Primary and secondary
angle-closure glaucoma

Referral priority: Moderate or urgent

Patients experiencing acute angle closure attacks, whether the reason is primary or secondary, should be promptly referred to an ophthalmologist or a hospital following local guidelines.

Click on one of the cards below to read more about the specific eye condition.

Written by
Marko Lukic
Edited by
Svein Tindlund and Jon Gjelle
June 2023


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Physical examination

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Diagnostic procedures

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Management and treatment

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Glaucoma represents a substantial public health problem. It is the leading cause of irreversible blindness worldwide and is associated with a reduced quality of life.(1)

Glaucoma describes a group of progressive conditions with characteristic cupping of the optic disc with corresponding visual field defects due to retinal ganglion cell loss.(2)

In primary angle-closure glaucoma, the underlying mechanism is mainly pupillary block. At the same time, in secondary forms, there are other underlying causes that either push the iris forward from behind or pull the iris forward to contact trabecular meshwork.(3,4) Both angle-closure glaucomas may cause acute dramatic attacks or chronic asymptomatic disease. It is crucial to be familiar with the below terminology:(5)

  • Primary angle-closure suspect (PACS) or narrow anatomic angle
  • Primary angle-closure (PAC)
  • Primary angle-closure glaucoma (PACG)
  • Secondary angle-closure

Several risk factors are identified for primary angle-closure glaucoma: hyperopia, family history of angle closure, advanced age, female gender, Asian or Inuit descent, short axial length, shallow anterior chamber depth, and thick crystalline lens.(6-12)

A relative pupillary block causes primary angle-closure glaucoma in most cases. In the pupillary block, the aqueous humour encounters increased resistance to flow between posterior and anterior eye chambers. The increased pressure gradient across the pupil causes the peripheral iris to bow forward and cover some or all of the filtering portion of the trabecular meshwork, resulting in appositional angle closure. Peripheral anterior synechiae form after prolonged or repeated contact of the peripheral iris with trabecular meshwork.(3) Non-pupillary block mechanism is present in the plateau iris. A typical central anterior chamber depth, flat iris profile, and crowding of the angle by the iris base characterise plateau iris configuration. There is a forward displacement of the iris base by anteriorly located ciliary processes that can lead to subsequent angle closure.(13,14)

Mechanisms/causes of secondary angle-closure are absolute pupillary block due to 360º posterior synechiae, aqueous misdirection, swelling of the ciliary body in inflammatory conditions, choroidal swelling (i.e., choroidal detachment), scleral buckles, contracting membranes within the iridocorneal angle, iris incarceration in traumatic cases, iridocorneal endothelial syndrome.



Patients with anatomically narrow angles and primary and secondary chronic angle-closure glaucoma are usually asymptomatic. Those with advanced glaucoma complain of blurry vision and visual field defects.

Patients with acute angle closure present with sudden eye pain, conjunctival redness, and corneal oedema. The intraocular pressure is mostly between 40 and 80 mmHg. Those patients describe halos around lights and may even have transient vision loss. They often develop symptoms of nausea and vomiting.

Patients may have subacute or intermittent angle closure. They represent with milder symptoms like some blurring of the vision or halos with mild to moderate eye pain, brow ache, or headache. Symptoms are often resolved if patients go to sleep or go into a lit room.


Physical examination

Intraocular pressure measurement

The gold standard for IOP measurement is Goldmann Applanation Tonometry (GAT). Fluorescein dye is placed on the patient’s eye to highlight the tear film. A split-image prism divides the image of the tear meniscus into a superior and an inferior arc. The intraocular pressure is taken when these arcs are aligned such that their inner margins touch.(15)

Errors that may cause false IOP reading: Central corneal thickness, excessive or insufficient fluorescein in the tear film affecting the thickness of the overlapping arcs, high astigmatism, irregular or scarred cornea, pressure from a finger on the eyelid while taking the measurement, and breath holding or Valsalva manoeuvre by the patient during measurement.

