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


Primary Angle Closure Glaucoma (PACG) is a chronic optic neuropathy associated with a loss of retinal ganglion cells and their axons which typically affects the elderly. PACG has been estimated to affect 0.4% of European-derived populations aged 40 and over and 0.94% of those ≥70 years. Rates are 2-3 times higher in Chinese and South Asian populations compared to Europeans.  PACG carries a greater risk of severe visual impairment compared with Chronic Open Angle Glaucoma.

Angle closure 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 most common (up to 75% of cases). Non-pupil block causes include plateau iris and lens-induced (i.e. through intumescence or instability) angle closure.

Staging of angle closure disease:

  • Primary Angle Closure Suspect (PACS)
  • Primary Angle Closure (PAC)
  • Primary Angle Closure Glaucoma (PACG).

Primary Angle Closure Suspect (PACS): represents the first stage, in which there is reversible contact between the peripheral iris and trabecular meshwork (irido-trabecular contact [ITC] in at least two quadrants). IOP is normal, there are no acquired adhesions between the iris and angle structures (peripheral anterior synechiae [PAS]), and no evidence of optic nerve damage.

Primary Angle Closure (PAC): is the second stage in which the IOP is elevated and/or PAS are present.  There is no evidence of glaucomatous optic neuropathy at this stage.

Primary Angle Closure Glaucoma (PACG): is the final stage in which glaucomatous optic neuropathy has developed.  In its chronic form, IOP may be normal or elevated and is often painless and asymptomatic.

ITC ≥180ºPresentPresentPresent
Elevated IOP and/or PASAbsentPresentPresent
Optic neuropathyAbsentAbsentPresent

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

An acute presentation of angle closure is a well-known ophthalmic emergency.  Acute Angle Closure crisis (AAC) results from a sudden rise in IOP (unilateral in 90% of cases) with acute symptoms (blurring, haloes and pain)

Predisposing factors

Associated with: 

  • sex (F:M ratio 3:1)
  • ethnicity (e.g. Chinese, Vietnamese, Inuit).  PACG is recognised 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 mydriatics
  • increasing pupillary block e.g. adrenergic agents such as phenylephrine, systemic drugs with anticholinergic effects such as tricyclic antidepressants, selective serotonin reuptake inhibitors
  • non-pupillary block mechanism e.g. drugs that may cause ciliary body oedema, such as 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

Typically patients with angle closure disease are asymptomatic, due to the chronic nature of the condition. Patients become symptomatic only when the disease is more advanced (e.g. ocular/periocular pain, 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 a 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

Gonioscopy remains the reference standard for confirming ITC and diagnosing angle closure, although non-invasive tests e.g. slit-lamp grading of limbal anterior chamber depth (van Herick technique) or anterior segment imaging using OCT are useful for case-finding.

In PACS the eye may appear normal (with the exception of a narrow drainage angle, as judged by limbal anterior chamber depth <25% of corneal thickness (van Herick <grade 2) or ITC visible on anterior segment OCT).

PAC is additionally associated with elevated IOP and/or PAS.

In AAC the following signs may be present:

  • limbal and conjunctival vessels dilated, producing ciliary flush
  • ‘red eye’ 
  • 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 work within their scope of practice, 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



In the light of new evidence of a low risk of glaucomatous optic neuropathy or AAC in people with PACS, the decision to refer for possible treatment with laser peripheral iridotomy, or lens extraction as an alternative, should be based on the risk of developing PAC/PACG or AAC (see Management Category). In PACS without additional risk factors for angle closure, referral and treatment are usually unnecessary (though patients should be informed of the symptoms of AAC and advised to return immediately should these occur). However, there may be a case for expediting cataract surgery in patients with significant lens opacities

(GRADE*: Level of evidence=moderate, Strength of recommendation=strong)

If not referring for further investigation, a person with PACS should be advised to seek an annual examination. Patients should be made aware that although they are at a low risk of angle closure, certain medications (e.g. pupil dilatation for fundus examination, SSRI antidepressants) 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 (clear lens/cataract removal and/or YAG laser peripheral iridotomy [LPI]) to relieve pupillary block together with pharmacological therapy to reduce elevated IOP

(GRADE*: Level of evidence=moderate, 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). Consider repeating the dose after 15 min

(GRADE*: Level of evidence=low, Strength of recommendation=strong)

Although the use of topical pilocarpine may be beneficial in pupil block and plateau iris situations (75% of cases), it may be harmful when the cause is lens-induced or retro-lenticular.

Analgesia and anti-emesis if necessary.  Where the patient is not vomiting, give a single dose of oral acetazolamide (Diamox) 500mg (not slow release formulation). (NB: acetazolamide may be hazardous in elderly patients, and is contraindicated in people with sickle cell disease or trait.) 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 


B1: routine referral to ophthalmologist (no intervention) only if limbal anterior chamber depth is <25% or an anterior segment OCT showing ITC, PLUS at least one of the following criteria:

  • people with only one ‘good’ eye
  • vulnerable adults who may not report ocular or vision symptoms
  • family history of significant angle closure disease
  • high hypermetropia (> +6.00 dioptres)
  • diabetes or another condition necessitating regular pupil dilation
  • those using antidepressants or medication with an anticholinergic action (see for details of drugs with anticholinergic properties)
  • people living in remote locations where rapid access to emergency ophthalmic care is not possible.

