Primary Angle Closure / Primary Angle Closure Glaucoma (PAC / PACG)


Primary angle closure (PAC) is defined as appositional or synechial closure of the anterior chamber angle which can lead to aqueous outflow obstruction and raised IOP, in the absence of glaucomatous optic neuropathy. PAC is generally bilateral
Optic nerve damage resulting from PAC is described as primary angle closure glaucoma (PACG). The pooled prevalence of PACG among Caucasians of European ancestry aged 40 and over is 0.4%
PACG is caused by a variety of mechanisms although pupil block, in which aqueous is impeded on its passage between the lens and posterior surface of the iris, is considered to be a key element in its pathogenesis
Patients with angle closure disease may be categorized as follows:

Feature PAC Suspect PAC PACG
≥180 degrees ITC Present Present Present
Elevated IOP and/or PAS Absent Present Present
Optic nerve damage Absent Absent Present

(ITC = irido-trabecular contact, PAS = peripheral anterior synechiae) 

Acute angle closure (AAC) crisis: typically PAC and PACG develop chronically without symptoms, however an acute rise in IOP (unilateral in 90% of cases) can present as a clinical emergency

Predisposing factors


Associated with:

  • sex (F:M ratio 3:1)
  • ethnicity (e.g. Chinese, Vietnamese, Inuit). PACG is recognized as a leading cause of blindness in East Asia
  • family history
  • short axial length (hypermetropia)
  • shallow AC (F>M)
  • increasing age (AC becomes shallower as lens thickness increases)
  • small corneal diameter

Iatrogenic (secondary angle closure)

  • Drug induced (topical and systemic, see Evidence Base)

Adrenergic agents e.g. phenylephrine

Drugs with anticholinergic effects e.g. tricyclic antidepressants

Drugs that may cause ciliary body oedema, e.g. topiramate, sulphonamides

  • Surgery induced

Angle closure may follow a number of surgical procedures, for example vitreo-retinal surgery with intraocular gas, especially in aphakic eyes

Symptoms of primary angle closure

Patients with PAC can be asymptomatic or mildly symptomatic (ocular discomfort, headache). AAC is associated with sudden onset of symptoms and signs:

  • rapid progressive impairment of vision of one or both eyes
  • ocular and periocular pain which can be severe
  • nausea and vomiting
  • ocular redness

50% of patients with an acute angle closure attack give history of previous intermittent attacks, e.g. episodes of blurring of vision lasting 1- 2 hours, associated with haloes around lights, eye ache or frontal headache

Signs of primary angle closure

In a PAC suspect the eye may appear normal (with the exception of a narrow angle, as judged by the van Herick technique or by gonioscopy)
In cases with a narrow van Herick angle (≤ 25% [Grade 1 or 2]) with a normal anterior chamber depth, plateau iris should be suspected
In AAC the following signs may be present:

  • limbal and conjunctival vessels dilated, producing ciliary flush
  • pupil fixed, semi-dilated, vertically elliptical, iris whorling
  • corneal oedema
  • shallow AC with peripheral irido-corneal contact (if angle can be visualised)
  • high intraocular pressure (40-80mmHg)
  • AC flare and cells
  • optic disc oedematous and hyperaemic
  • grey/white anterior sub-capsular lenticular opacities (Glaukomflecken): diagnostic of previous attacks

Differential diagnosis

Neovascular glaucoma
Phakolytic glaucoma
Phakomorphic glaucoma
Acute anterior uveitis
Uveitis with raised IOP
Malignant glaucoma (cilio-lenticular block or aqueous misdirection glaucoma)

Management by optometrist

Practitioners should recognise their limitations and where necessary seek further advice or refer the patient elsewhere

GRADE* Level of evidence and strength of recommendation always relates to the statement(s) immediately above


Potentially occludable angle as judged by van Herick test
NICE does not provide guidance on referral for angle closure; however SIGN recommends that patients with peripheral anterior chamber width of ≤25% of the corneal thickness (van Herick Grade 1 or 2) should be referred to secondary eyecare services
(GRADE*: Level of evidence=low, Strength of recommendation=strong)

PAC Suspect
Can only be diagnosed by gonioscopy. The decision to refer for further treatment should be based on the risk of developing PAC/PACG or AAC. If not referring for further investigation, patients with PACS require close monitoring and serial gonioscopy. Patients should be aware that they are at risk of occlusion and that certain medications could induce angle closure
(GRADE*: Level of evidence=low, Strength of recommendation=strong)

The current clinical consensus is that patients with PAC/PACG should be treated surgically (peripheral iridotomy or cataract extraction) to relieve pupillary block together with pharmacological therapy to reduce elevated IOP
(GRADE*: Level of evidence=low, Strength of recommendation=strong)


