Narrow-Angle Glaucoma: Signs, Causes, and Treatment

Narrow-angle glaucoma occurs when the drainage angle, a structure that allows the fluid within your eye to drain normally, becomes blocked. It can happen quickly or slowly and progressively. A comprehensive eye exam can detect it.

Doctors diagnose the condition primarily through gonioscopy, but they can also use ultrasound biomicroscopy and anterior segment optical coherence tomography. 

Untreated, the condition can cause a total loss of vision. The treatment regimen includes topical medications, cataract surgery and laser surgery.

What is Narrow-Angle Glaucoma?

Narrow-angle glaucoma occurs when the drainage angle formed by the iris and cornea becomes blocked. The fluid within the eye backs up as the angle gets smaller, increasing intraocular pressure (pressure in the eye). Elevated intraocular pressure is associated with optic nerve damage and loss of visual field.

Narrow-angle glaucoma can be acute, which occurs when the drainage angle is blocked and causes eye pressure to rise rapidly, or chronic, which develops slowly.

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Symptoms

Individuals with narrow-angle glaucoma may not experience any symptoms before an acute attack. Early signs of an attack include:

• Blurred vision
• Headache
• Sudden severe head and eye pain
• Red eyes
• Seeing halos or rainbow-colored rings around lights
• Pupil becomes mid-dilated
• Nausea
• Vomiting

You should seek treatment immediately for an acute attack.

Causes

If untreated, narrow-angle glaucoma can cause a total loss of vision.

Scientists attribute most cases of narrow-angle glaucoma to pupillary block, during which aqueous pushes the pupil forward. Narrow-angle glaucoma is also usually associated with the following conditions:

• Plateau iris: Patients with plateau iris have an abnormal configuration of the ciliary body — a structure behind your iris that produces aqueous fluid in your eye. The ciliary body is so far forward, resulting in the peripheral iris being pushed forward and a reduced drainage angle.
• Tumors and other eye disorders: A tumor behind your iris can cause narrow-angle glaucoma. Disorders of the lens, vitreous and retina, and ciliary cysts are also potential causes of narrow-angle glaucoma.
• Surgery: Narrow-angle glaucoma can occur after undergoing surgery that causes changes to the structure of your eye.
• Medication: Over-the-counter and prescription medications can contribute to the development of narrow angles. For example, antihistamines and antidepressants can increase your risk for narrow-angle glaucoma by anteriorly displacing the lens-iris diaphragm or inducing iris dilation. Topiramate, which is used to treat migraines, epilepsy, and for weight loss, can cause swelling of the lens and ciliary body.

Diagnosis

Eye doctors can diagnose narrow-angle glaucoma with a comprehensive eye examination. The diagnostic tests commonly relied on are gonioscopy, anterior segment optical coherence tomography (AS-OCT) and an ultrasound biomicroscopy.

Gonioscopy is the standard for diagnosing narrow-angle glaucoma, and it features a special contact lens known as a gonioprism. The doctor gently places the lens on the eye and uses the mirror on the lens to check whether the angle between the cornea and iris is narrow.

Ultrasound biomicroscopy imaging technology, which combines light with a low-power microscope, allows a section of the eye’s filtering part to be seen in detail. AS-OCT devices provide images of the eye’s anterior segment.

Treatments

It is best to begin narrow-angle glaucoma treatment as soon as possible. Treatment options include eye drops, cataract surgery, iridotomy and Iridoplasty.

Even though narrow-angle glaucoma treatments can produce successful and long-lasting results, you should get regular checkups because chronic glaucoma can still occur.

Eye Drops

Doctors typically prescribe beta blockers as the first eye-drop treatment for glaucoma. Drops are affordable and bring few serious side effects.

However, beta blockers can interfere with someone (knowingly or not) comping with hypoglycemia. Someone with diabetes may not be a good candidate for drops.

Miotics are another class of eye drop doctors prescribe. They reduce the pressure in the eye by increasing the angle between the iris and the cornea, prompting better fluid drainage.

Cataract Surgery

Cataract surgery replaces the eye’s natural lens with a clear implant lens. It can effectively lower eye pressure in some narrow-angle glaucoma patients.

Iridotomy

Iridotomy is a common procedure for narrow-angle glaucoma patients because it helps lessen pupillary block. It is a type of laser surgery where surgeons make a small hole in the iris. The hole enhances the outflow of fluid, lowering eye pressure and reducing the risk of angle closure.

Surgeons can also use laser iridotomy as a preventive treatment for someone who is a candidate to develop narrow-angle glaucoma. But not everyone with narrow drainage angles develops glaucoma.

Doctors evaluate the angle structure as well as other risk factors to determine who is at the greatest risk of developing glaucoma to decide whether preventive treatment is necessary.

Iridoplasty

Iridoplasty involves using a laser to shrink your iris away from your drainage angle. Doctors usually perform this procedure on patients who need further intervention.

Outcomes

Laser iridotomy can successfully treat narrow-angle glaucoma resulting from a pupillary block. When laser iridotomy is performed on patients with plateau iris, it usually opens a very small amount of the angle. Therefore, if other mechanisms like plateau iris syndrome are behind your narrow-angle glaucoma, you may need further intervention like laser iridoplasty.

Even though narrow-angle glaucoma treatments can produce successful and long-lasting results, you should get regular checkups because chronic glaucoma can still occur.

Prevention

Narrow-angle glaucoma can be prevented using laser iridotomy. The small hole punched in the peripheral iris during laser iridotomy acts like a safety valve that deflates the pressure behind your iris.

If an ophthalmologist notes a critically narrow angle in your eye before you develop glaucoma symptoms, he or she can recommend laser iridotomy to provide protection from narrow-angle glaucoma.

FAQs

Is narrow-angle glaucoma serious?

Narrow-angle glaucoma is serious because if it is not diagnosed and treated, it can lead to permanent vision loss.

Untreated narrow-angle glaucoma can result in a sudden acute-angle glaucoma attack. Acute episodes of narrow-angle glaucoma are associated with elevated eye pressure and pain and are a medical emergency. If you fail to get timely treatment for acute-angle glaucoma, your risk of some permanent loss of vision increases.

Is there a cure for narrow-angle glaucoma?

Treatments for narrow-angle glaucoma can yield long-lasting results. However, the sooner the condition is diagnosed and treated, the higher your chances of having healthy eyes and clear vision.

References

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8. Diagnosing and managing patients with narrow angles. (December 2017). Optometry Times.

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14. Case Studies: Cataract Surgery for Narrow-Angle Glaucoma. (August 2014). Cleveland Clinic.

15. What Is Glaucoma? Symptoms, Causes, Diagnosis, Treatment. (September 2021). American Academy of Ophthalmology.

16. Glaucoma Surgery and Laser Treatments (Video). (July 2020). Glaucoma Research Foundation.

17. What Is Chronic Angle-Closure Glaucoma? (December 2021). American Academy of Ophthalmology.

18. Angle-Closure Glaucoma. (December 2018). Glaucoma Research Foundation.

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22. Miotic. Oxford Reference.