Acute Angle-Closure Glaucoma

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Acute angle-closure glaucoma (AACG) is an acute rise in intraocular pressure associated with narrowing of the anterior chamber angle of the eye (the angle between the iris and cornea) causing optic nerve damage.

The incidence of AACG in the United Kingdom is approximately 2 cases per 100,000 people per year.1

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The aqueous humour supplies nutrients to the cornea and lens. It is produced by the ciliary body and travels through the pupil into the anterior chamber (the area between the iris and cornea).

Aqueous humour drains out of the anterior chamber through the trabecular meshwork and flows into the canal of Schlemm (Figure 1).

Figure 1. Aqueous humour anatomy.2


In AACG, there is reduced drainage of aqueous humour due to anterior chamber angle narrowing.

This causes a rapid rise in intraocular pressure and subsequent optic nerve damage.

A common cause of anterior chamber angle closure is pupillary block, which occurs when aqueous humour outflow is obstructed due to contact between the iris and lens.

Risk factors

Risk factors for AACG include:

  • Increasing age: particularly 6th to 7th decade of life
  • Female sex: women have a four times greater risk than men
  • Asian ethnicity
  • Family history
  • Anatomical predisposition: including short eyeball length and hypermetropia (long-sightedness)

Pupil mid-dilation can cause AACG by precipitating pupillary block in those at risk.

Pupil mid-dilation can be caused by being in a dark room or the use of certain medications such as anticholinergics (e.g. oxybutynin) or pupil-dilating drops (e.g. atropine).

Clinical features

AACG is an important differential diagnosis to consider in any patient presenting with a painful red eye.


AACG symptoms tend to develop over hours to days. Since pupil mid-dilation can trigger AACG, the patient may have been in a dark room when symptoms began or may be taking medications that cause pupil dilation.

Typical symptoms of AACG include:

  • Headache
  • Nausea and vomiting
  • Visual changes such as blurred vision and halos around lights

Other important areas to cover in the history include:

  • Medication history: drugs that can cause pupillary dilation

Clinical examination

As a result of the rapid rise in intraocular pressure, the eye appears red and is hard to touch.

Raised intraocular pressure also causes corneal oedema giving the cornea a hazy appearance (Figure 2). The pupil is often fixed in a mid-dilated position and does not react to light.

Typical clinical findings in AACG include:

  • Unilateral red eye
  • Fixed mid-dilated pupil
  • Corneal haze due to oedema in the cornea
  • The eyeball is hard to touch


An example of acute angle-closure glaucoma
Figure 2. An example of acute angle-closure glaucoma showing a mid-dilated pupil and corneal haze.3

Differential diagnoses

Differential diagnoses to consider in patients presenting with a red painful eye include:

  • Conjunctivitis
  • Anterior uveitis
  • Scleritis
  • Episcleritis


Relevant investigations for AACG include gonioscopy and tonometry.

Gonioscopy is the gold standard investigation for assessing the angle between the iris and cornea (Figure 3). If AACG is suspected, patients should be immediately sent for gonioscopy.

Figure 3. A diagram showing how gonioscopy works.4

Tonometry is used to measure intraocular pressure. In AACG, intraocular pressure is typically >30mmHg.

The most widely used type of tonometry in AACG is Goldmann applanation tonometry, which calculates intraocular pressure by assessing the force required to flatten a fixed area of the cornea.


AACG is sight-threatening and requires an emergency referral to ophthalmology.

Initially, medical management is used to reduce intraocular pressure. Surgical intervention can later be used to lower intraocular pressure and prevent reoccurrences.

Patients with AACG should avoid dark rooms and eye patches as this may worsen angle closure by causing mid-dilation of the pupils. Symptomatic relief can be achieved with analgesia and anti-emetics.

Medical management

A triad of medications are commonly used to reduce intraocular pressure:

  • Topical timolol: a beta-blocker to decrease aqueous humour production
  • Topical pilocarpine: a miotic that constricts the pupil and increases aqueous humour outflow
  • Oral or intravenous acetazolamide: a carbonic anhydrase inhibitor to decrease aqueous humour production

Surgical management

Once intra-ocular pressure is controlled, bilateral peripheral iridotomy (making a hole in the iris using a laser) may be used to improve aqueous humour outflow.

Peripheral iridotomy is performed on both eyes to reduce the risk of AACG reoccurrence in the other eye.


Complications of AACG include:

  • Sight loss
  • Central retinal artery or vein occlusion
  • Repeated episodes of AACG

Key points

  • Acute angle-closure glaucoma (AACG) is an acute rise in intraocular pressure associated with narrowing of the anterior chamber angle of the eye.
  • AACG is sight-threatening and should be considered in any patient presenting with a red painful eye. 
  • Risk factors include increasing age, Asian ethnicity, female sex and hypermetropia.
  • AACG can be precipitated by inducing pupil mid-dilation from being in a dark room or the use of certain medications.
  • Typical symptoms include headache, nausea and vomiting and visual changes (e.g. blurred vision or halos around lights).
  • Typical clinical findings include a red-eye associated with a fixed mid-dilated pupil and corneal haze.
  • Immediate referral to ophthalmology and early initiation of intraocular pressure-lowering treatment is key for preventing sight loss.
  • Medical management involves topical timolol, topical pilocarpine and oral/intravenous acetazolamide. Surgical management involves bilateral peripheral iridotomy to improve aqueous humour outflow. 
  • Complications include sight loss, central retain artery or vein occlusion and recurrence of AACG. 


General Practitioner


Dr Chris Jefferies


  1. Royal College of Ophthalmologists. The Management Of Angle-Closure Glaucoma. Available from: [LINK]
  2. Holly Fischer (modified by Jonathan Malcolm). Three Main Layers of the Eye. License: [CC BY]. Available from: [LINK]
  3. Jonathan Trobe. Acute Angle Closure-glaucoma. License: [CC BY]. Available from: [LINK].
  4. Mick Lucas. Gonioscopy. License: [CC BY]. Available from: [LINK].
  5. Baldwin A, Hjeld N, Goumalatsou C, Myers G. Oxford Handbook of Clinical Specialties. 10th ed. Book published in 2016.
  6. Lowth M. Acute-closure glaucoma. Published in 2015. Available from: [LINK]
  7. The College of Optometrists. Primary Angle Closure / Primary Angle Closure Glaucoma (PAC / PACG). Published in 2018. Available from: [LINK]
  8. Giaconi JA, Lim A. Primary vs. Secondary Angle Closure Glaucoma. Published in 2020. Available from: [LINK]


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