What Is A Glaucoma Attack Causes Symptoms Treatment?

A glaucoma attack, also known as acute angle-closure glaucoma, is a sudden and severe increase in pressure inside the eye. This happens when the eye’s drainage system gets blocked completely, causing fluid to build up rapidly. It is a medical emergency that can damage the optic nerve and lead to permanent vision loss within hours if not treated. The main causes are a sudden blockage of drainage canals, symptoms include intense eye pain and blurred vision, and treatment focuses on quickly lowering eye pressure with medication or laser surgery.

What Exactly Happens During a Glaucoma Attack?

Think of your eye like a sink with a drain. Fluid called aqueous humor normally flows in and drains out at a steady rate. During a glaucoma attack, the drain gets blocked. The iris, the colored part of your eye, pushes forward and closes off the drainage angle where fluid normally exits. This is why it is called “angle-closure.”

When the drain closes, pressure inside the eye skyrockets. Normal eye pressure ranges from 10 to 21 mmHg. During an attack, pressure can spike to 40, 50, or even 60 mmHg. That pressure crushes the optic nerve fibers. Research shows that damage can start within hours of this pressure spike. Some studies suggest that irreversible vision loss can occur after just 24 hours of sustained high pressure.

This condition is different from the more common open-angle glaucoma, which develops slowly over years. A glaucoma attack is sudden, painful, and obvious. You will know something is very wrong.

What Are the Symptoms of a Glaucoma Attack?

The symptoms come on fast and are hard to ignore. The most common sign is severe eye pain, often described as a deep ache or throbbing. This pain can spread to your head, causing a headache on the same side as the affected eye.

Other symptoms include:

• Blurry or hazy vision that does not clear with blinking
• Seeing rainbow-colored halos around lights, especially at night
• Redness in the white part of the eye
• Nausea and vomiting, which can be severe
• The eye feels hard to the touch, like a firm grape instead of a soft one

Some people report the affected pupil looks larger than the other eye, and it does not react to light normally. If you have these symptoms, do not wait. Go to an emergency room immediately. Do not try to sleep it off or wait for it to pass.

What Are the Main Causes and Risk Factors?

A glaucoma attack happens when the drainage angle closes, but certain people have eyes that are more prone to this. The biggest risk factor is having a shallow anterior chamber, meaning the space between your cornea and iris is smaller than average. This is often visible on an eye exam.

Other risk factors include:

• Being over age 40, with risk increasing significantly after 60
• Being female, as women have a higher risk than men
• Being of Asian or Inuit descent, due to differences in eye anatomy
• A family history of angle-closure glaucoma
• Farsightedness, because farsighted eyes tend to have shallower chambers

Certain medications can also trigger an attack in people who are already at risk. These include some cold medicines, antihistamines, and drugs used to dilate the eyes during an eye exam. Even dim lighting can trigger an attack in a susceptible eye because the pupil dilates, pulling the iris into the drainage angle.

How Is a Glaucoma Attack Diagnosed and Treated?

Diagnosis happens in an emergency room or an eye doctor’s office. The doctor will measure your eye pressure with a device that touches your eye after numbing drops. They will also look at your drainage angle using a special lens called a gonioscope. This confirms if the angle is closed.

Treatment is urgent and has two goals: lower the pressure immediately and open the drainage angle. The first step is usually medication. Doctors give eye drops like timolol or pilocarpine to reduce fluid production and open the angle. They may also give oral medications like acetazolamide, a pill that lowers eye pressure by reducing fluid throughout the body. In severe cases, an intravenous medication called mannitol pulls fluid out of the eye quickly.

Once the pressure starts to drop, the next step is a laser procedure called laser peripheral iridotomy. The doctor uses a laser to create a tiny hole in the iris. This hole provides a new pathway for fluid to flow, opening the drainage angle. The procedure takes only a few minutes and is done in the office. As of 2026, this laser treatment is the standard of care for preventing future attacks in the affected eye and the other eye.

If the pressure does not respond to medication or laser, surgery may be needed. A trabeculectomy creates a new drainage channel, or a drainage implant can be placed. These are less common for acute attacks but used when other treatments fail.

What Happens After Treatment and What Is the Outlook?

After the initial attack is treated, you will need ongoing care. The affected eye will need monitoring for the rest of your life. The other eye almost always gets a preventive laser iridotomy because it is at very high risk of having its own attack.

Vision loss from a glaucoma attack can be permanent. How much vision you lose depends on how high the pressure got and how long it stayed high. Some people recover full vision if treated within hours. Others lose peripheral vision permanently, even with successful treatment. Current research suggests that damage to the optic nerve can continue slowly even after the pressure is controlled, similar to open-angle glaucoma.

You will need regular eye exams every 6 to 12 months to check eye pressure and optic nerve health. Some people also need daily eye drops to keep pressure low long-term, even after the laser treatment. The key takeaway is that a glaucoma attack is a one-time crisis that requires lifelong follow-up.

What Should You Avoid If You Are at Risk?

If you know you have narrow angles or a shallow anterior chamber, there are things to avoid. Do not take over-the-counter cold or allergy medications without checking with your eye doctor first. Decongestants and antihistamines can dilate the pupil and trigger an attack.

Avoid spending long periods in dimly lit rooms. Your pupils dilate in low light, which can pull the iris into the drainage angle. If you feel eye discomfort in dim lighting, turn on more lights. Some people also find that certain sleeping positions, like lying face down, can increase pressure in the eye, though this is less clear from research.

Do not skip routine eye exams. A simple exam can detect narrow angles years before an attack happens. Your eye doctor can perform a preventive laser iridotomy if your angles are dangerously narrow. This is a quick, low-risk procedure that can save your vision. Many people choose to have it done in both eyes to eliminate the risk entirely.