Another option is rebound tonometry (iCare devices use this technique). It has a good agreement with Goldman and Tono-Pen readings. A 1.8mm diameter plastic ball on a stainless steel wire is held in place by an electromagnetic field in a battery-powered handheld device. A spring moves the wire and ball forward rapidly when a button is pushed. When the ball hits the cornea, the ball and wire decelerate; the deceleration is more rapid if the IOP is high and slower if the IOP is low. The speed of deceleration is measured and converted by the device into IOP. No anaesthetic is necessary. Central corneal thickness also affects the accuracy of IOP measurement.(15) Air Puff Tonometer, Ocular Response Analyser (ORA),  Tono-Pen, and Schiøtz  are other options to measure IOP. 

Central corneal thickness measurement

Central corneal thickness (CCT) is one of the biomechanical attributes of the cornea. Thick corneas may give false positive high IOPs, whilst thin corneas may give false average IOPs. Standard corneal thickness is considered between 540 and 560 microns. CCT may be helpful in baseline risk profiling, but despite existing IOP correction algorithms, the European Glaucoma Society suggests avoiding them.(28)

Anterior chamber angle examination

There are a few methods to examine the anterior angle: Gonioscopy on a slit lamp, ultrasound biomicroscopy, or anterior OCT.

Gonioscopy is essential to diagnose narrow or closed angles and should be performed on the initial visit. Various classification systems have been described to assess the extent of an open angle. The ideal way to perform gonioscopy is in a dark room using a small rectangle of light only as bright as necessary to view the angle structures, as light can open an appositionally closed angle in about one-third of cases. Dynamic or compression or indentation gonioscopy is essential to differentiate appositional and synechial closures. Gentle pressure on the cornea with the goniolens pushes back the iris and reveals whether the angle can be opened further; if not, synechial closure is present.(3) This manoeuvre can also help break acute attacks by forcing fluid into the periphery and opening areas of appositional closure.

Different classification systems are used to classify whether the anterior angle is closed or opened. Shaffer classification system describes the degree to which the angle is open rather than the degree to which it is closed (compared to the Scheie’s system). The Shaffer system approximates the angle at which the iris inserts relative to the trabecular meshwork.

Remember that it is difficult to perform gonioscopy in patients with acute angle-closure attacks.

Grade number Angle width Description Risk of closure
4 45° – 35° Wide open Impossible
3 35°-20° Wide open Impossible
2 20°-10° Narrow Possible
1  10° Extremely narrow Probable
Slit Slit Narrowed to slit Probable
0 0° Closed Closed

Table 1: Schaffer classification system(16)

It is important to do a thorough eye examination and look for potential causes of narrow-angle, like new vessels of the angle, cells, and keratic precipitates (KPs) in the anterior chamber, posterior synechiae, posterior segment masses, thick cataract, and anterior chamber depth.

The physical examination assesses IOP, anterior-chamber angle, optic disc, and visual-fields test.


Diagnostic procedures

Slit lamp examination/colour fundus photography is helpful in examining people with suspected glaucoma. The following features should be considered in patients with suspected glaucoma(18):

  • High cup: disc ratio
  • Cup: disc ratio asymmetry between eyes (usually considered significant if greater than 0.2)
  • Vertical elongation of cup
  • Focal neuro-retinal rim thinning or notching
  • Vessel bayoneting
  • Beta-zone peripapillary atrophy (occurs as a result of atrophy of the RPE and choriocapillaris)
  • Disc haemorrhage
Image 1. Image representing shallow anterior chamber in a patient with narrow-angle.
Image 2. Eye with narrow-angle post peripheral laser iridotomy (PLI); white arrow.

Optical coherence tomography – it is part of routine imaging in glaucoma patients. It analyses RNFL and optic nerve heads in patients with a chronic type of glaucoma.

Visual fields test – automated threshold perimetry is used to diagnose early signs of visual field defects and to monitor progression. The defects involved in POAG are:


Management and treatment

Patients suspected of having angle-closure glaucoma presenting at optometry practices should be referred to ophthalmology by specific guidelines set by the local healthcare system.


Peripheral laser iridotomy is a surgical procedure that may have a preventative effect in preventing pupillary block. Therefore, patients with narrow angles should be regularly monitored.

