Primary Angle-Closure Glaucoma

Overview

Primary angle-closure glaucoma is defined as a glaucomatous optic neuropathy with associated characteristic enlargement of optic disc cupping and visual field loss that is secondary to ocular hypertension caused by closure of the drainage angle.¹ The fundamental pathologic process involves appositional approximation or contact between the iris and trabecular meshwork, which obstructs aqueous humor drainage.^1,3 This condition is potentially devastating and represents a common cause of blindness worldwide, accounting for approximately half of all glaucoma-related blindness.^3,5 The disease spectrum encompasses primary angle closure suspects, primary angle closure with evidence of chronic angle damage, and established PACG with glaucomatous optic neuropathy.²

Epidemiology & Risk Factors

Primary angle-closure glaucoma demonstrates distinct demographic patterns. The risk is highest among women, the elderly, and hyperopic individuals.³ The condition is most prevalent in Asia, where it represents a major public health concern.³ Anatomical predispositions include shallow anterior chambers, anteriorly positioned or anteriorly pushed lenses, and angle crowding.³ Recent genome-wide association studies have identified eight new susceptibility loci for primary angle closure, and both PACG and primary open-angle glaucoma have been found to share partly overlapping genetic features.⁴

Pathophysiology

Angle closure results from appositional approximation or adhesive contact between the iris and trabecular meshwork, obstructing aqueous outflow and elevating IOP.^1,3 Multiple mechanisms contribute to angle closure beyond classic pupillary block and plateau iris. These include increased choroidal thickness, uveal expansion, and other anatomical factors that may be responsible for presenting features of PACG.⁵ Eyes predisposed to angle closure typically have shallow anterior chambers, anteriorly positioned lenses, and crowded angle configurations.³ The elevated IOP ultimately leads to progressive optic nerve degeneration when untreated.¹ Emerging research suggests that sympathetic-parasympathetic nerve activity balance and psychological status may also play roles in disease mechanisms.⁵

Clinical Presentation

The clinical presentation of PACG varies across the disease spectrum. Some patients may be asymptomatic primary angle closure suspects identified during routine examination. Others present with chronic symptoms related to intermittent angle closure or elevated IOP. Acute angle closure crisis represents a medical emergency with sudden onset of severe ocular pain, blurred vision, halos around lights, nausea, and vomiting. Chronic angle closure may present with gradual visual field loss and optic nerve damage detected during comprehensive examination. The signs of chronic angle damage and glaucomatous optic neuropathy guide treatment decisions.²

Exam Findings

Key examination findings include:

• Shallow anterior chamber depth on slit-lamp examination
• Narrow or closed angle structures on gonioscopy
• Elevated intraocular pressure (when angle closure is present)
• Glaucomatous optic disc changes with characteristic cupping
• Visual field defects corresponding to optic nerve damage
• Appositional contact or synechial adhesions between iris and trabecular meshwork on gonioscopy^1,3

Gonioscopy is the cornerstone diagnostic technique for evaluating angle anatomy and detecting closure.³ Anterior segment optical coherence tomography and ultrasound biomicroscopy can aid in diagnosis and assessment of angle structures.³

Classification

Current classification systems for PACG remain controversial.⁵ The disease spectrum typically includes primary angle closure suspects (anatomically narrow angles without other signs), primary angle closure (evidence of trabecular meshwork obstruction with elevated IOP or peripheral anterior synechiae but without glaucomatous optic neuropathy), and primary angle-closure glaucoma (angle closure with glaucomatous optic disc damage and visual field loss).² Classification may also consider the mechanism of closure, such as pupillary block-related closure versus non-pupillary block mechanisms including plateau iris syndrome.³ Serial gonioscopy helps track progression from one category to another.²

Differential Diagnosis

• Secondary angle closure from other causes (neovascular, inflammatory, traumatic)
• Primary open-angle glaucoma with deep angles
• Normal-tension glaucoma
• Pigmentary glaucoma
• Pseudoexfoliation glaucoma
• Plateau iris configuration without closure
• Intermittent angle closure without sustained elevation of IOP
• Non-glaucomatous optic neuropathy with narrow angles

Management

The main treatment strategy focuses on IOP reduction, reopening closed angles, and preventing further angle closure.¹ There is no universally agreed best surgical treatment for PACG.¹

