In angle-closure glaucoma (also "closed-angle glaucoma", "primary angle-closure glaucoma", "acute glaucoma") the iris bows forward and causes physical contact between the iris and trabecular meshwork, which blocks the outflow of aqueous humor from within the eye. This contact may gradually damage the draining function of the meshwork until it fails to keep pace with aqueous production, and the intraocular pressure rises. The onset of symptoms is sudden and causes pain and other symptoms that are noticeable; it is treated as a medical emergency. Unlike open-angle glaucoma, angle-closure glaucoma is a result of the angle between the iris and cornea closing. This tends to occur in the far-sighted, who have smaller-than-normal anterior chambers, making physical contact between the iris and trabecular meshwork more likely. There are a variety of tests to detect people at risk of angle-closure.