Acute Glaucoma (Acute Angle-Closure Glaucoma)

How acute glaucoma happens

The front of the eye is filled with a clear fluid called aqueous humor. It is made behind the iris, flows through the pupil, and drains out through the drainage angle, where the iris meets the cornea.

In some eyes, the angle is naturally narrow. If the iris bulges forward or thickens, for example when the pupil is mid-dilated in dim light, it can suddenly seal the angle. Fluid keeps being made but cannot leave, so pressure rises quickly, often from a normal 10 to 21 mmHg to 40 to 80 mmHg within hours. This pressure squeezes the optic nerve and swells the cornea.

Symptoms of acute glaucoma

• severe, aching eye pain, often around or behind the eye
• a red eye
• blurred or hazy vision
• rainbow-colored halos around lights
• headache on the same side
• nausea and vomiting, sometimes mistaken for a stomach problem or migraine
• a mid-dilated pupil that does not react to light
• an eye that feels hard to the touch

Symptoms usually affect one eye. Some people have intermittent episodes first: short bouts of blurring, halos and ache in dim light that clear after sleep. These are warnings that a full attack may follow.

Risk factors

• Age over 50, as the lens thickens and pushes the iris forward
• Female sex
• Farsightedness (hyperopia), which means a smaller eye with a shallower front chamber
• East Asian or Inuit ancestry
• Family history of angle-closure glaucoma
• Cataract that has become thick

Triggers

• dim light, darkness, cinemas
• dilating eye drops used during eye exams (risk is small, and screening exams are still recommended)
• medicines that widen the pupil or shift the lens: decongestants, antihistamines, anticholinergics, some antidepressants (tricyclics, SSRIs), topiramate (which causes a different type of angle closure, usually in both eyes), and some inhalers
• emotional stress

Many medicine leaflets warn against use "if you have glaucoma". This warning is about angle-closure risk; it usually does not apply to people with the common open-angle type of glaucoma.

Acute glaucoma vs other painful red eyes

Other causes of a painful red eye, such as conjunctivitis and uveitis, look different:

How it is diagnosed

An ophthalmologist or ER doctor will:

• measure eye pressure (tonometry)
• examine the eye with a slit lamp: cloudy cornea, shallow front chamber, mid-dilated pupil
• gonioscopy: a special lens to view the drainage angle and confirm closure
• examine the other eye, which usually has a narrow angle too
• check the optic nerve once the cornea clears

Treatment

Emergency treatment

The aim is to lower pressure as fast as possible:

• eye drops: beta-blockers (timolol), alpha-agonists (apraclonidine or brimonidine), and pilocarpine once pressure has started to fall
• acetazolamide by mouth or IV to reduce fluid production
• osmotic agents such as IV mannitol for very high pressure
• steroid drops for inflammation
• pain relief and anti-nausea medicine

Definitive treatment

• Laser peripheral iridotomy (LPI): a laser makes a tiny hole in the iris, letting fluid bypass the blocked pupil and the iris fall back, opening the angle. It is done in the affected eye once the cornea clears, and usually in the other eye too, as prevention, since about half of fellow eyes would otherwise have an attack within 5 years.
• Lens extraction (cataract surgery): removing the thick natural lens deepens the front chamber and is an effective first-line or follow-on treatment, particularly with cataract.
• Glaucoma surgery if pressure stays high despite these.

Outlook

When pressure is lowered within hours, most people recover good vision. Delay can cause permanent loss of vision from optic nerve damage, scarring of the drainage angle, and chronic glaucoma that needs lifelong treatment. Regular eye checks continue after treatment.

Prevention

• Get regular eye exams after 40, especially if you are farsighted, of East Asian descent, or have a family history.
• If you are told you have narrow angles, ask whether preventive laser iridotomy is advised, and check medicines with your doctor or pharmacist.
• Know the warning symptoms and seek care immediately.

Frequently asked questions

What are the symptoms of acute glaucoma?

Acute glaucoma causes sudden, severe eye pain, a red eye, blurred vision, rainbow halos around lights, headache, nausea and vomiting. The pupil may look mid-dilated and not react to light. It is an emergency that needs treatment within hours.

Can acute glaucoma cause permanent blindness?

Yes. Very high pressure can damage the optic nerve within hours to days, causing permanent vision loss. Rapid treatment to lower the pressure, followed by laser iridotomy, usually saves vision. Do not wait to see if it settles.

What triggers an angle-closure attack?

Common triggers are dim light, dilating eye drops, and medicines such as decongestants, antihistamines, some antidepressants and topiramate. Stress can also contribute. Attacks happen mainly in people with naturally narrow drainage angles.

Is acute glaucoma the same as regular glaucoma?

No. The common form, open-angle glaucoma, develops slowly and painlessly over years. Acute angle-closure glaucoma is a sudden blockage of drainage with a rapid pressure spike, severe pain and vision loss, and it is an emergency.

How is acute angle-closure glaucoma treated?

Doctors lower the pressure urgently with eye drops, acetazolamide and sometimes IV medicines. Once the eye settles, a laser makes a small hole in the iris (laser iridotomy) to keep the drainage open. The other eye is usually treated too.