What is Acute Angle-Closure Glaucoma?
Acute angle-closure glaucoma is caused by a rapid or sudden increase in intraocular pressure (IOP), the pressure inside the eye.Fluid is continually produced within, and drains out of, the normal eye. This fluid, called aqueous humor, is unrelated to the tears, which are only on the outside of the eye. High pressure inside the eye is caused by an imbalance in the production and drainage of fluid in the eye. If the channels within the eye that normally drain the fluid from inside the eye do not function properly or are blocked, the pressure within the eye will rise. In this case, more fluid is continually being produced but cannot be drained because of the improperly functioning or blocked drainage channels. This results in an increased amount of fluid inside the eye, which is a limited space, thus raising the intraocular pressure.The angle of the eye is the anatomical portion of the eye that contains the structures that allow fluid to drain out of the inside of the eye. The angle is located between the peripheral cornea and the peripheral iris. The angle contains the trabecular meshwork, which acts as a filtration system for the aqueous fluid draining from the eye. In angle-closure glaucoma, the iris (the colored part of the eye) is pushed or pulled up against the trabecular meshwork (or drainage channels) within the angle of the anterior chamber of the eye. When the iris is pushed or pulled up against the trabecular meshwork, the fluid (called aqueous humor) that normally flows out of the eye is blocked and cannot drain out, thereby increasing the IOP. See Multimedia files 1 to 2.If the angle closes suddenly, symptoms are severe and dramatic. Immediate treatment is essential to prevent optic nerve damage and vision loss. If the angle closes intermittently or gradually, angle-closure glaucoma may be confused with chronic open-angle glaucoma, another type of glaucoma.People who have farsightedness (called hyperopia) are at an increased risk for acute angle-closure glaucoma because their eyes are smaller, their anterior chambers are shallower, and their angles are narrower.In the United States, fewer than 10% of glaucoma cases are due to angle-closure glaucoma. In Asia, angle-closure glaucoma is more common than open-angle glaucoma.Certain races (for example, Asians and Eskimos) have narrow angles and, thus, are more likely to develop angle-closure glaucoma than Caucasians. Angle-closure glaucoma among American Indians is lower than among Caucasians.In Caucasians, angle-closure glaucoma is three times higher in women than in men. In African Americans, men and women are affected equally.As people age, the lens of the eye enlarges and pushes the iris forward, thus increasing the risk for angle-closure glaucoma.