Acute Angle-Closure Glaucoma
Acute angle-closure glaucoma, often referred to as acute glaucoma, is an ophthalmic emergency caused by sudden obstruction of aqueous humour outflow, leading to a rapid rise in intraocular pressure.
This updated UKMLA guide to acute angle-closure glaucoma is based on RCOphth guidance and NICE CKS, which covers causes, risk factors, symptoms, diagnosis, and management.
Terms and Definitions
| Term / condition | Definition / description |
|---|---|
| Glaucoma | A group of eye diseases that cause progressive optic neuropathy, characterised by visual field defects and optic disc changes
Commonly associated with raised IOP |
| Ocular hypertension | Elevated IOP (> 21 mmHg) but with no signs of glaucoma (i.e. no optic neuropathy / no visual field defect) |
| Normal tension glaucoma | Presence of optic neuropathy (characterised by visual field defects and optic disc changes), but with normal IOP |
| Angle-closure glaucoma (narrow-angle glaucoma) | Glaucoma secondary to narrowing/closure of the iridocorneal angle → impaired aqueous humour drainage → ↑ IOP
Most often presents acutely |
| Open-angle glaucoma | Glaucoma secondary to trabecular meshwork dysfunction, despite an open (normal) iridocorneal angle
Often associated with ↑ IOP Most often presents chronically |
Raised IOP ≠ glaucoma.
Optic nerve neuropathy is needed for it to be glaucoma, indicated by optic disc changes and visual-field defects.
Relevant Anatomy and Physiology
Intra-ocular pressure (IOP)
- IOP helps maintain the shape of the globe
- IOP is mainly determined by the balance between aqueous humour production and aqueous humour drainage
Aqueous humour pathway:
- Produced by the ciliary body (the enzyme carbonic anhydrase plays an important role)
- Flows from the posterior chamber, through the pupil, into the anterior chamber
- Drained out of the eye via the iridocorneal angle → trabecular meshwork → Schlemm’s canal
- A small % is drained via the uveoscleral pathway (via the venous circulation of the iris, ciliary body, choroid, and sclera)
Control of aqueous humour secretion:
- Stimulated by beta-2 receptors
- Decreased by alpha-2 receptors
Causes
Angle-closure glaucoma is most commonly primary (PACG):
- Due to the narrowing of the irido-corneal angle
- Most commonly due to contact/apposition of the peripheral iris and trabecular meshwork (irido-trabecular contact)
- As a result, aqueous humour production continues, but aqueous humour drainage reduces (production > drainage → raised IOP)
Secondary causes (uncommon):
- Lens dislocation / subluxation
- Anterior uveitis (posterior synechiae can block aqueous humour drainage via the pupil, and inflammation can also alter the aqueous drainage)
- Anterior segment neovascularisation (e.g. from retinal vein occlusion)
Risk Factors
Risk factors for PACG:
- Advancing age (as the lens size increases with age → narrowing the iridocorneal angle)
- Females (as they tend to have shallower anterior chambers)
- Asian (prevalence is highest in China)
- Hypermetropia (long-sighted) (long-sighted eyes usually have a shorter axial length, resulting in a shallower anterior chamber and narrower iridocorneal angle)
- Family history
Hypermetropia (long-sighted) → shorter eye axis → associated with angle-closure glaucoma
Myopia (short-sighted) → longer eye axis → associated with open-angle glaucoma
Raised IOP is a major risk factor for primary open-angle glaucoma.
However, in primary angle-closure glaucoma, the key risk factors are anatomical features that narrow the iridocorneal angle; this narrowing then reduces aqueous humour outflow and causes raised IOP. Therefore, in angle-closure glaucoma, raised IOP is better understood as a consequence of angle closure rather than the primary predisposing risk factor.
Diagnosis
Clinical Features
Angle-closure glaucoma often presents as an acute, painful red eye, with associated:
- Headache
- Nausea and vomiting
- Blurred vision + seeing halos around light
Possible examination findings:
- Red, tender, hard eye
- Hazy oedematous cornea
- Semi-dilated / mid-dilated, poorly reactive pupil (classically vertically oval shape)
A history of the following also makes acute angle-closure glaucoma more likely
- Previous episodes of eye pain, blurred vision, headaches, nausea and seeing halos around light (indicate intermittent angle closure episodes that self-resolved)
- Presence of a precipitating factor (any cause of mydriasis), such as:
- Dark room (e.g. watching television)
- Semi-prone position (e.g. reading)
- Use of anticholinergic (e.g. TCA) or adrenergic (e.g. phenylephrine) medications
- Stress or emotional arousal
Angle-closure glaucoma can also be non-acute:
- Intermittent: causes less severe symptoms that often spontaneously resolve, typically on lying supine and closing the eyes, or after sleeping
- Chronic PACG: typically asymptomatic until severe visual field defects affect vision
~10% of the UK blindness registrations are due to glaucoma.
Globally, glaucoma is the leading cause of irreversible blindness, and the 2nd most common cause of blindness (after cataracts)
Investigation and Diagnosis
Acute angle-closure glaucoma is an ophthalmological emergency → admit to ophthalmology immediately for assessment and treatment.
Diagnostic work-up for suspected acute primary angle-closure glaucoma (in secondary care):
| Investigation / test | Interpretation / description |
|---|---|
| Slit lamp examination | Definitive investigation: gonioscopy
Measure the anterior chamber depth
|
| IOP measurement | Methods:
Finding in acute-closure glaucoma: ↑ (>21 mmHg) |
Anterior segment OCT can be used as a supplementary test alongside gonioscopy. Importantly, it does NOT replace the need for gonioscopy.
It can image and measure the iridocorneal angle, therefore it can be used as a triage test in community or primary care settings to exclude the need for gonioscopy.
To diagnose acute primary angle-closure glaucoma, ALL the following must be met:
- Presence of angle-closure (demonstrated on gonioscopy)
- ↑ IOP
- Secondary causes excluded (by measuring the anterior chamber depth)
Management
This section covers acute primary angle-closure glaucoma, rather than other forms of angle-closure glaucoma.
This is the most important type to recognise in exams at a non-specialist level, as it is an ophthalmic emergency requiring urgent assessment and treatment.
Primary Care Management
If acute angle-closure glaucoma is suspected → refer immediately to be admitted under ophthalmology
If immediate admission is not possible → start emergency treatment in primary care:
- Lie patient flat with face up, do NOT support the head with a pillow
- Pharmacological management
- Analgesia and antiemetic as needed
- IOP-lowering agents:
- Pilocarpine eye drops
- Acetazolamide oral 500 mg
Secondary Care Management
Initial stat medications (to be given once the diagnosis is confirmed):
- Dorzolamide 2% + timolol 0.5% combined eye drops
- Apraclonidine 0.5% eye drops
- Pilocarpine 2% (defer if IOP >40 mmHg – withhold until IOP is <40 mmHg)
- IV acetazolamide 250 mg (if IOP >40 mmHg)
Further management:
| 1st line definitive management | Laser peripheral iridotomy
If laser iridotomy is not technically possible, consider a surgical iridectomy |
| Other interventions | If the initial stat medications failed to reduce IOP / relieve symptoms / cornea remains too oedematous to perform laser peripheral iridotomy, consider:
If the patient has a concurrent cataract with acute primary angle-closure glaucoma:
|
Do not perform the following:
- Emergency trabeculectomy
- Limbal paracentesis