Primary Angle Closure
Definition
A spectrum of conditions characterized by apposition or adhesion of the peripheral iris to the trabecular meshwork, resulting in impaired aqueous outflow; includes primary angle closure suspect, primary angle closure, and primary angle closure glaucoma.
Clinical Snapshot
Primary angle closure (PAC) encompasses a spectrum from primary angle closure suspect (PACS — narrow angle without IOP elevation or optic nerve damage) through primary angle closure (PAC — elevated IOP or peripheral anterior synechiae) to primary angle closure glaucoma (PACG — with glaucomatous optic nerve damage). Acute angle closure crisis — sudden, severe IOP elevation from complete angle closure — is an ophthalmic emergency. Chronic angle closure is frequently asymptomatic and underdiagnosed.
Epidemiology
PACG affects approximately 20 million people worldwide and is responsible for approximately 50% of glaucoma blindness globally, despite representing only 25% of glaucoma cases. It is significantly more prevalent in Asian populations (particularly East and South Asian) and in hyperopic individuals.
Pathophysiology
The primary mechanism is pupillary block — aqueous humor cannot flow freely from the posterior to anterior chamber through the pupil, creating a pressure differential that bows the peripheral iris anteriorly (iris bombé), closing the angle. Plateau iris configuration (anteriorly positioned ciliary processes) is a secondary mechanism. Angle closure obstructs aqueous outflow through the trabecular meshwork, causing IOP elevation.
Risk Factors
- Hyperopia (short axial length, shallow anterior chamber)
- Asian ancestry (particularly East and South Asian)
- Female sex
- Advanced age (lens thickening narrows the angle)
- Family history of angle closure
- Shallow anterior chamber depth
Clinical Presentation
Acute angle closure crisis: sudden severe ocular pain, headache, nausea/vomiting, blurred vision with halos around lights, conjunctival injection, corneal edema, mid-dilated fixed pupil, and markedly elevated IOP (often > 40–50 mmHg). Chronic angle closure: asymptomatic or mild intermittent symptoms; detected on gonioscopy. Subacute angle closure: episodic symptoms that resolve spontaneously.
Diagnostic Pearls
- Gonioscopy is the gold standard for angle assessment — it cannot be replaced by slit lamp estimation alone.
- Acute angle closure crisis is a clinical diagnosis — do not delay treatment for confirmatory testing.
- The fellow eye in acute angle closure has a narrow angle in the vast majority of cases — prophylactic laser iridotomy is indicated.
- Plateau iris should be suspected when angle closure recurs after patent iridotomy — ultrasound biomicroscopy (UBM) confirms the diagnosis.
Differential Diagnosis
- Secondary angle closure (neovascular, inflammatory, lens-induced)
- Acute iritis (pain, photophobia, but IOP usually normal or low)
- Cluster headache (periorbital pain without ocular signs)
- Corneal hydrops (pain, vision loss, but different mechanism)
Evidence-Based Management
Acute angle closure crisis: immediate IOP reduction with topical beta-blockers, alpha-agonists, carbonic anhydrase inhibitors, and systemic acetazolamide; IV mannitol if needed; pilocarpine to constrict the pupil and open the angle; laser peripheral iridotomy (LPI) once the cornea clears. Prophylactic LPI for the fellow eye. Chronic PAC/PACG: LPI is first-line; lens extraction (cataract surgery) is increasingly recognized as definitive treatment for angle closure driven by lens-related mechanisms.
Monitoring & Follow-Up
Post-LPI: confirm iridotomy patency and angle opening on gonioscopy. Monitor IOP, optic nerve, and visual fields as for POAG in PACG patients.
Clinical Pearls
- Acute angle closure is an emergency — every minute of elevated IOP causes irreversible optic nerve damage.
- The fellow eye requires prophylactic LPI — the risk of acute closure in the fellow eye is approximately 50% over 5 years without treatment.
- Lens extraction is increasingly recognized as definitive treatment for angle closure — the EAGLE trial demonstrated superiority of clear lens extraction over LPI for PAC and PACG.
- Plateau iris requires iridoplasty or lens extraction — LPI alone is insufficient.
Related Therapeutics — Clinician's Companion
- Glaucoma Therapeutics — Prostaglandins, Beta-blockers, CAIs (Clinician's Companion)
- Oral Therapeutics — Acetazolamide (Clinician's Companion)
Key References
- 1.Aung T, et al. Primary angle-closure glaucoma. Lancet. 2015.
- 2.Azuara-Blanco A, et al. Effectiveness of early lens extraction for the treatment of primary angle-closure glaucoma (EAGLE). Lancet. 2016.
This entry is an educational reference designed to support clinical reasoning and awareness. It does not constitute medical advice, establish a standard of care, or replace individualized patient assessment. Clinicians should consult current guidelines and applicable clinical resources when making patient care decisions.