closed-angle glaucoma
Summary
Closed-angle (angle-closure) glaucoma occurs when the iris bulges forward and obstructs the trabecular meshwork/anterior chamber angle, blocking aqueous humor outflow and causing a rapid rise in intraocular pressure (IOP). It presents as an ophthalmic emergency with severe eye pain, headache, nausea/vomiting, blurred vision, and halos around lights, with a fixed mid-dilated pupil and red eye. It contrasts with open-angle glaucoma, which is typically chronic and painless.
Detail
Pathophysiology: Acute angle-closure glaucoma results from anatomical predisposition (shallow anterior chamber, hyperopia) leading to pupillary block—the iris and lens come into apposition, preventing aqueous flow from the posterior to anterior chamber. This causes posterior chamber pressure to push the peripheral iris forward, closing the angle and obstructing the trabecular meshwork. IOP can rise rapidly (>40-80 mmHg), causing optic nerve damage and vision loss if untreated.
Risk factors: Asian and Inuit ethnicity, female sex, older age, hyperopia (farsightedness, shorter axial length), family history, and shallow anterior chamber. Precipitating factors include pupillary dilation—dim lighting, anticholinergic medications (e.g., antihistamines, TCAs), sympathomimetics, and emotional stress.
Clinical presentation: Sudden onset of severe unilateral eye pain, headache, blurred vision, halos around lights (due to corneal edema), nausea and vomiting (can mimic acute abdomen). Exam reveals a red eye, steamy/cloudy cornea, fixed and mid-dilated pupil, and firm globe on palpation. IOP is markedly elevated.
Diagnosis: Tonometry showing elevated IOP; gonioscopy demonstrating a closed anterior chamber angle; slit lamp exam.
Management: This is an ophthalmologic emergency. Initial medical therapy includes topical beta-blockers (timolol), alpha-2 agonists (apraclonidine), topical/systemic carbonic anhydrase inhibitors (acetazolamide), and hyperosmotic agents (mannitol) to rapidly lower IOP. Pilocarpine (miotic) is used once IOP is reduced to open the angle by constricting the pupil and pulling the iris away from the trabecular meshwork. Definitive treatment is laser peripheral iridotomy, which creates an opening in the iris to relieve pupillary block; often performed prophylactically on the fellow eye. Avoid mydriatics.
Complications if untreated: permanent vision loss due to optic nerve damage from sustained elevated IOP, potentially within hours.
Distinguish from open-angle glaucoma: Open-angle is chronic, often asymptomatic until advanced, with normal-appearing angle on gonioscopy; progressive optic nerve cupping and peripheral vision loss due to trabecular meshwork dysfunction.
Sources
- First Aid for the USMLE Step 1
- Vaughan & Asbury's General Ophthalmology
- UpToDate: Angle-closure glaucoma
- Kaplan USMLE Step 1 Lecture Notes: Ophthalmology
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.