EM@3AM: Acute Angle Closure Glaucoma

Answer: Acute angle closure glaucoma secondary to anterior uveitis (i.e. uveitic glaucoma)

Background:

• Acute angle-closure glaucoma (AACG) is an ophthalmologic emergency characterized by a rapid increase in intraocular pressure (IOP) due to impaired outflow of aqueous humor
• In the healthy eye, aqueous humor from the ciliary body freely flows over the lens of the eye, through the pupil, and into the anterior chamber where it is drained through the trabecular network and uveoscleral system (Figure 3)
• Patients with open-angle glaucoma have elevated IOP but a normal anterior chamber angle¹
• In AACG, normal functioning outflow tracts are obstructed by the iris abutting the cornea or trabecular network²

Etiology:

• Primary AACG occurs in the absence of cause or associated disease
  • A shallow anterior chamber or narrow-angle predisposing to sudden angle closure^1,3
• Secondary AACG occurs as a consequence of an underlying cause or disease
  • Trauma, tumors, inflammatory conditions (i.e., uveitis)²
• Secondary AACG can result from several mechanisms in the uveitic eye:
  • Pupillary block can occur when circumferential synechiae form on the posterior aspect of the iris blocking humoral flow from posterior to anterior chamber. Fluid buildup causes iris bombé, or bowing of the iris, which closes the angle between the iris and cornea
  • Pupillary block may also occur from peripheral synechiae form on the anterior surface of the iris, drawing the iris and cornea closer together and closing the angle
  • Less commonly, inflammation in the ciliary body may displace it anteriorly, closing the angle in the absence of pupillary block⁴

Epidemiology:  

• Glaucoma is the primary cause of irreversible blindness worldwide⁵
• AACG is much less common than open-angle glaucoma, representing about 1/3 of glaucoma cases⁶
  • Women are 3 times as likely to be affected as men^7,8
  • The extremes of age are most susceptible, (<6yo, >60yo)⁸
  • Other risk factors include chronic ocular steroid use, Asian descent, pupillary dilating medications (TCAs, anticholinergic, antiparkinsonian drugs), hyperopia, recent eye surgery, family history of glaucoma³
• Ocular inflammatory conditions can predispose patients to the development of glaucoma
  • 20% of patients with glaucoma develop this condition from ocular infection⁹
  • Uveitis is the leading inflammatory cause of glaucoma^10–12
    • 10-20% of patients with uveitis develop glaucoma, with prevalence directly proportional to the time since diagnosis (6.5%, 11.1%, 22.7% at one, five, and ten years, respectively)^3,4

Clinical Presentation:

• AACG most commonly manifests itself with pain radiating from the eye, visual impairment, conjunctival hyperemia, and nausea and vomiting with a tense, rock-hard globe¹
• Corneal edema (i.e. a “hazy” cornea” and a mid-dilated, minimally-reactive pupil may also be seen¹⁴
• May present with isolated headache (frontal/periorbital) and visual complaints such as blurred vision (even in the absence of a red eye)¹⁵
• Other systemic symptoms may include abdominal cramping, nausea, and vomiting¹⁶

Evaluation:

• Pupillary exam
• Visual acuity
• Visual fields
• Extraocular movements
• Evaluation of IOP
• Fluorescein exam to rule out abrasions or other causes of scleral/conjunctival injection (UV keratitis, HSV keratitis, etc.)
• Slit-lamp examination, which is especially important at sites where ophthalmology is not readily available
  • May show flare and cells, swollen optic nerve, shallow anterior chamber, bombe, synechiae⁸

Diagnosis:

• AACG is largely a clinical diagnosis with suggestive clinical exam findings and elevated IOP (>21 mmHg)¹⁷
• Two of the following: acute ocular pain, nausea and vomiting, intermittent blurry vision with haloes around lights, photophobia, vision loss plus
  • Three of the following, IOP > 21 (usually > 40), corneal epithelial edema, conjunctival injection, fixed mid-dilated pupil, shallow anterior chamber
• Initial evidence of glaucomatous change in the eye can be appreciated via fundoscopic exam showing tissue loss at the neuroretinal rim, optic nerve cupping, or hemorrhages at the edge of the optic disc¹
• Further ophthalmologic evaluation with optical coherence tomography (OCT) is needed to evaluate for glaucomatous changes⁸

Treatment:

• Consult ophthalmology
• Elevate the head of the bed >30 degrees
• Medications to decrease IOP:^1,18
  • Decrease production of aqueous humor:
    • Beta blockade: timolol 0.5% gtt one drop BID OR Betaxolol 0.5% gtt, one drop TID
      • Can cause bradycardia, hypotension, and bronchospasm¹⁹
    • Alpha-2 agonists: Apraclonidine 1% gtt, one drop TID OR brimonidine 0.2% gtt, one drop TID
      • Does NOT have systemic cardiac effects¹⁹
    • Carbonic anhydrase inhibitors: Acetazolamide 500 mg PO or IV, then 250 mg 4 hours later OR Brinzolamide 0.5% gtt, one drop TID OR Dorzolamide 2% gtt, one drop TID
      • Contraindications to carbonic anhydrase inhibitors include sickle cell disease and sulfa allergies^19,20
    • Decrease the volume of aqueous humor:
      • Osmotic diuretic: mannitol 15% or 20% solution 1.5-2 g/kg IV over 30 minutes
    • Improve the outflow of aqueous humor
      • Pilocarpine 1-2 drops every 15 minutes for 2 doses
        • Though cholinergic agents are often used to improve the outflow of aqueous humor in typical cases of AACG, they should NOT be used in uveitic glaucoma – they can make the condition worse⁸
•  Treat the underlying cause
  • Ophthalmology may recommend antivirals or anti-inflammatory/immunosuppressive agents depending upon the cause⁸
• Patients may need definitive therapy with laser peripheral iridotomy, trabeculectomy, or various other surgical procedures⁸

Prognosis:

• Primary AACG has good prognosis if treated early²¹
• The prognosis of secondary AACG varies depending on the underlying etiology
  • In uveitic glaucoma, visual outcomes vary based on the underlying cause with mixed etiologies leading to the worst outcomes and autoimmune the best
    • Other causes include infectious or autoinflammatory²³

Pearls:

• AACG presents with a painful red eye, visual complaints, sometimes with gastrointestinal symptoms
• IOP measurement is essential for patients with suspected AACG
• Emergent treatment involves decreasing aqueous humor production, decreasing its volume, and promoting increased outflow, and ophthalmology consult
  • Cholinergic agents should be avoided in the uveitic eye with AACG as they can make uveitic glaucoma worse