Narrow Angle Glaucoma

5 min read

Glaucoma damages your optic nerve, which normally sends signals to your brain so you can see. Glaucoma is the leading cause of irreversible blindness. Glaucoma comes in many varieties. One serious but rare type of glaucoma is Narrow Angle Glaucoma which sometimes is also called Angle Closure Glaucoma. Narrow angle glaucoma is different from the most common form of glaucoma, known as open angle glaucoma. While open-angle glaucoma unfolds over years, narrow angle glaucoma can be acute, where it happens suddenly, or it can also be chronic, where it happens over a longer time.  The difference between narrow angle glaucoma and open angle glaucoma is the way in which a person's eye is shaped.

Narrow Angle Glaucoma

Everything that happens in narrow-angle glaucoma can be understood by understanding the name. Your eye's "angle" rests between the eye's natural drainage system, known as the trabecular meshwork, and the iris. Narrowing or closure of this angle results in a clogging of the drainage system. As a result, fluid pressure builds up in the eye. This rapidly alters one's vision and can progress to blindness within a day.

Glaucoma Symptoms In Narrow Angle

Symptoms of acute narrow-angle glaucoma include sudden eye pain, red eye, blurry vision, rainbows, nausea, vomiting, and headaches. This is a medical emergency that could result in permanent vision loss if not treated quickly. If you have these symptoms, you should see an eye doctor immediately, or go to an emergency room where you can get medications to lower your eye pressure.

Chronic narrow angle glaucoma occurs over time. It does not usually present with the above sudden symptoms. Instead, it presents asymptomatically on routine exam. The doctor may see tissue adhesions (known as synechiae) formed between your iris and trabecular meshwork. They may also note an increasing eye fluid pressure (known as "intraocular pressure," or IOP). 

Diagnosis of Narrow Angle Glaucoma

If you have the above symptoms, your eye doctor will want examine you further. They will first want to take a look into the front part of your eye to visualize your eye drainage angle. This is done with an instrument called a gonioscope. The angle of the eye is the part of the eye that drains the fluid from the eye. When the angle is narrow, you have an anatomically narrow angle. This shape of the drainage system can then lead to narrow angle glaucoma.

Who Is At Risk For Narrow Angle Glaucoma

Some people just have an anatomically narrow angle. Other people may develop one over time or due to trauma. With age, the lens within our eyes enlarges, and this can push up on the iris, which narrows the angle. Physical injury to the eye can also dislocate the lens, causing narrow-angle glaucoma. Some patients are born with anatomic differences that decrease their eye angle. Patients at risk for narrow angle glaucoma include those with smaller eyes (resulting in far-sightedness), older age, female sex, Asian and Native American ethnicity, or having a family history of angle-closure. Chronic narrow-angle glaucoma may occur over time in patients when tissue adhesions form between the iris and trabecular meshwork. 

Glaucoma Testing

The eye doctor will do a gonioscopy exam, in which they place a large lens onto your eye to take a direct look at the angle of your eye. Your doctor will also peer through a slit-lamp microscope to look at the entire front part of your eye. They will use a ophthalmoscope to look at your optic nerve to see if there is damage. Doctors may also check how good your peripheral vision is through a testing of your visual fields. They can also in office scan, called an OCT, or an ultrasound (UBM) of your eye to look at your optic nerve or eye angle. 

Narrow Angle Glaucoma Treatment

In healthy eyes, IOP is 10-21 mm Hg. Glaucoma is defined by elevated IOP. Acute narrow-angle glaucoma usually presents with a sudden increase in IOP >40 mm Hg due to the obstruction of the drainage angle. As mentioned above, such increased pressure in the eye may damage the optic nerve. 

Medical treatment for acute narrow-angle glaucoma should first quickly lower your fluid pressure levels (IOP) to prevent further damage to the optic nerve. Your doctor can use topical eye drops including various classes of beta blockers, selective alpha agonists, carbonic anhydrase inhibitors,  amongst others. They may also use systemic therapy like mannitol or oral osmotic agents.

The next step in the treatment of narrow-angle glaucoma, both acute and chronic, is a laser iridotomy. An eye surgeon will use a laser to make a small pinhole in your iris. Fluid flows through this hole and fixes the drainage problem. If you have a narrow angle in one eye, your other eye is also at risk. Your surgeon will perform the same procedure in the other eye as well to prevent future attacks. Your IOP will be routinely monitored as an extra method of prevention.


Sources: 

https://glaucoma.org/are-you-an-angle-closure-glaucoma-suspect/

https://glaucoma.org/what-is-angle-closure-glaucoma/?print=print

https://eyewiki.aao.org/Primary_vs._Secondary_Angle_Closure_Glaucoma

https://www.aao.org/munnerlyn-laser-surgery-center/angleclosure-glaucoma-19

https://www.aoa.org/healthy-eyes/eye-and-vision-conditions/glaucoma?sso=y

 

© 2022 eyeFACTS. All Rights Reserved.