This is a raising of the intraocular pressure (IOP) associated to a suffering of the optic nerve which progressively loses its function.

The disease has usually a higher incidence after 40 years of age and has often a familial correlation. In the majority of cases the patient is asymptomatic until the visual field defect becomes great, and thus it is very important to preventively regularly measure the intraocular pressure after 40 years of age, especially in patients at risk.