Glaucoma is a complicated disease, or group of diseases, in which changes occur to the optic nerve in the area where it enters the back of the eye, in the area of the retina known at the optic disc. An excavated area of the disc, known as the optic cup, becomes enlarged, destroying nerve fibers in the retina. It is thought that this is due to increased pressure in the anterior portion of the eye. Indeed, treatment plans for glaucoma involve medication or surgeries, which enhance the outflow of fluid from the anterior chamber of the eye in an attempt to lower intraocular pressure. The most common type of glaucoma is primary open angle glaucoma, which may have no symptoms in its early stages.
It is detected by several tests done in a routine comprehensive eye exam, including ophthalmoscopy or inspection of the eye interior (in which the eye doctor can view the retina and see images such as those shown here, where a normal cup has later developed into a pathological glaucomatous cup), tonometry, which measures intraocular tension or pressure, and visual field studies, often using an instrument known as an autoperiemeter, which illustrate the peripheral vision which is the first vision lost in glaucoma.
This link provided by the National Institute of Health discusses the mechanisms involved in the development and treatments for the glaucoma Recent news articles about glaucoma compiled by AllAboutVision.com are available at this link: http://www.allaboutvision.com/conditions/glaucoma_news.htm