A glaucoma attack, known medically as acute angle-closure glaucoma, is a sudden spike in eye pressure that can cause permanent vision loss within hours if untreated. Normal eye pressure ranges from 14 to 17 mmHg; during an attack, pressure can surge to 40, 60, or even higher. It happens when the colored part of your eye (the iris) shifts forward and physically blocks the eye’s internal drainage system, trapping fluid inside.
Unlike the more common form of glaucoma, which develops slowly over years with no symptoms, a glaucoma attack hits fast and hard. It is a true eye emergency.
How Fluid Gets Trapped in the Eye
Your eye constantly produces a clear fluid that flows from behind the iris, through the pupil, and out through a ring-shaped drainage channel where the iris meets the white of the eye. In a glaucoma attack, the iris bows forward and seals off this drainage angle. When at least 270 degrees of that ring is blocked, fluid has almost nowhere to go. Pressure builds rapidly inside the eye, and that pressure starts damaging the optic nerve, the cable that carries visual information to your brain.
The most common trigger is something called pupillary block. Fluid trying to pass from behind the iris through the pupil meets resistance, and the buildup of fluid behind the iris pushes it forward like a sail catching wind. This closes the drainage angle and sets the attack in motion. Dim lighting, certain medications that dilate the pupil (like some antihistamines or antidepressants), and even emotional stress can trigger an episode in a susceptible eye.
What a Glaucoma Attack Feels Like
The symptoms are intense and usually impossible to ignore:
- Severe eye pain that may radiate across the forehead
- Bad headache, often on the same side as the affected eye
- Nausea or vomiting, which sometimes leads people to mistake it for a stomach illness or migraine
- Blurred vision that comes on suddenly
- Halos or colored rings around lights
- Eye redness
The combination of nausea, headache, and vomiting is what makes this tricky. People sometimes show up at an emergency room thinking they have a migraine or food poisoning, and the eye problem gets overlooked. The key distinguishing signs are the one-sided eye pain, visible redness, and halos around lights. If you experience these together, tell the medical team you’re concerned about your eye specifically.
Who Is Most at Risk
Glaucoma attacks don’t happen to everyone equally. Certain eye anatomy makes some people far more vulnerable. People with naturally shallow anterior chambers (the fluid-filled space behind the cornea), thicker lenses, or smaller eyes are more prone because their drainage angle is already narrow before anything goes wrong. It only takes a small shift of the iris to close it off entirely.
Age is the biggest risk factor. Glaucoma prevalence jumps from about 1% among adults aged 40 to 64 to nearly 8% among those over 80. Women are affected more often than men, partly because they tend to have slightly smaller eyes with narrower angles. People of East Asian descent have higher rates of angle-closure glaucoma specifically, while Black adults in the U.S. are roughly twice as likely as white adults to have glaucoma overall and nearly three times as likely to have the vision-affecting form.
Farsightedness is another risk factor, because farsighted eyes tend to be shorter, crowding the structures at the front of the eye and narrowing the drainage angle.
Why Quick Treatment Matters
Every hour of sky-high eye pressure chips away at the optic nerve. Nerve fibers that die during an attack don’t regenerate, so any vision lost is permanent. The prognosis depends heavily on how quickly pressure is brought down. One study found that patients who received definitive treatment within seven days of symptom onset were more than four times as likely to have a successful outcome compared to those treated later.
This is why a glaucoma attack is classified as an ophthalmologic emergency. If you suspect one, go to an emergency room or contact an eye doctor immediately.
What Happens at the Hospital
The first priority is lowering eye pressure as fast as possible. You’ll typically receive a combination of eye drops that reduce fluid production and help open drainage pathways, along with a medication to pull fluid out of the eye from the inside. You may also receive drops that constrict the pupil, physically pulling the iris away from the drainage angle. If nausea is severe, anti-nausea medication is given so you can tolerate the oral medications.
Most people feel significant relief within the first hour or two as the pressure starts to come down. The eye may remain sore and your vision somewhat blurry for days afterward, but the intense pain typically subsides once pressure normalizes.
Laser Treatment to Prevent Future Attacks
Once the acute pressure is controlled, the standard next step is a procedure called laser peripheral iridotomy. An eye specialist uses a laser to create a tiny hole in the iris, giving fluid a new pathway to flow through. This bypasses the pupillary block mechanism and prevents the iris from bowing forward again.
The procedure takes just a few minutes, is done in an outpatient setting, and requires only numbing eye drops. Success rates for iridotomy range from about 60% to 76%, depending on the study and the population. In one study of 77 eyes, about 60% had normal pressure after iridotomy alone. The remaining 40% needed additional pressure-lowering drops or further procedures.
Timing matters here, too. Eyes treated sooner after an attack respond better to iridotomy. In patients who had more than a 30% drop in pressure after the procedure, over 92% maintained normal pressure long-term. Most cases where pressure crept back up did so within six months, so follow-up visits during that window are important.
The other eye typically receives a preventive iridotomy as well, since the anatomy that caused the attack in one eye is usually mirrored in the other.
How the Diagnosis Is Confirmed
Beyond measuring eye pressure, the key diagnostic tool is gonioscopy. Your eye specialist places a small mirrored lens on the surface of your numbed eye and uses it to peer around the curve of the cornea into the drainage angle, like angling a mirror to see around a corner. If the angle is narrow or closed, that confirms the diagnosis. This exam takes only a minute or two and is painless, though the contact with the eye surface can feel slightly odd.
Gonioscopy also helps determine whether the angle closure is caused by pupillary block or by a less common mechanism, which influences the treatment approach. If you have a family history of glaucoma or have been told you have “narrow angles,” periodic gonioscopy can catch problems before an attack ever occurs.
Long-Term Outlook After an Attack
With prompt treatment, many people retain good vision after a glaucoma attack. The amount of permanent damage depends on how high the pressure went and how long it stayed elevated. Some people walk away with no noticeable vision changes; others have lasting blind spots or reduced peripheral vision.
After an attack, you’ll need ongoing monitoring. About 15% of patients develop chronic angle-closure glaucoma even after the acute episode resolves, requiring long-term pressure-lowering drops. Your eye specialist will check pressure, drainage angle status, and optic nerve health at regular intervals to catch any slow-building damage early.