Glaucoma, Primary Closed-Angle

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Basics

Description

Glaucoma is a progressive decline in vision that is usually associated with elevated intraocular pressure (IOP) in the eye, which leads to damage of the optic nerve. Primary angle closure (PAC) is one reason for glaucoma and can be classified as the following:

  • Primary angle-closure suspect (PACS) is >180 degrees of iridotrabecular contact (ITC), normal IOP with no optic nerve damage.
  • PAC is >180 degrees ITC with peripheral anterior synechiae (PAS) or elevated IOP but with no optic neuropathy.
  • Primary angle-closure glaucoma (PACG) is >180-degree ITC with PAS, elevated IOP, and optic neuropathy.
  • Acute angle-closure crisis (AACC) is occluded angle with symptomatic high IOP.
  • Plateau iris configuration is any ITC persisting after a patent laser peripheral iridotomy (LPI) or a plateau iris syndrome which is any ITC persisting after a patent LPI with pressure elevation after dilation.

Geriatric Considerations
Increased risk with age and prior history of cataract, hyperopia, and/or uveitis

Pregnancy Considerations
Medications used may cross the placenta and be excreted into breast milk. Majority of IOP lowering medications are within class C and the risk of adverse effects to the fetus must be balanced with risk of vision loss in the mother.

Epidemiology

  • Older age
  • Female sex
  • More likely in those of Inuit and East or South Asian descent

Prevalence
In 2013, it is estimated to have a worldwide prevalence of 20.2 million people aged 40 to 80 years with majority (15.5 million) in Asia (1). PACG is not as common in the United States; accounts for 10% of all glaucoma

Etiology and Pathophysiology

  • PAC happens when iris touches the trabecular meshwork at the anterior chamber angle. This is called ITC. ITC causes obstruction of aqueous humor outflow through the trabecular meshwork, which causes elevation in IOP. Prolonged ITC can cause scarring, degradation of trabecular meshwork, and loss of vision (1).
  • Most common underlying mechanism of angle closure is pupillary blockage of the aqueous flow from posterior to anterior chamber. This causes increase in pressure in the posterior chamber as compared to the anterior chamber. The buildup of pressure in the posterior chamber leads to anterior bowing of the iris and closing of the angle (1,2).
  • Other mechanisms include predisposing ocular anatomy, such as plateau iris configuration (2).

Genetics
First-degree relatives have a 1–12% increased risk in whites; 6 times greater risk in Chinese patients with positive family history

Risk Factors

  • Age >50 years
  • Female gender
  • Asian or Inuit descent
  • Family history of angle closure
  • Shallow anterior chamber
  • Hyperopia
  • Short axial length
  • Thick crystalline lens
  • Anterior positioned lens
  • Plateau iris
  • Drugs that can induce angle closure:
    • Adrenergic agonists (albuterol, phenylephrine), anticholinergics (oxybutynin, atropine, botulinum toxin A), topiramate, antihistamines, antidepressants including selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs), sulfa-based drugs, cocaine, ecstasy

General Prevention

  • Routine eye exam with gonioscopy for high-risk populations
  • U.S. Preventive Services Task Force: insufficient evidence to recommend for or against screening adults for glaucoma without visual symptoms (3)[A]
  • Prophylactic laser iridotomy may be considered in patients with PACS for preventing PACG.

Commonly Associated Conditions

  • Cataract
  • Hyperopia
  • Microphthalmos
  • Systemic hypertension

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Citation

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TY - ELEC T1 - Glaucoma, Primary Closed-Angle ID - 116897 ED - Baldor,Robert A, ED - Domino,Frank J, ED - Golding,Jeremy, ED - Stephens,Mark B, BT - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116897/all/Glaucoma__Primary_Closed_Angle PB - Wolters Kluwer ET - 27 DB - Medicine Central DP - Unbound Medicine ER -