the eye to the brain and carries over 1,000,000 neurons of vision information. If it is damaged the quality of vision suffers. Visual loss is glaucoma has been described as silent and insidious: the sneak thief of sight. It can profoundly affect one's quality of life.

Glaucoma tends to be used as a monolithic term, but in fact there are many varieties.  The two largest headings are open angle glaucoma and narrow angle glaucoma. But within those categories are numerous sub-groups such as pigmentary g. pseudo-exfoliation g. plateau iris, neovascular g., phacomorphic g., juvenile g., and many others.