If you experience any of these key symptoms, see a doctor ASAP.

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Glaucoma is often known as the "thief of sight"—and with good reason. The condition is actually a group of eye diseases that cause damage to the optic nerve, which is in the back of your eye and facilitates communication between your eye and your brain, according to the National Eye Institute (NEI). Optic nerve damage is irreversible, and glaucoma can eventually cause vision loss and blindness if left unchecked. So, naturally, eye doctors recommend routine glaucoma screening during your yearly eye exam, because catching it early is the best way to preserve your eyesight. 

angle closure glaucoma
Credit: Getty Images

There are multiple types of glaucoma—and angle-closure glaucoma is a particularly devastating one. While it's not the most common type, it's arguably the most important to look out for because it needs to be addressed ASAP. While other types of glaucoma, like open-angle glaucoma, progress at a slower rate, angle-closure glaucoma can sometimes cause a very fast and very intense increase in eye pressure and ultimately, damage to the eye.

Here's what you need to know about angle-closure glaucoma, including what it is, the main causes and risk factors, symptoms, and how it's treated.

What Is angle-closure glaucoma?

Also known as narrow-angle glaucoma, this type of glaucoma happens when the angle between the iris and cornea is either too narrow or completely closed off, blocking the drainage area of the eye, the NEI says. When fluid can't drain properly, eye pressure builds suddenly.

This type of glaucoma is more rare than open-angle glaucoma (, but it's arguably more dangerous because it can lead to an "attack," where the drainage becomes completely blocked. It's because of this that angle-closure glaucoma is sometimes considered a medical emergency, per the NEI.

Angle-closure glaucoma can be acute or chronic. Both types can have primary or secondary causes: Primary angle-closure glaucoma is caused by natural narrowing of the angle in the eye, whereas secondary is caused by a coexisting condition that impacts the eye angle, leading to this closure.

Acute angle-closure glaucoma

Acute angle-closure glaucoma causes a sudden and extremely high increase in eye pressure, Christopher Starr, MD, an. ophthalmologist at Weill Cornell Medicine and NewYork-Presbyterian, tells Health. This is called an angle-closure glaucoma attack. "That high high pressure usually is associated with symptoms, so a person would know it's happening," Dr. Starr says.

The NEI says you should get to the doctor or emergency room immediately if you experience the following symptoms:

  • Eye redness
  • Blurry or hazy vision
  • Severe eye or head pain
  • Nausea and vomiting

This type of acute angle-closure glaucoma is a medical emergency and requires immediate medical attention to relieve eye pressure and save the optic nerve from damage, Courtney Ondeck, MD, ophthalmologist in the Glaucoma Service at Mass Eye and Ear, tells Health.

Many times, an acute angle-closure attack has no discernible trigger. But one potential trigger is anything that causes your pupil to rapidly dilate. "It tends to happen if someone has a narrow angle and didn't know it, and then they go from a dark place to a light room or they take a drug that dilates the pupil," Dr. Ondeck says. "Things that tend to set it off tend to be things that dilate the pupil."

If the angle-closure episode resolves spontaneously, this is referred to as intermittent angle-closure glaucoma. But it's best not to bank on that happening—always call your doctor or go to an emergency room if you notice the symptoms of acute angle-closure glaucoma.

Chronic angle-closure glaucoma

Chronic angle-closure glaucoma happens when the angle narrows slowly. It doesn't cause a sudden and severe attack, because the eye pressure also rises slowly. "This could be from a previous acute angle-closure attack, or a very large lens that is pushing forward and causing scarring over a period of time," Dr. Ondeck says.

The lens in the eye actually gets bigger with normal aging, Daniel Laroche, MD, director of glaucoma services and president of Advanced Eyecare of New York and assistant professor of ophthalmology at the Mount Sinai School of Medicine, tells Health. "When that happens, it can sort of close off the drainage angle inside the eye and also rub up against the back portion of the iris that blocks the drain," he says. For some people, getting the lens removed can actually help open the drainage and be a good intervention for angle-closure glaucoma. Since many people develop cataracts (clouding of the lens) with age and need to have surgery to improve vision, it may make sense to get the lens removed early to help kill two birds with one stone, Dr. Laroche says.

Chronic angle-closure glaucoma is usually asymptomatic until significant vision loss occurs, similarly to open-angle glaucoma. Some people may experience eye redness, discomfort, blurred vision, or headache that improves with sleep, according to Merck Manual.

Secondary angle-closure glaucoma

If angle-closure glaucoma is caused by another condition, it's referred to as secondary. Both acute and chronic angle-closure glaucoma can have secondary causes.

Some health conditions can cause severe inflammation in the eye, which can cause scarring in the eye that closes the angle. Other health conditions that impact the eyes, including diabetic retinopathy and abnormal blood vessel growth, can also cause the angle to narrow and eventually close.

Eye injuries and surgeries that lead to scarring can also eventually close the angle and lead to angle-closure glaucoma.

What are the risk factors for angle-closure glaucoma?

"Risk factors tend to be older age, female sex, family history, being of East Asian descent, and farsightedness," Dr. Ondeck says. "Also having a cataract—the lens starts taking up more space, which takes space from the drainage system." The truth is, getting older and your genetics are the two biggest factors at play.

Your eye doctor can determine if you're an "angle-closure suspect" by doing a diagnostic exam called a gonioscopy. In this exam, your doctor will give you eye drops to numb the eye, and then place a special contact lens on the top of the eye. With your head positioned in a slit lamp (a small microscope with a very bright light), they can get a close-up look at the eye's drainage system. By assessing the drainage system and angle of the iris, your eye doctor can figure out if your eye angle is narrow, putting you at risk of angle-closure glaucoma.

Just because you have a narrow angle doesn't mean you'll end up with glaucoma. According to the Glaucoma Research Foundation, only 1 in every 10 to 20 angle-closure suspects will actually get the disease. But if your doctor knows you're at a higher risk, they'll be able to keep tabs on you and check in regularly to make sure that if it does become glaucoma, they can treat it immediately.

How is angle-closure glaucoma treated?

Acute angle-closure glaucoma requires emergency treatment—usually eye drops followed by a laser procedure—to bring down eye pressure, Dr. Ondeck says. Even if you intervene quickly, a closed-angle glaucoma attack can leave some nerve damage or scar tissue on the drainage system, which can increase the risk of a closure happening again.

Chronic angle-closure glaucoma is treated similarly to open-angle glaucoma, through various options of eye drops, laser treatments, and surgeries, depending on the severity. If the person also has a cataract, removing it can often help delay the glaucoma progression, according to Merck Manual.

After you're treated, your doc will still want to see you regularly to make sure that the angle is staying open, your eye pressure is in a healthy range, and your optic nerve looks good.

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