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. Angle-closure is a mechanical blockage of the trabecular meshwork (TM) by the peripheral iris.
  • In primary angle-closure (PAC), there is an anatomical predisposition with no identifiable secondary pathologic condition.
  • In secondary angle-closure, there is an identifiable pathologic cause, such as iris neovascularization or an enlarged cataractous lens.
  • Angle-closure can be classified as the following:
    • Primary angle-closure suspect (PACS) is >180 degrees of iridotrabecular contact (ITC), but no evidence of TM or optic nerve damage.
    • PAC is >180 degrees of ITC with peripheral anterior synechiae (PAS) or elevated IOP but with no optic neuropathy.
    • Primary angle-closure glaucoma (PACG) is PAC with glaucomatous optic neuropathy.
    • Acute angle-closure crisis (AACC) is when the angle is occluded with symptomatic high IOP. It is a medical emergency requiring prompt treatment.

Geriatric Considerations
Increased risk with age with history of hyperopia and cataracts.

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. PAC is 2 to 4 times more common in women than in men. Women tend to have smaller anterior segments and shorter axial lengths.
  • More likely in those of Inuit and East or South Asian descent

Prevalence
The prevalence of PACG in patients older than 40 years varies depending on race and ethnicity. The prevalence is 0.1%–0.2% in blacks, 0.1%–0.6% in whites, 0.3% in the Japanese, 0.4%–1.4% in other East Asians, 2.1%–5.0% in the Inuit. The burden of PACG is greater in Asian countries.

Etiology and Pathophysiology

  • PAC happens when iris touches the trabecular meshwork in the anterior chamber angle. ITC causes obstruction of aqueous humor outflow through the trabecular meshwork, which causes elevation in IOP. Prolonged ITC can cause scarring, with formation of PAS.
  • 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.
    • One of the most important factors in closing the angle in an anatomically predisposed eye is dilation of the pupil. Dilation leading to closure of the angle may occur as a result of a variety of causes including darkness, emotion, and medications that can cause the pupil to dilate. Pupillary block is maximal when the pupil is in the mid-dilated position.
  • Plateau iris syndrome is an atypical configuration of the anterior chamber angle that can result in acute or chronic PAC. Angle-closure in plateau iris is most often caused by anteriorly positioned ciliary processes that narrow the anterior chamber recess by pushing the peripheral iris forward. A component of pupillary block is often present.

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 by dilating the pupil include:
    • Adrenergic agonists (albuterol, phenylephrine), anticholinergics (oxybutynin, atropine), antihistamines, antidepressants including selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs), and cocaine
  • Drugs that can induce angle-closure by causing a uveal effusion include:
    • Topiramate and other sulfonamides

General Prevention

  • Routine eye exam with gonioscopy for high-risk populations
  • Prophylactic laser iridotomy may be considered in patients with PACS for preventing PACG.

Commonly Associated Conditions

  • Cataract
  • Hyperopia

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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. Angle-closure is a mechanical blockage of the trabecular meshwork (TM) by the peripheral iris.
  • In primary angle-closure (PAC), there is an anatomical predisposition with no identifiable secondary pathologic condition.
  • In secondary angle-closure, there is an identifiable pathologic cause, such as iris neovascularization or an enlarged cataractous lens.
  • Angle-closure can be classified as the following:
    • Primary angle-closure suspect (PACS) is >180 degrees of iridotrabecular contact (ITC), but no evidence of TM or optic nerve damage.
    • PAC is >180 degrees of ITC with peripheral anterior synechiae (PAS) or elevated IOP but with no optic neuropathy.
    • Primary angle-closure glaucoma (PACG) is PAC with glaucomatous optic neuropathy.
    • Acute angle-closure crisis (AACC) is when the angle is occluded with symptomatic high IOP. It is a medical emergency requiring prompt treatment.

Geriatric Considerations
Increased risk with age with history of hyperopia and cataracts.

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. PAC is 2 to 4 times more common in women than in men. Women tend to have smaller anterior segments and shorter axial lengths.
  • More likely in those of Inuit and East or South Asian descent

Prevalence
The prevalence of PACG in patients older than 40 years varies depending on race and ethnicity. The prevalence is 0.1%–0.2% in blacks, 0.1%–0.6% in whites, 0.3% in the Japanese, 0.4%–1.4% in other East Asians, 2.1%–5.0% in the Inuit. The burden of PACG is greater in Asian countries.

Etiology and Pathophysiology

  • PAC happens when iris touches the trabecular meshwork in the anterior chamber angle. ITC causes obstruction of aqueous humor outflow through the trabecular meshwork, which causes elevation in IOP. Prolonged ITC can cause scarring, with formation of PAS.
  • 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.
    • One of the most important factors in closing the angle in an anatomically predisposed eye is dilation of the pupil. Dilation leading to closure of the angle may occur as a result of a variety of causes including darkness, emotion, and medications that can cause the pupil to dilate. Pupillary block is maximal when the pupil is in the mid-dilated position.
  • Plateau iris syndrome is an atypical configuration of the anterior chamber angle that can result in acute or chronic PAC. Angle-closure in plateau iris is most often caused by anteriorly positioned ciliary processes that narrow the anterior chamber recess by pushing the peripheral iris forward. A component of pupillary block is often present.

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 by dilating the pupil include:
    • Adrenergic agonists (albuterol, phenylephrine), anticholinergics (oxybutynin, atropine), antihistamines, antidepressants including selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs), and cocaine
  • Drugs that can induce angle-closure by causing a uveal effusion include:
    • Topiramate and other sulfonamides

General Prevention

  • Routine eye exam with gonioscopy for high-risk populations
  • Prophylactic laser iridotomy may be considered in patients with PACS for preventing PACG.

Commonly Associated Conditions

  • Cataract
  • Hyperopia

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