When intraocular pressure becomes too high, glaucoma may occur. This occurs because, the eye fluid channel becomes narrow, but the eye fluid (also called aqueous humor) continue to rise.
Open-angle glaucoma (sometimes called wide-angle glaucoma), is the most common glaucoma. This glaucoma type seems to have normal eye structures, but the eye fluid can not smoothly go through the trabecular meshwork.
Angle-closure glaucoma (also called narrow-angle glaucoma), is another type. This glaucoma is less common, but it may cause a sudden eye pressure increase. Because the iris and the cornea form a small angle, eye fluid channel becomes too narrow, causing eye fluid blockage.