Primary Angle-Closure Glaucoma Disease Background

Last updated: 09 March 2026

Introduction

Primary angle-closure disease is a spectrum of progressive changes in the anterior segment of the eye, initially due to trabecular outflow obstruction with synechial or appositional closure of the anterior chamber angle secondary to multiple mechanisms resulting in raised intraocular pressure (IOP) and structural changes in the eyes potentially leading to glaucomatous optic neuropathy. Iridotrabecular contact (ITC) is the hallmark of primary angle-closure disease and the most commonly identified sign wherein the iris appears to touch the anterior chamber angle at the posterior pigmented trabecular meshwork (TM) or more anterior structures and indicates that treatment is required.

Prolonged or repeated ITC leads to functional damage of the TM and the development of peripheral anterior synechiae (PAS). This occurs in either acute or chronic form and may not be associated with elevated IOP or glaucomatous optic neuropathy initially.  

Please see section on Clinical Subtypes.  

Primary angle-closure occurs in anatomically predisposed eye with no identifiable cause (idiopathic); if the cause of angle-closure can be identified, it is said to be secondary.

Epidemiology

Glaucoma is the leading cause of irreversible visual impairment and blindness worldwide.  Primary angle-closure glaucoma is three times more common in Asian population compared to European population. The higher prevalence of angle-closure glaucoma in Asians may be due to shorter axial lengths, possible physiological differences and risk factors. Across the Asian subregion, there was a greater burden of primary angle-closure glaucoma in East Asia.  Women have a higher prevalence of acute-closure glaucoma compared to men. 

Pathophysiology

Mechanisms of Primary Angle-Closure Disease  

The mechanisms responsible for angle closure are defined in terms of the anatomic location of obstruction to aqueous flow. It is important to determine the mechanism involved since initial management is directed at the underlying disease.



Primary Angle-Closure Glaucoma_Disease BackgroundPrimary Angle-Closure Glaucoma_Disease Background




Pupillary Block 

Pupillary block accounts for approximately 75% of cases of primary angle-closure disease and occur more often in patients >50 years old. The aqueous flow from the posterior chamber through the pupil to the anterior chamber is blocked, resulting in the peripheral iris bowing forward and coming into contact with the TM and/or peripheral cornea.  

Obstruction at the Level of the Iris and/or Ciliary Body (“Plateau Iris”)

Plateau iris results from variations in iris and ciliary body anatomy that bring the peripheral iris into contact with the TM. It is characterized by a more anterior iris insertion, a thicker iris and a more anterior ciliary body position. The ciliary processes that are anteriorly positioned cause typical “plateau iris configuration” in which the iris plane is flat and the anterior chamber is not shallow axially. Plateau iris syndrome is plateau iris configuration in the presence of persistent ITC after laser peripheral iridotomy or cataract extraction.  

Other Mechanisms  

Other less frequent mechanisms include lens anomalies (ie thicker, more anteriorly placed lens, aqueous misdirection syndrome occurring posterior to the lens, forward movement of the lens iris diaphragm, resulting in IOP elevation).

Risk Factors

Risk Factors for Primary Angle-Closure Disease  

The demographic risk factors include:

  • Family history of angle closure (increases glaucoma risk 5- to 8-fold; first-degree relatives are at higher risk)
  • Older age
  • Female
  • Asian or Inuit descent

The ocular risk factors include:

  • Hyperopia
  • Shallow central anterior and/or peripheral chamber depth (ACD)
  • Presence of ocular imaging parameters (ie shorter axial length, smaller corneal diameter, reduced angle width, decreased anterior chamber depth, increased lens thickness)

Classification

Classification of Primary Angle-Closure Disease

Primary Angle-Closure Suspect

Primary angle-closure suspect is characterized by ≥180 degrees or ≥2 quadrants of ITC, with normal IOP, absence of PAS, and without evidence of glaucomatous optic neuropathy. Studies showed that patients with untreated primary angle-closure suspect may develop elevated IOP or PAS over 5 years and at risk for primary angle-closure glaucoma and acute angle-closure glaucoma.  

Primary Angle-Closure

Primary angle-closure is defined by at least 180 degrees of ITC together with an elevated IOP and/or PAS, without optic neuropathy. 

Primary Angle-Closure Glaucoma 

Primary angle-closure glaucoma is primary angle-closure with glaucomatous optic neuropathy. Patients may be asymptomatic, presenting for routine eye care, or may present with sudden onset of symptoms and signs of acute angle closure attack. Symptoms may include intermittent or episodic blurring of vision, eye pain, eye redness, frontal headache, glare and halos or colored rings around lights, poor light or dark adaptation, difficulty tracking fast-moving objects, nausea, and vomiting. Primary angle-closure glaucoma causes three times more blindness than primary open-angle glaucoma (POAG). 

Acute Angle-Closure Crisis

Acute angle-closure crisis is the rapid increase of IOP due to sudden obstruction of the chamber angle with complete ITC. This may lead to pressure-induced corneal edema (manifested as blurred vision and, at times, multicolored halos around lights), mid-dilated pupil, vascular congestion, eye pain, and/or headache. An elevated IOP can be accompanied by nausea and vomiting. This may be self-limited and resolve spontaneously or may occur repeatedly. Glaucomatous optic neuropathy can develop if markedly elevated IOP in acute angle-closure crisis is not treated. This may result in permanent loss of vision if left untreated and may affect the other eye.