Management of acute angle-closure attack

The role of medical therapy in acute angle-closure attacks is to lower IOP, reduce pain, and clear corneal oedema in preparation for iridotomy:

Topical medical therapy

Always check for potential contraindications of using the below drugs: 

  • Beta-blockers
  • Selective alpha agonists
  • Carbonic anhydrase inhibitors
  • Miotics (e.g., pilocarpine 2%) may help break an early angle-closure attack but may be ineffective if the iris is already ischemic. Likewise, high-concentration miotics (e.g., pilocarpine 4%) should be avoided because of the potential for forward displacement iris-lens diaphragm.
  • Hyperosmolar agent (e.g. 5% sodium chloride) – assists in clearing corneal oedema
  • Prednisolone 1% – decreases inflammation.

Systemic medical therapy includes oral or intravenous carbonic anhydrase inhibitors and osmotic agents (i.e., intravenous mannitol). 

An experienced eye care specialist should do paracentesis. Be aware that it is only performed in cases with very high IOPs to buy time for medications to start working.

Laser iridotomy, including the contralateral eye, should be done as quickly as possible.



1 Thomas S, Hodge W, Malvankar-Mehta M. The cost-effectiveness analysis of teleglaucoma screening device. PloS one. 2015 Sep 18;10(9):e0137913.

2 Harasymowycz P, Birt C, Gooi P, Heckler L, Hutnik C, Jinapriya D, Shuba L, Yan D, Day R. Medical management of glaucoma in the 21st century from a Canadian perspective. Journal of Ophthalmology. 2016 Nov 8;2016.


4 Wright C, Tawfik MA, Waisbourd M, Katz LJ. Primary angle‐closure glaucoma: an update. Acta ophthalmologica. 2016 May;94(3):217-25.

5 Foster PJ, Buhrmann R, Quigley HA, Johnson GJ. The definition and classification of glaucoma in prevalence surveys. British Journal of Ophthalmology. 2002 Feb 1;86(2):238-42.

6 Lowe RF. Aetiology of the anatomical basis for primary angle-closure glaucoma. Biometrical comparisons between normal eyes and eyes with primary angle-closure glaucoma. The British Journal of Ophthalmology. 1970 Mar;54(3):161.

7 Perkins ES. Family studies in glaucoma. The British Journal of Ophthalmology. 1974 May;58(5):529.

8 Seah SK, Foster PJ, Chew PT, Jap A, Oen F, Fam HB, Lim AS. Incidence of acute primary angle-closure glaucoma in Singapore: an island-wide survey. Archives of ophthalmology. 1997 Nov 1;115(11):1436-40.

9 Bourne RR, Sørensen KE, Klauber A, Foster PJ, Johnson GJ, Alsbirk PH. Glaucoma in East Greenlandic Inuit: –a population survey in Ittoqqortoormiit (Scoresbysund). Acta Ophthalmologica Scandinavica. 2001 Oct;79(5):462-7.

10 van Herick W, Shaffer RN, Schwartz A. Estimation of width of angle of anterior chamber: incidence and significance of the narrow-angle. American Journal of Ophthalmology. 1969 Oct 1;68(4):626-9.

11 Sihota R, Sood A, Gupta V, Gupta V, Dada T, Agarwal HC. A prospective longterm study of primary chronic angle closure glaucoma. Acta Ophthalmologica Scandinavica. 2004 Apr;82(2):209-13.

12 Lowe RF. Aetiology of the anatomical basis for primary angle-closure glaucoma. Biometrical comparisons between normal eyes and eyes with primary angle-closure glaucoma. The British Journal of Ophthalmology. 1970 Mar;54(3):161.

13 Ritch R. Plateau iris is caused by abnormally positioned ciliary processes. J Glaucoma. 1992 Apr 1;1(1):23-6.

14 Pavlin CJ, Ritch R, Foster FS. Ultrasound biomicroscopy in plateau iris syndrome. American Journal of Ophthalmology. 1992 Apr 1;113(4):390-5.



17 Shih CY, Zivin JS, Trokel SL, Tsai JC. Clinical significance of central corneal thickness in the management of glaucoma. Archives of ophthalmology. 2004 Sep 1;122(9):1270-5.

18 Fingeret M, Medeiros FA, Susanna Jr R, Weinreb RN. Five rules to evaluate the optic disc and retinal nerve fibre layer for glaucoma. Optometry-Journal of the American Optometric Association. 2005 Nov 1;76(11):661-8.