Glaucoma is a disease of the eye caused by increased pressure in the eye which will cause damage to the optic nerve and tunnel vision that progresses to blindness. This increase in pressure is caused by a decrease in the flow of fluid in the eye called aqueous humor. Open-angle glaucoma is a chronic glaucoma and the most common form. It is different from narrow-angle glaucoma which is sudden and a major cause of blindness. Open-angle glaucoma develops gradually and may be suspected if the patient complains of a narrower visual field and a pale papilla is discovered. Several tests will be performed by an ophthalmologist such as a fundus, a measurement of intraocular pressure and a gonioscopy. It is possible to treat glaucoma if it is detected early enough, but unfortunately the first symptoms appear only in advanced stages.