Acute Glaucoma – What You Need to Know

What is Glaucoma (acute)?

Acute glaucoma, most commonly referred to as acute angle‑closure glaucoma (AACG), is a rapid increase in intra‑ocular pressure (IOP) that occurs when the drainage angle of the eye suddenly becomes blocked. The blockage prevents aqueous humor (the fluid that nourishes the front of the eye) from exiting, causing pressure to rise within minutes to hours. This sudden pressure spike can damage the optic nerve and lead to permanent vision loss if not treated immediately.

Unlike the “open‑angle” form that progresses slowly over years, acute glaucoma is an ophthalmic emergency. It typically affects one eye at a time, often in people over age 50, and can be triggered by anatomical predisposition, certain medications, or eye‑related events.

Sources: Mayo Clinic; American Academy of Ophthalmology (AAO) [1][2]

Common Causes

Acute angle‑closure glaucoma results from anything that narrows or blocks the anterior chamber angle. The most frequent precipitating factors include:

• Anatomically narrow angle – a shallow anterior chamber, common in hyperopic (farsighted) eyes.
• Pupil‑dilating medications – antihistamines, antidepressants, anticholinergics, and some eye drops.
• Dark‑adaptation – pupils enlarge in low‑light environments, increasing angle closure risk.
• Posterior subcapsular cataract – pushes the iris forward, narrowing the angle.
• Eye trauma – blunt or penetrating injuries can cause swelling of iris tissue.
• Inflammatory conditions – uveitis or iritis leading to synechiae (adhesions) that close the angle.
• Systemic medications – diuretics or sulfonamide drugs that cause ocular edema.
• Topical corticosteroids – long‑term use may thicken the lens and narrow the angle.
• Pregnancy – hormonal changes and fluid shifts can precipitate angle closure in predisposed women.
• Sudden ocular hypotony – rapid decrease in pressure after eye surgery can cause the iris to bow forward.

While any of these factors can act alone, many patients have a combination of anatomical predisposition plus a trigger (e.g., taking a cold‑medicine antihistamine in a dimly lit room).

Associated Symptoms

Symptoms often appear abruptly and may be severe. Common accompanying signs include:

• Severe, throbbing eye pain (usually unilateral)
• Redness of the conjunctiva (pink eye)
• Blurred or “halo” vision around lights
• Marked decrease in visual acuity—sometimes described as a “cloudy” view
• Headache, often frontal or temporal
• Nausea and vomiting (due to pain and autonomic response)
• Pupillary dilation that does not react to light (mid‑dilated, fixed pupil)
• Feeling of “pressure” around the eye

These symptoms develop quickly, usually within minutes to a few hours, and can be mistaken for migraines or sinus pain, which makes awareness crucial.

When to See a Doctor

Because acute glaucoma can cause irreversible vision loss within 24–48 hours, err on the side of caution. Seek immediate medical attention if you experience any of the following:

• Sudden, severe eye pain that does not improve with over‑the‑counter pain relievers.
• Rapid loss of vision or appearance of halos around lights.
• A red eye accompanied by nausea or vomiting.
• Any change in vision after using pupil‑dilating drops, antihistamines, or after a dark‑room exposure.
• History of narrow angles or previous glaucoma surgery and new eye symptoms.

Do not wait for the next scheduled eye‑care appointment—call emergency services or go to the nearest emergency department.

Diagnosis

Evaluation is performed by an ophthalmologist or optometrist with emergency‑care capability. The diagnostic work‑up includes:

1. Clinical Examination

• Slit‑lamp biomicroscopy – assesses corneal edema, pupil size, and angle anatomy.
• Gonioscopy – a special lens that visualizes the drainage angle; confirms angle closure.
• Tonometry – measures intra‑ocular pressure; values often exceed 30 mm Hg (normal 10‑21 mm Hg).

2. Imaging

• Anterior segment optical coherence tomography (AS‑OCT) – non‑invasive imaging that shows angle width.
• Ultrasound biomicroscopy (UBM) – provides high‑resolution images of angle structures when corneal clouding limits view.