Medical Management: Treatment typically begins with pressure-reducing topical medications to control IOP while monitoring changes to the angle and optic nerve head.³ Medical therapy is beneficial when combined with definitive interventions.²

Laser Procedures: Peripheral iridotomy is often performed to alleviate pupillary block and remains a cornerstone intervention.^2,3 Laser iridoplasty has been found effective for mechanisms of closure other than pupillary block, such as plateau iris syndrome.^1,3

Surgical Options: Recent evidence suggests that cataract extraction may be more effective at controlling IOP than laser or incisional glaucoma procedures.² Phacoemulsification, with or without goniosynechialysis, is a viable treatment alternative both in eyes with existing cataracts and those with clear lenses.³ Cataract and clear lens extraction may be more effective than traditional therapy in controlling IOP in patients with primary angle closure, PACG, and acute angle closure crisis.² Cataract surgery with or without trabeculectomy has been considered first-line treatment in eyes with medically uncontrolled PACG.⁶

Trabeculectomy, goniosynechialysis, glaucoma implants, and cyclodestructive procedures are effective surgical options, each playing an important role with distinct advantages and disadvantages.¹ Trabeculectomy and goniosynechialysis are often combined with cataract extraction, which may offer additional pressure control benefits.¹ Trabeculectomy remains effective therapy for more advanced cases.³ Endoscopic cyclophotocoagulation is another treatment option that can be combined with cataract surgery.³

Emerging Approaches: Minimally invasive glaucoma surgery has become an important approach, though its indications and benefits in PACG are less clear than in primary open-angle glaucoma.⁶ Future treatment strategies may include adjusting psychological status and balancing sympathetic-parasympathetic nerve activity.⁵

Prophylactic Treatment: There is limited evidence to support prophylactic treatment of primary angle closure suspects; serial gonioscopy may be the preferred approach in the absence of signs or symptoms.² Future research aims to identify which angles and persons are more likely to benefit from prophylactic treatment.⁵

Complications

Primary angle-closure glaucoma can lead to devastating visual outcomes if untreated. Progressive optic nerve degeneration results in irreversible visual field loss and potentially complete blindness. PACG is responsible for approximately half of all glaucoma-related blindness worldwide.^3,6 Acute angle closure crisis can cause rapid and severe optic nerve damage. Chronic angle closure leads to formation of peripheral anterior synechiae, which represent permanent adhesions between iris and trabecular meshwork. Surgical interventions carry procedure-specific complications, including those related to trabeculectomy (bleb-related infections, hypotony), phacoemulsification (standard cataract surgery risks), and cyclodestructive procedures (inflammation, hypotony, phthisis). The prognosis depends on early detection, appropriate intervention, and adequate IOP control.⁵

Clinical Pearls

• Gonioscopy is essential for diagnosis and cannot be replaced by other examination techniques alone.³
• PACG is most prevalent in Asian populations and demonstrates higher risk in women, elderly patients, and hyperopic individuals.³
• Multiple mechanisms beyond pupillary block contribute to angle closure, including choroidal thickness and uveal expansion.⁵
• Recent evidence increasingly supports lens extraction as highly effective therapy, even in eyes with clear lenses.^2,3
• Primary angle closure and primary open-angle glaucoma share some overlapping genetic features.⁴
• Anterior segment optical coherence tomography and ultrasound biomicroscopy can aid gonioscopy in evaluating angle structures.³
• Treatment decisions should be guided by the presence or absence of chronic angle damage and glaucomatous optic neuropathy.²

Common Pitfalls

• Failing to perform gonioscopy in patients at risk, leading to missed diagnosis of narrow angles or early closure
• Relying solely on laser peripheral iridotomy without recognizing non-pupillary block mechanisms that require alternative interventions
• Delaying definitive treatment with lens extraction in appropriate candidates while managing with suboptimal medical therapy
• Performing prophylactic procedures on primary angle closure suspects without adequate evidence of benefit or risk stratification²
• Overlooking the need for ongoing monitoring of angle anatomy and optic nerve status after initial interventions
• Assuming all angle closure is due to pupillary block and missing plateau iris or other anatomical contributors³
• Inadequately controlling IOP with medical therapy alone when surgical intervention would be more effective²