Acute Angle-Closure Glaucoma Flashcards
What is acute angle-closure glaucoma?
Acute angle-closure glaucoma (ACG) is a group of diseases in which there is reversible (appositional) or adhesional (synechial) closure of the anterior-chamber angle resulting in elevation of the intra-ocular pressure (IOP). T
Briefly describe the pathophysiology of acute angle-closure glaucoma
Acute angle-closure glaucoma occurs when the iris bulges forward and seals off the trabecular meshwork from the anterior chamber preventing aqueous humour from being able to drain away. This leads to a continual build-up of pressure in the eye. The pressure builds up particularly in the posterior chamber, which causes pressure behind the iris and worsens the closure of the angle.
What are the risk factors for acute angle-closure glaucoma?
- Increasing age
- Females
- x4 times more often than males
- Family history
- Chinese and East Asian ethnic origin
- Unlike open-angle glaucoma, it is rare in people of black ethnic origin
- Shallow anterior chamber
- Use of medications that induce angle narrowing
What medications can precipitate acute angle-closure glaucoma?
Certain medications can precipitate acute angle-closure glaucoma:
- Adrenergic medications such as noradrenalin
- Anticholinergic medications such as oxybutynin and solifenacin
- Tricyclic antidepressants such as amitriptyline, which have anticholinergic effects
What are the clinical features of acute angle-closure glaucoma?
The patient will generally appear unwell in themselves. They have a short history of:
- Severely painful red eye
- Blurred vision
- Halos around lights
- Associated headache, nausea and vomiting
What are the signs of acute angle-closure glaucoma on examination?
- Red-eye
- Teary
- Hazy cornea
- Decreased visual acuity
- Dilatation of the affected pupil
- Fixed pupil size
- Firm eyeball on palpation
What investigations should be ordered for acute angle-closure glaucoma?
- Gonioscopy, examination of anterior chamber angle
- Slit-lamp examination
- Automatic static perimetry
Briefly describe the treatment of acute angle-closure glaucoma
Patients with potentially life-threatening causes of red eye should be referred for same-day assessment by an ophthalmologist. If there is a delay in admission, whilst waiting for an ambulance:
- Lie patient on their back without a pillow
- Give pilocarpine eye drops (2% for blue, 4% for brown eyes)
- Give acetazolamide 500 mg orally
- Given analgesia and an antiemetic if required
Pilocarpine and acetazolamide are used to treat acute angle-closure glaucoma.
What is the mechanism of action of pilocarpine?
Pilocarpine acts on the muscarinic receptors in the sphincter muscles in the iris and causes constriction of the pupil. Therefore it is a miotic agent. It also causes ciliary muscle contraction. These two effects cause the pathway for the flow of aqueous humour from the ciliary body, around the iris and into the trabecular meshwork to open up.
What is the mechanism of action of acetazolamide?
Acetazolamide is a carbonic anhydrase inhibitor. This reduces the production of aqueous humour.
Briefly describe the secondary care management of acute angle-closure glaucoma
Various medical options can be tried to reduce the pressure:
- Pilocarpine
- Acetazolamide (oral or IV)
- Hyperosmotic agents such as glycerol or mannitol increase the osmotic gradient between the blood and the fluid in the eye
- Timolol is a beta-blocker that reduces the production of aqueous humour
- Dorzolamide is a carbonic anhydrase inhibitor that reduces the production of aqueous humour
- Brimonidine is a sympathomimetic that reduces the production of aqueous fluid and increase uveoscleral outflow
What is the definitive treatment of acute angle-closure glaucoma?
Laser iridotomy is usually required as a definitive treatment. This involves using a laser to make a hole in the iris to allow the aqueous humour to flow from the posterior chamber into the anterior chamber. The relieves pressure that was pushing the iris against the cornea and allows the humour the drain.
What are the complications of acute angle-closure glaucoma?
- Fellow eye attack
- Renal vein occulsion
- Loss of vision
- Permanent decrease in visual acuity
What differentials should be considered for acute angle-closure glaucoma?
- Open-angle glaucoma (primary and secondary)
- Other optic neuropathies
- Eye trauma
- Keratitis
- Conjunctivitis
- Corneal ulcer
