How is angle-closure glaucoma different from open-angle glaucoma?

In angle-closure disease the peripheral iris physically blocks the drainage angle, whereas in open-angle disease the angle stays anatomically open while outflow resistance rises within the trabecular meshwork.

What is an acute angle-closure crisis?

It is a sudden, often symptomatic rise in intraocular pressure caused by abrupt closure of the drainage angle; it is considered an ophthalmic emergency and is mechanistically distinct from the slowly progressive chronic forms of angle closure.

Angle-Closure Glaucoma

Angle-closure glaucoma is the form of glaucoma in which the peripheral iris physically obstructs the anterior chamber drainage angle, impeding aqueous outflow and raising intraocular pressure. It spans a spectrum from gradual chronic closure to sudden acute attacks, and although less common overall than open-angle disease, it carries a disproportionate share of blindness in some populations.

Definition

Angle-closure glaucoma is glaucomatous optic neuropathy occurring in eyes in which apposition or adhesion of the peripheral iris to the trabecular meshwork obstructs aqueous outflow, raising intraocular pressure either gradually or acutely.

Scope

The topic covers the anatomical mechanism of angle closure, the classification spectrum from primary angle-closure suspect to established glaucoma, the contrast with open-angle disease, and the principal strategies studied to relieve or prevent closure. It is a clinical-entity reference topic and does not provide individualised diagnostic or treatment instructions.

Core questions

What anatomical configurations predispose the drainage angle to close?
How does the spectrum from primary angle-closure suspect to primary angle-closure glaucoma progress?
How does an acute angle-closure crisis differ from chronic closure?
What is the rationale for interventions that relieve pupillary block or address the lens?

Key concepts

Pupillary block
Peripheral anterior synechiae
Primary angle-closure suspect
Acute angle-closure crisis
Shallow anterior chamber
Laser peripheral iridotomy
Lens-induced angle crowding

Mechanisms

In the most common pathway, relative pupillary block impedes aqueous flow from the posterior to the anterior chamber, raising posterior-chamber pressure and bowing the peripheral iris forward against the trabecular meshwork. Predisposing anatomy includes a shallow anterior chamber, short axial length, and an enlarging lens that crowds the angle. Closure may be intermittent or chronic, allowing peripheral anterior synechiae to form, or it may occur abruptly as an acute crisis with a steep pressure rise. Relieving pupillary block and reducing lens-related crowding are the mechanistic targets of the interventions studied (Jonas 2017; Foster 2002).

Clinical relevance

Although less prevalent than open-angle glaucoma globally, angle-closure disease accounts for a large proportion of glaucoma blindness in parts of Asia, making its mechanism and classification important in ophthalmology and global eye health. Acute angle closure is an ophthalmic emergency conceptually distinct from the chronic forms. This entry describes the disease and its evidence base and is not a basis for individual diagnosis or treatment.

Epidemiology

Angle-closure glaucoma is markedly more common in East and South Asian populations and in women, and although fewer people are affected than by open-angle disease, the meta-analytic projections place a substantial and growing burden in Asia, where it contributes disproportionately to glaucoma-related blindness (Tham 2014).

Evidence & guidelines

Classification frameworks distinguish the primary angle-closure suspect, primary angle closure, and primary angle-closure glaucoma along a continuum (Foster 2002). On management strategy, the EAGLE randomised trial compared early lens extraction with laser peripheral iridotomy in primary angle-closure disease and reported outcomes favouring early lens extraction on several measures, informing how the role of the lens is understood (Azuara-Blanco 2016). Terminology and assessment are summarised in current society guidelines (European Glaucoma Society 2021).

History

Angle-closure glaucoma was long understood mainly as the dramatic acute attack, but population surveys and the work of Foster and colleagues reframed it as a spectrum anchored on the configuration of the drainage angle and the presence of optic nerve damage. Later randomised evidence shifted attention from iris-based mechanisms alone toward the contribution of the lens (Foster 2002; Azuara-Blanco 2016).

Debates

What is the optimal first intervention for primary angle-closure glaucoma?: Historically laser peripheral iridotomy addressing pupillary block was the standard first step, but the EAGLE trial reported advantages for early lens extraction, prompting reassessment of the lens's role versus iris-directed treatment.

Key figures

Paul J. Foster
Augusto Azuara-Blanco
Jost B. Jonas
Harry Quigley

Seminal works

foster-2002
azuara-blanco-2016
jonas-2017

Frequently asked questions

How is angle-closure glaucoma different from open-angle glaucoma?: In angle-closure disease the peripheral iris physically blocks the drainage angle, whereas in open-angle disease the angle stays anatomically open while outflow resistance rises within the trabecular meshwork.
What is an acute angle-closure crisis?: It is a sudden, often symptomatic rise in intraocular pressure caused by abrupt closure of the drainage angle; it is considered an ophthalmic emergency and is mechanistically distinct from the slowly progressive chronic forms of angle closure.