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What Is Primary Angle-Closure Glaucoma (PACG)?

Primary angle closure glaucoma is a form of glaucoma in which the drainage angle between the iris and cornea becomes blocked without an identifiable secondary cause. The trabecular meshwork is covered by the peripheral iris, which restricts outflow of aqueous humor and raises intraocular pressure. In some people this happens suddenly as an acute angle closure attack with severe pain and blurred vision. In others, closure develops more slowly and causes chronic optic nerve damage. Early detection can protect sight before permanent loss occurs.

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What Is Primary Angle-Closure Glaucoma (PACG)?

Primary angle closure glaucoma is a form of glaucoma in which the drainage angle between the iris and cornea becomes blocked without an identifiable secondary cause. The trabecular meshwork is covered by the peripheral iris, which restricts outflow of aqueous humor and raises intraocular pressure. In some people this happens suddenly as an acute angle closure attack with severe pain and blurred vision. In others, closure develops more slowly and causes chronic optic nerve damage. Early detection can protect sight before permanent loss occurs.

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Anatomy and Mechanism

PACG usually occurs in eyes with crowded anterior segments, such as short axial length, shallow anterior chambers, or thick lenses. Pupil block, in which fluid flow from the posterior to the anterior chamber is impeded at the pupil, pushes the iris forward and narrows the angle. Plateau iris configuration and other anatomic variants can add to narrowing. When the angle closes, the trabecular meshwork is no longer accessible, and pressure rises. Repeated bouts of closure can scar the angle and create lasting damage.

Clinical Features and Risk Factors

Acute attacks cause sudden eye pain, headache, halos around lights, nausea, and vomiting. The eye looks red, the cornea is hazy from edema, and the pupil is mid dilated and sluggish. Chronic forms may be much quieter, with only mild discomfort and gradual vision loss. Risk factors include older age, female sex, hyperopia, Asian or Inuit ancestry, and family history of angle closure. Certain medications that dilate the pupil or cause fluid shifts can precipitate attacks in susceptible eyes.

Diagnosis and Evaluation

Diagnosis relies on gonioscopy, which shows a narrow or closed angle, and on measurement of intraocular pressure and optic nerve status. Indentation gonioscopy helps differentiate appositional closure from permanent synechial closure. Anterior segment optical coherence tomography and ultrasound biomicroscopy can document angle anatomy and lens position. Visual field testing and optic nerve imaging assess the impact on structure and function. Fellow eyes are examined closely because they often share similar anatomy and risk.

Treatment and Long Term Management

Acute attacks require urgent pressure lowering with topical and systemic medications, followed by laser peripheral iridotomy to relieve pupil block. Prophylactic iridotomy is usually offered to the fellow eye. In eyes with persistent angle crowding, lens extraction or lens based procedures can deepen the chamber and widen the angle. Chronic PACG may need ongoing pressure lowering drops, laser trabeculoplasty in selected cases, or glaucoma surgery. Lifelong monitoring is needed, since optic nerve damage from angle closure is permanent once established.

FAQs About Primary Angle-Closure Glaucoma

Is PACG the same as open angle glaucoma?

No, PACG involves a physically narrow or closed angle, while open angle glaucoma has a visible open angle with outflow resistance.

Can primary angle closure glaucoma be prevented?

Identifying narrow angles and performing prophylactic iridotomy in high risk eyes can greatly reduce the chance of acute attacks.

Does a laser iridotomy cure PACG?

It often removes pupil block but some eyes still need drops or surgery to control pressure.

Should family members be screened if I have PACG?

Yes, close relatives benefit from angle and pressure checks because anatomic risk features often run in families.

References

EyeWiki. ?Primary Angle Closure Glaucoma.? https://eyewiki.org/Primary_Angle_Closure_Glaucoma

MSD Manual Professional Version. ?Angle-Closure Glaucoma.? https://www.msdmanuals.com/professional/eye-disorders/glaucoma/angle-closure-glaucoma

National Eye Institute. ?Glaucoma.? https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/glaucoma

NCBI Bookshelf (StatPearls). ?Acute Angle-Closure Glaucoma.? https://www.ncbi.nlm.nih.gov/books/NBK430857/

Mayo Clinic. ?Glaucoma.? https://www.mayoclinic.org/diseases-conditions/glaucoma/symptoms-causes/syc-20372839