If an individual has the angle-characteristics specified above but none of the above additional criteria, and does not meet NICE glaucoma referral guidelines (based on IOP ≥24mm Hg or presence of signs of glaucoma) they should be advised to seek an annual examination.

Although pharmacological pupil dilatation as part of routine eye care can cause a small increase in IOP in PACS eyes (typically <5mmHg), the risk of AAC is very low.

Possible management in secondary care or local primary/community pathways where available

Additional guidance may be available

AAC: for pupillary block mechanisms, treatment directed to breaking the pupil block and reducing IOP.


  • systemic agents (e.g. acetazolamide) 
  • topical anti hypertensives (e.g. gutt. timolol, gutt. dorzolamide, gutt. brimonidine, gutt pilocarpine).

Urgent interventions 

  • argon laser peripheral iridoplasty (occasionally used in advance of YAG LPI when the cornea is cloudy and LPI cannot be performed)
  • LPI.

Less urgent interventions

  • clear lens/cataract removal.

AAC: for non-pupillary block mechanism with ciliary body oedema (e.g. due to topiramate) YAG LPI and cycloplegics are used instead of pilocarpine.

PAC / PACG: first line treatment options include:

  • topical medical therapy
  • LPI 
  • early (clear) lens extraction in people over 50 years of age (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

Baskaran M, Kumar RS, Friedman DS, Lu QS, Wong HT, Chew PTK, Lavanya R, Narayanaswamy A, Perera SA, Foster PJ, Aung T. The Singapore Asymptomatic Narrow Angles Laser Iridotomy Study: five-year results of a randomized controlled trial. Ophthalmology. 2022;129(2):147-158

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

European Glaucoma Society (2020). Terminology and Guidelines for Glaucoma. 5th Edition

He M, Jiang Y, Huang S, Chang DS, Munoz B, Aung T, Foster PJ, Friedman DS. Laser peripheral iridotomy for the prevention of angle closure: a single-centre, randomised controlled trial. Lancet. 2019;393(10181):1609-1618.

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

Jindal A, Ctori I, Virgili G, Lucenteforte E, Lawrenson JG. Non-contact tests for identifying people at risk of primary angle closure glaucoma. Cochrane Database of Syst Rev 2020;5: CD012947

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

Murray D. Emergency management: angle-closure glaucoma Comm Eye Health. 2018;31/103:64

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

NICE Guideline NG81 (2017, updated 2022). Glaucoma: diagnosis and management

Ong AY, Ng SM, Vedula SS, Friedman DS. Lens extraction for chronic angle-closure glaucoma. Cochrane Database Syst Rev. 2021;3(3):CD005555 

Ritch R. The pilocarpine paradox. Journal of Glaucoma. 1996;5:225-7 (no abstract)

Royal College of Ophthalmologists. 2022. Management of angle closure glaucoma guideline.

Sun X, Dai Y, Chen Y, Yu DY, Cringle SJ, Chen J, Kong X, Wang X, Jiang C. Primary angle closure glaucoma: What we know and what we don't know. Prog Retin Eye Res. 2017;57:26-45

Tanner L, Gazzard G, Nolan WP, Foster PJ. Has the EAGLE landed for the use of clear lens extraction in angle-closure glaucoma? And how should primary angle-closure suspects be treated? Eye (Lond). 2020;34(1):40-50

Wang L, Huang W, Han X, Liao C, Jin L, He M. The Impact of Pharmacological Dilation on Intraocular Pressure in Primary Angle Closure Suspects. Am J Ophthalmol. 2022;235:120-130


What is Primary Angle Closure / Primary Angle Closure Glaucoma?

The shape of the outer edge of the iris and the drainage channel for the fluid inside the eye (a space known as ‘the angle’) varies from person to person.  This space is normally open, so that the fluid can drain freely, but if the edge of the iris and the drainage channel comes into contact from time to time, the patient is described as a Primary Angle Closure Suspect (PACS). There are no adhesions, there is no rise in eye pressure or evidence that damage to the optic nerve has been caused through raised eye pressure in the past. A condition called Primary Angle Closure (PAC) is present if the eye pressure is raised and/or adhesions between the iris and the drainage channel are present, but there is no damage to the optic nerve (the nerve of sight). If there is damage to the optic nerve caused by rises in eye pressure, the condition is described as Primary Angle Closure Glaucoma (PACG). In this country, this form of glaucoma is rarer than Primary Open Angle Glaucoma (POAG), but it carries a greater risk of damage to vision. This condition 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 angle (known as Acute Angle Closure crisis, AAC), 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.

How is Primary Angle Closure / Primary Angle Closure Glaucoma managed?

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 (‘YAG laser’) to create a tiny hole in the iris (the coloured part of the eye) through which the fluid can drain. Treatment to the edge of the iris using a different kind of laser (argon laser peripheral iridoplasty) may also be advised. Later, further surgery may be recommended.

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.

Glaucoma (Primary Angle Closure and Primary Angle Closure Glaucoma) (PAC / PACG)
Version 16
Date of search 15.03.22
Date of revision 14.04.22
Date of publication 27.06.22
Date for review 14.03.24
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