Understanding Narrow Angles
The eye continually produces aqueous humor, a clear fluid that maintains internal pressure. This fluid is made by the ciliary body, located behind the iris, the colored part of the eye. Aqueous humor then flows between the iris and the lens, passes through the pupil, and reaches the front of the eye.
For proper eye function, aqueous humor must drain at a balanced rate to prevent pressure buildup. Drainage primarily occurs through the trabecular meshwork, located in the drainage angle where the iris and cornea meet.
A “narrow angle” describes an anatomical configuration where this drainage space between the iris and the cornea is reduced. The iris sits unusually close to the trabecular meshwork, impeding the normal outflow of aqueous humor. This can block the meshwork, leading to insufficient fluid drainage and predisposing an individual to certain eye conditions.
Why Narrow Angles Matter
Narrow angles can interfere with the eye’s fluid drainage system. Reduced space between the iris and cornea prevents aqueous humor from exiting efficiently, causing intraocular pressure (IOP) to increase.
Elevated IOP is a primary concern because it can damage the optic nerve, which transmits visual information from the eye to the brain. Damage to the optic nerve can lead to irreversible vision loss. While narrow angles indicate a predisposition, they do not automatically mean angle-closure glaucoma. This condition occurs when the drainage angle closes, causing pressure to build.
Angle closure manifests in two forms: acute or chronic. Acute angle-closure glaucoma is a sudden and severe event where the angle completely blocks, leading to a rapid and significant rise in eye pressure. Symptoms include severe eye pain, headache, blurred vision, and seeing halos, requiring immediate medical attention to prevent permanent vision loss. Chronic angle-closure glaucoma develops gradually as the angle slowly narrows, potentially leading to scarring and a progressive IOP increase.
How Narrow Angles Are Detected
Detecting narrow angles requires a specific eye examination, as symptoms may not appear until an acute event. Regular comprehensive eye exams are important for identifying this predisposition.
The primary method to assess the drainage angle is gonioscopy. During this procedure, an eye care specialist uses a special mirrored lens, often with a slit lamp, to directly visualize the anterior chamber angle. This allows the doctor to determine if the angle is open or narrow and to identify any potential blockages or abnormalities.
Optical Coherence Tomography (OCT) can supplement gonioscopy. Anterior segment OCT provides detailed cross-sectional images of the front of the eye, allowing precise measurements of angle width and other anatomical features. These methods help professionals assess angle closure risk and guide management.
Managing Narrow Angles
Once narrow angles are detected, management focuses on preventing a sudden rise in eye pressure. For individuals with narrow angles but no glaucoma signs, laser peripheral iridotomy (LPI) is a common preventive procedure. This outpatient procedure involves using a laser to create a tiny, unnoticeable hole in the iris.
This opening creates an alternative pathway for aqueous humor to flow from the back of the iris to the front, which helps to widen the drainage angle. This prevents the iris from blocking the trabecular meshwork and significantly reduces the risk of angle-closure glaucoma.
In acute angle-closure attacks, immediate treatment is necessary to lower rapidly elevated intraocular pressure. This often involves medications to reduce eye pressure, followed by an LPI once pressure is controlled. Early detection allows for proactive intervention, potentially preventing vision-threatening complications.
Who Is Susceptible
Several factors increase susceptibility to narrow angles. Age is a contributing factor, as the condition becomes more prevalent in older adults when the eye’s lens thickens and pushes the iris forward.
Ethnicity also plays a role, with a higher incidence in individuals of East Asian and Inuit descent. Anatomical predispositions, such as being farsighted (hyperopic), are associated with narrow angles because hyperopic eyes tend to be smaller, leading to crowded internal structures. A family history of narrow angles also indicates an increased potential risk.