3. Additional Tests

• Visual‑field testing (once pressure is controlled) to document any nerve damage.
• Fundus examination to check optic‑nerve head for cupping.

Prompt diagnosis is vital; the eye is usually examined in a darkened room to provoke angle closure and confirm the diagnosis.

Treatment Options

Treatment aims to quickly lower IOP, reopen the drainage angle, and prevent optic‑nerve damage. Management combines emergency medical therapy, laser or surgical procedures, and follow‑up care.

Immediate Medical Therapy (Emergency)

• Topical beta‑blockers (e.g., timolol) – reduce aqueous production.
• Alpha‑agonists (e.g., apraclonidine) – both decrease production and increase outflow.
• Carbonic anhydrase inhibitors (e.g., dorzolamide, oral acetazolamide) – lower fluid formation.
• Hyperosmotic agents (e.g., oral glycerol, IV mannitol) – draw fluid out of the eye, rapidly decreasing pressure.
• Pilocarpine 2 % drops – a miotic that contracts the iris sphincter, pulling the peripheral iris away from the trabecular meshwork.
• These medications are usually given in combination and repeated every 15‑30 minutes until pressure falls below 25 mm Hg.

Definitive Procedures

• Laser peripheral iridotomy (LPI) – a tiny hole is created in the peripheral iris using a laser (YAG or Nd:YAG). The hole provides an alternate pathway for aqueous humor, equalizing pressure between the anterior and posterior chambers. LPI is the first‑line definitive treatment for most patients.
• Laser peripheral iridoplasty – uses an argon laser to contract peripheral iris tissue, widening the angle when a full iridotomy is not feasible.
• Surgical iridectomy – removal of a small iris segment, reserved for cases where laser iridotomy fails or is contraindicated.
• Trabeculectomy or tube shunt surgery – creates a new drainage pathway for chronic cases or after repeated attacks.

Home & Supportive Care

• Maintain a regular follow‑up schedule with an eye specialist (usually every 3‑6 months after an acute episode).
• Avoid medications known to dilate pupils (e.g., over‑the‑counter cold remedies containing antihistamines) unless cleared by your doctor.
• Stay hydrated and avoid excessive caffeine, which can affect IOP.
• Use prescribed eye drops exactly as directed; never stop abruptly without consulting your provider.

Early, aggressive treatment often restores normal pressure and preserves vision. However, some patients may have residual visual field loss despite successful therapy.

Prevention Tips

While not all cases are preventable, risk can be markedly reduced by addressing modifiable factors:

• Screening for narrow angles – Adults over 40, especially hyperopic individuals, should have a gonioscopic exam during routine eye checks.
• Avoid unnecessary pupil‑dilating drugs – Discuss alternatives with your physician if you need antihistamines, anti‑depressants, or anticholinergics.
• Prophylactic laser iridotomy – In eyes identified as high‑risk (very shallow anterior chamber), a preventive LPI can avert an acute attack.
• Manage systemic illnesses – Diabetes, hypertension, and sleep apnea can affect ocular pressure; keep them well‑controlled.
• Protect your eyes from trauma – Wear protective eyewear when playing sports or working with hazardous equipment.
• Limit caffeine and nicotine – Both can cause transient IOP spikes.
• Stay hydrated but avoid fluid overload – Large fluid intake in a short period can increase IOP in susceptible eyes.
• Regular eye exams – At least once every 1–2 years for low‑risk adults; annually for those with known narrow angles or a family history of glaucoma.

Emergency Warning Signs

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References

1. Mayo Clinic. “Acute angle‑closure glaucoma.” Updated 2023. https://www.mayoclinic.org.
2. American Academy of Ophthalmology. “Acute Angle‑Closure Glaucoma.” 2022. https://www.aao.org.
3. National Eye Institute (NEI). “Glaucoma.” 2024. https://www.nei.nih.gov.
4. World Health Organization. “Blindness and Vision Impairment.” 2021. https://www.who.int.
5. Cleveland Clinic. “Acute Angle‑Closure Glaucoma: Symptoms, Diagnosis, Treatment.” 2023. https://my.clevelandclinic.org.