Prior to referral, commence first aid treatment with a drop of pilocarpine 2% eye drops in blue eyes and 4% eye drops in brown eyes (although this is likely to be ineffective when IOP is over 40mmHg and paradoxically pilocarpine can exacerbate angle closure by inducing anterior lens movement)
(GRADE*: Level of evidence=low, Strength of recommendation=weak)

Where the IOP is 40mmHg or higher and the patient is not vomiting, give a single dose of oral acetazolamide (Diamox) 500mg (not slow release formulation). (NB: Diamox may be hazardous in an elderly frail patient.) Then refer as an emergency to ophthalmologist. (In view of potential unwanted effects of this treatment, patient should be accompanied by a carer or relative)
(GRADE*: Level of evidence=low, Strength of recommendation=strong)

Management category

A2: first aid measures and emergency (same day) referral to ophthalmologist

A3: urgent (within one week) referral to ophthalmologist; no intervention
PAC Suspect

A3 (modified): routine referral to ophthalmologist; no intervention

Possible management by ophthalmologist

AAC: treatment directed to breaking the pupil block and reducing IOP


  • miotics (e.g. gutt. pilocarpine 2-4%)
  • systemic agents (e.g. acetazolamide, glycerol)
  • topical antihypertensives (e.g. gutt. timolol, gutt. dorzolamide, gutt. brimonidine)

Urgent interventions

  • anterior chamber paracentesis (occasionally used in advance of peripheral iridotomy)
  • argon laser peripheral iridoplasty (occasionally used in advance of YAG laser peripheral iridotomy [LPI])
  • LPI

Less urgent interventions

  • cataract surgery
  • clear lens extraction
  • selective laser trabeculoplasty, post LPI

PAC / PACG: first line treatment options include:

  • topical medical therapy
  • LPI (for patients with PACG)
  • early (clear) lens extraction (a recent RCT found that clear lens extraction showed greater efficacy and was more cost-effective than LPI)

Evidence base

*GRADE: Grading of Recommendations Assessment, Development and Evaluation (

Sources of evidence

American Academy of Ophthalmology Glaucoma Panel. Preferred Practice Pattern Guidelines: Primary Angle Closure. San Francisco, CA: American Academy of Ophthalmology; 2015.

Azuara-Blanco A, Burr J, Ramsay C, Cooper D, Foster PJ, Friedman DS, Scotland G, Javanbakht M, Cochrane C, Norrie J; EAGLE study group. Effectiveness of early lens extraction for the treatment of primary angle-closure glaucoma (EAGLE): a randomised controlled trial. Lancet. 2016;388(10052):1389-1397

Dabasia PL, Edgar DF, Murdoch IE, Lawrenson JG. Non-contact screening methods for the detection of narrow anterior chamber angles. Invest Ophthalmol Vis Sci. 2015;56:3929-35

Day AC, Baio G, Gazzard G, Bunce C, Azuara-Blanco A, Munoz B, Friedman DS, Foster PJ. The prevalence of primary angle closure glaucoma in European derived populations: a systematic review. Br J Ophthalmol. 2012;96(9):1162-7

Hui X, Michelessi M. Medical interventions for treating primary angle-closure glaucoma. Cochrane Database of Systematic Reviews 2015;12:CD012001

Lachkar Y, Bouassida W. Drug-induced acute angle closure glaucoma Curr Opin Ophthalmol 2007;18:129-33

Napier ML, Azuara-Blanco A. Changing patterns in treatment of angle closure glaucoma. Curr Opin Ophthalmol. 2018;29(2):130-4

Rich R. The pilocarpine paradox. Journal of Glaucoma. 1996;5:225-7

Plain language summary

Primary Angle Closure Glaucoma (PACG) is rarer in this country than Primary Open Angle Glaucoma, and in its acute form differs in that the drainage route for the fluid inside the eye is closed off, rather than gradually blocked. It affects women more often than men, is commoner in long-sighted people and people of East Asian ancestry, and becomes more likely to occur as people age. Certain drugs and eye operations can also cause the drainage angle to close.

A sudden complete closure of the drainage route (known as acute angle closure crisis), which usually affects just one eye, causes rapidly progressing impairment of vision, redness of the eye, and pain in and around the eye which may be so severe as to cause nausea and vomiting. The eye pressure may be very high, because the fluid continues to be formed within the eye but cannot drain away. Various other changes will be seen in the eye by the examining optometrist.

An acute attack of angle closure is an emergency which needs same-day referral to the ophthalmologist. There are drugs that the optometrist can use as first aid. The ophthalmologist will also prescribe drugs and may advise laser treatment to create a tiny hole in the iris (the coloured part of the eye) through which the fluid can drain.

If at a routine eye examination there are signs that there have been earlier, milder attacks of angle closure, or if it appears that a patient could develop PACG, the referral can be urgent, or may be made with less urgency.

Glaucoma (primary angle closure) (PACG)
Version 15
Date of search 15.12.17
Date of revision 19.04.18
Date of publication 09.05.18
Date for review 14.12.19
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