Narrow-Angle Glaucoma

Acute narrow-angle glaucoma occurs suddenly, when the colored portion of your eye (iris) is pushed or pulled forward. This causes blockage of the filtration angle of the eye, where the trabecular meshwork allows outflow of fluids.

When internal eye structures are blocked in this way, your eye's internal pressure (intraocular pressure) may spike and possibly damage the optic nerve that transmits images from the eye to the brain.

Acute angle-closure (closed-angle or narrow angle) glaucoma produces symptoms such as eye pain, headaches, halos around lights, dilated pupils, vision loss, red eyes, nausea and vomiting.

These signs may last for hours or until the IOP is reduced. With each narrow angle glaucoma attack, part of your peripheral field of vision may be lost.

Acute angle-closure glaucoma is a medical emergency. If the high pressure is not reduced within hours, it can damage vision permanently. Anyone who experiences these symptoms should contact an ophthalmologist immediately or go to a hospital emergency room.

Some chronic forms of narrow-angle glaucoma, however, can progress very slowly to cause eye damage without any obvious symptoms or pain in early stages.

Causes of the abnormal positioning of the iris in narrow-angle glaucoma include:

• Pupillary block. Eye fluids known as the aqueous humor are produced in the ciliary body, which is located behind the iris. Normally, the aqueous flows easily through the pupil into the front or anterior chamber of the eye. But if the back of the iris adheres to the lens inside the eye, this pupillary channel becomes blocked. Then fluid backs up behind the iris, pushing the iris forward until it closes the drainage angle in the anterior chamber.
   
• Iris plateau. In this condition, the iris is attached to the ciliary body too close to the trabecular meshwork, where drainage occurs. When the pupil dilates, the peripheral iris tissue bunches up in the filtration angle and can cover up the drainage meshwork, causing IOP to rise quickly. This type of narrow-angle glaucoma attack can occur in conditions when the pupil dilates in dim lighting or when eye drops are used to intentionally enlarge the pupil during an eye exam.
   
• Hyperopia. People who are farsighted are more likely to have shallow anterior chambers and narrow angles, increasing their risk for angle-closure glaucoma from pupil dilation or aging changes in the eye.
   
• Tumors, eye disease and other causes. A tumor behind the iris, swelling associated with inflammation of the ciliary body (intermediate uveitis) and alteration of the shape of the eye after retinal detachment surgery can also cause angle-closure glaucoma.
   

In addition to hyperopia, risk factors for acute angle-closure glaucoma include:

• Age. As we grow older, the lens inside our eyes gets larger, increasing the risk for pupil block. Also, the anterior chamber tends to become increasingly shallow, and the drainage angle may narrow as we age.
   
• Race. Asians and Eskimos, who have anatomically narrower anterior chamber angles than whites, have a higher incidence of angle-closure glaucoma.
   
• Sex. Among Caucasians, angle-closure glaucoma occurs three times more frequently in women than in men. Among African-Americans, men and women appear to be affected equally.

The goal of treatment is to reduce intraocular pressure as soon as possible. This can be done with systemic medications taken orally or sometimes given intravenously. Topical glaucoma eye drops are also often used to treat narrow-angle glaucoma. Frequently, laser and/or nonlaser glaucoma surgery may be required to reduce the IOP.

Remember that acute angle-closure glaucoma may be triggered by anything dilating the pupil, resulting in the iris blocking the angles. Dim lighting, eye drops administered by your eye care practitioner during an eye examination, or certain medications such as antihistamine/decongestant drops or cold medications may cause an acute angle-closure glaucoma attack.

In acute forms of glaucoma, optic nerve damage and vision loss will occur within hours if the angles of the interior eye structure are not opened to drain fluid and lower IOP.