Glaucoma is a progressive disease of the eye characterized by degeneration of the optic nerve. The exact pathophysiology is unknown, but increased intraocular pressure is the biggest risk factor. Other risk factors for glaucoma include positive family history, near-sightedness, old age, race (African), and vascular disorders in the eye. The intraocular pressure is a balance between the production of aqueous humor in the ciliary body and the drainage into the canal of Schlemm. Primary glaucoma is categorized into open-angle and closed-angle. Open-angle glaucoma (1) is a chronic disease caused by reduced outflow of the aqueous humor through Schlemm's canal. This results into increased intraocular pressure and damage of the optic nerve resulting in loss of vision. In open-angle glaucoma with normal intraocular pressure, problems with perfusion of the blood vessels cause optic nerve degeneration. Closed-angle
glaucoma (2) is caused by a (congenital) forward ballooning of the peripheral iris so that it touches the back of the cornea, thereby reducing the outflow of the aqueous humor. This situation can be acute or chronic. Reduction of the intraocular pressure is the only proven beneficial therapy for glaucoma. Reduction of the pressure prevents further loss of vision. This reduction can be achieved by reducing the production of aqueous humor with β-antagonists, α-agonists or carbonic anhydrase inhibitors. Another strategy is stimulation of the drainage of the humor with cholinergics or prostaglandin agonists. See the Kompas for more information on drugs in glaucoma.