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 glaucomamay be confused with chronic open-angle glaucoma, another type ofglaucoma.
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.
Angle closure may occur two ways:
- The iris may be pushed forward up against the trabecular meshwork.
- The iris may be pulled up against the trabecular meshwork.
In either case, the position of the iris causes the normally open anterior chamber angle to close. Aqueous humor that should normally drain out of the anterior chamber is trapped inside the eye, thereby increasing the IOP.
Acute Angle-Closure GlaucomaSymptoms
If the ensuing rise in pressure is sudden,pain, blurred vision, and nausea may occur. Optic nerve damage may also occur due to the increased IOP, either in a sudden attack or in intermittent episodes over a long period of time.
Sometimes, the attack may be caused by dilation of the pupils, possibly during an eye examination. In eyes that are anatomically smaller, pupillary block may occur, causing acute angle closure glaucoma. In pupillary block, a brief episode of obstruction of aqueous fluid can occur by the pupil coming into contact with the structures behind it, usually the lens of the eye. This causes the pressure of the fluid behind the iris (in the posterior chamber) to be higher than the pressure of fluid in front of the iris (in the anterior chamber), causing the iris to be pushed forward, initiating closure of the angle.
Acute angle closure glaucoma may be primary or secondary. In primary acute angle closure glaucoma, there is no underlying eye disease that is causing the condition. Secondary acute angle closure glaucoma occurs because of another eye disease or condition, trauma, drugs, or a chronic medical condition.
With acute angle-closure glaucoma, because the rise in pressure is rapid, the symptoms also occur suddenly. Understandably, people who are experiencing acute angle-closure glaucoma are extremely uncomfortable and distressed.
Dramatic symptoms of acute angle-closure glaucoma include the following:
- Severe eye pain
- Nausea and vomiting
- Blurred vision and/or seeing haloes around lights (Haloes and blurred vision occur because the cornea is swollen.)
- Profuse tearing
In acute attacks of angle-closure glaucoma, it is common for only one eye to be involved and for symptoms to worsen over a few hours.
Some people may experience intermittent episodes of angle closure and elevated IOP without ever having a full-blown attack of angle-closure glaucoma. This is called subacute angle-closure glaucoma.
People with subacute angle-closure glaucoma may have no symptoms, or they may experience mild pain, have slightly blurred vision, or see haloes around lights. These symptoms resolve spontaneously as the angle reopens