Causes of Narrow-Angle Glaucoma

Acute narrow angle glaucoma occurs primarily in patients who have a shallow space between the cornea at the front of the eye and the colored iris that lies just behind the cornea. As the eye ages, the natural lens behind the pupil grows and the pupil becomes smaller, restricting the flow of fluid to the drainage site. Fluid can build up behind the iris, pushing it forward and blocking the channel (angle) that normally allows aqueous fluid to drain. If blockage happens, a rapid rise in intraocular pressure can occur.

• Pupillary block.  Eye fluid known as the aqueous humor is 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.
• Hyperopia. People who are farsighted are more likely to have eyes with shallow anterior chambers and narrow angles, increasing their risk for angle-closure glaucoma from pupil dilation or aging changes in the eye.
•  Hypertension. A number of studies also suggest a possible correlation between hypertension and the development of glaucoma.  
• People with small eyes. People with small eyes are predisposed to developing closed-angle glaucoma because they tend to have narrow filtering angles. Small eyes are not obvious from their appearance, but they can be measured by an eye doctor.

Diabetes can be a contributing cause to the development of glaucoma.

Who is at risk for narrow angle glaucoma?

Although anyone can be diagnosed with narrow angle glaucoma, there are some characteristics that make people more susceptible than others. Major risk factors for narrow angle glaucoma include:

• Age. Angle recession glaucoma usually occurs in people that are over 40 years of age.
• Gender. Women more often are diagnosed with angle recession glaucoma than men.
• Ethnicity. Asians, as well as Inuits and other northern indigenous people, who have anatomically narrower anterior chamber angles than whites, have a higher incidence of angle-closure glaucoma.