Under Pressure: Attacks of Narrow-Angle Glaucoma

Narrow-angle glaucoma, also called NAG or closed-angle glaucoma, is the second most common form of glaucoma and usually presents through sudden attacks of pain caused by increased eye pressure where the iris – the colored portion of your eye – is pushed forward.

The sudden pressure change can create blockages in the eye’s drainage angle, preventing the outflow of fluid from your eye.

Blockages increase the internal pressure on the eye – intraocular pressure (IOP) – and can cause damage to the optic nerve and its ability to process and transit images between the eye and brain.

Narrow Angle Glaucoma

Some people are born with narrow drainage angles, making them at greater risk for NAG and making its onset easier.

For example, the Mayo Clinic says that sudden dilation of your pupils may be enough to trigger an acute case of NAG for people with naturally shallow drainage angles.

Symptoms and Warnings

Between these sudden attacks, the pressure on the eye is normal and there are no symptoms.

When the attacks happen, NAG can cause various symptoms, including:

  • Blurred vision
  • Eye pain,
  • Dilated pupils,
  • Headaches,
  • Red eyes,
  • Nausea,
  • Unusual halos around lights,
  • Vision loss, or
  • Vomiting.

The signs may last for hours or until the pressure subsides. These attacks are extremely serious and you should seek medical attention if they happen. Each attack has the potential to damage your peripheral vision.

If left untreated, NAG can cause blindness in a few days, according to the Southland Eye Clinic and All About Vision. It is recommended to immediately seek out an emergency room or an ophthalmologist.

There are also some forms of chronic NAG that can cause slow, subtle damage to the eye and vision because the pressure is not great and builds up over time. This type of NAG causes little pain or vision problem in its early stage but can become painful as it progresses, leading to permanent damage.

Narrow-Angle Glaucoma Causes

Doctors do not fully understand the exact nature of the increase in intraocular pressure and related blockages, but there are some causes doctors look at when trying to diagnose NAG. These include:
  • Eye tumors. Growths in the eye, such as tumors that develop behind the iris, cause swelling, inflammation, and pressure in the eye. They can also cause the ciliary body to change shape, increasing pressure and the risk of developing NAG.
  • Hyperopia. People who are diagnosed as being farsighted are also at a higher risk for developing NAG. This is because they tend to have shallow anterior chambers and narrow drainage angles, increasing the risk of acute NAG attacks when pupils dilate.
  • Iris plateau. Your eye uses what’s called the trabecular meshwork to drain its fluid. If, such as in this condition, the iris is connected to the ciliary body to close to this network, tissue can build up and block the network. For this condition, when the pupil dilates more tissue builds up and eventually the drainage angle is blocked, increasing intraocular pressure. An iris plateau-related attack can occur in low-light situations and when the pupils are enlarged on purpose, such as during an eye exam.
  • Medicines. People prone to NAG, or having experienced an acute attack in the past, should avoid many cold remedies containing Pseudoephedrine as well as some anti-histamines like Benadryl. These medicines can increase your risk of an attack and often have warning labels on their boxes.
  • Natural predisposition. Some people are born with naturally narrow or shallow drainage angles, making them more prone to have fluid or tissue build up and block the channel. This means they are more included to experience NAG and the likelihood of an acute NAG attack rises with age.
  • Pupillary blockages. The eye produces its own special fluid, called the aqueous humor, in the ciliary body and eye muscles help this flow through the pupil into the front and back of your eye. Sometimes the iris can become stuck to the eye’s lens, blocking the pupillary channel that allows this fluid to pass through the iris. If this occurs, pressure builds and will push the eye forward, eventually blocking the drainage angle.
  • Steroid use. Steroid use – both for weightlifting and for medicinal purposes – can also cause an increase in eye pressure. Pressure from steroid use has been definitively linked to some glaucoma types, though it is unclear if it plays a role in NAG.

Risk Factors

Age, race, and sex all play a role in your risk for narrow-angle glaucoma.

As everyone grows older, the lenses inside their eyes get larger while the anterior chamber gets smaller. This slowly increases the chance for a pupil blockage and drainage angle blockage over time.

Some races are also more prone to developing NAG. Inuit people and others indigenous to Canada and northern United States, as well as those of Asian heritage, tend to have smaller anterior chambers and drainage angles, raising the NAG risk.

Sex appears to play a role for Caucasians, with women experiencing NAG three times more often than men, according to the Mayo Clinic.


There are a variety of treatments for acute NAG, all of which aim to reduce pressure in a safe, and quick manner. Many hospitals and emergency rooms will provide medicine in the form of pills, IVs, or eye drops. Some eye drops used to treat other forms of glaucoma have been found to be effective for treating acute NAG.

For some cases, surgery may be required to treat NAG because other methods do not relieve enough intraocular pressure. This can be done either in a hospital or in an ophthalmologist’s office. In-office laser surgeries involve creating a small hole in the eye to help drain excess fluid.

Surgeries are typically painless and have a high success rate. In rare cases, openings made by laser surgeries can close after time. This can lead to new NAG attacks. Some patients who have surgery and take medicines afterward have seen adverse reactions to glaucoma and other medications.

If you or your loved one experiences an NAG attack or anything similar, seek immediate medical attention because these can lead to damage or even death of optic nerve fibers. Under current understanding, when nerve fibers die there is no way to undo associated damage.


Comments (2)

  • A.A. Sokoloski


    I have some confusion about acceptable pressure levels for wide angle as opposed to acceptable levels for NAG. From what I can glean from non technical literature summaries it seems like there are two standards used for triggering action, with the wide angle standard running as high as 30 before action is recommended whereas 20 is considered high for NAG. Is the NAG standard the same for those who has experienced a near emergency pain episode as compared to those who have not but have merely had NAG diagnosed as part of a regular exam?







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