Causes

Chronic open-angle glaucoma (primary open-angle) is the most common form of glaucoma, accounting for 90% of all glaucoma cases. It is caused by an overproduction of aqueous humor or obstruction to its flow through the trabecular meshwork or the canal of Schlemm. The chamber angles between the iris and the cornea remain open. IOP intensifies gradually because aqueous humor cannot leave the eye at the same rate that it is produced.

Acute glaucoma, also referred to as closed-angle glaucoma or narrow-angle glaucoma, is less common and, with its sudden onset, is treated as an emergency situation. Obstruction of the outflow of aqueous humor occurs by anterior displacement of the iris against the cornea, which narrows or obstructs the chamber angle. Attacks of acute glaucoma are caused by injury, pupil dilation, or stress. Secondary glaucoma occurs in other diseases of the eye when the circulation of

372 Glaucoma aqueous humor is disrupted with either a decreased angle or an increased intraocular volume. Uveitis, iritis, trauma, tumors, and postsurgical procedures on the eye are common causes of secondary glaucoma. Congenital glaucoma is caused by an autosomal recessive trait that results in dysfunctional development of the trabecular meshwork through which aqueous humor flows.

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