Primary Open-Angle Glaucoma (POAG) is the most common form of glaucoma. The mechanism of its formation is not precisely known, but there is evidently excessive production of intraocular fluid that is not sufficiently drained. The onset and course of primary open-angle glaucoma is slow. It proceeds asymptomatically over a long time frame, and it manifests itself in a sudden deterioration of vision. Impairment that occurs in the optic nerve is, unfortunately, irreversible. For this reason, early detection of the disease is very important. Both eyes are often affected.