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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Ophthalmology

Anatomy & Subtypes: The PACG Spectrum

At a Glance

Primary angle-closure glaucoma (PACG) is caused by physical crowding in the eye that blocks normal fluid drainage. The condition progresses through three stages: Suspect (PACS), Closure (PAC), and Glaucoma (PACG). Identifying your exact stage and anatomical risk factors is critical for preventing irreversible vision loss.

Primary angle-closure glaucoma is not just a single event; it is the final stage of a physical “crowding” within the eye. Understanding your specific anatomy and where you fall on the disease spectrum is essential for determining how urgently you need treatment.

The “Crowded” Eye: Anatomical Causes

Most people with angle-closure have eyes that are built slightly differently than average. Because these differences are often inherited, your family history is one of the strongest predictors of your risk [1]. Because the anatomical traits that cause PACG are highly heritable, you should strongly advise your first-degree relatives to ask their eye doctors for a gonioscopy [2].

  • Hypermetropia (Farsightedness): People who are farsighted often have “shorter” eyes (measured as axial length). In a shorter eye, there is less physical space for all the internal structures, leading to overcrowding at the front of the eye [3][2].
  • Lens Vault: The eye’s natural lens sits just behind the iris. If the lens is thicker or positioned further forward—a measurement doctors call lens vault—it can push the iris forward, narrowing the drainage angle [4][5].
  • Plateau Iris: This is a specific anatomical variant where the ciliary body (the structure that holds the lens) is positioned too far forward. This creates a “shelf” that props the iris up against the drainage wall, even if other parts of the eye seem normal [6][7].
  • Ethnicity: PACG is significantly more common in individuals of Asian descent, largely due to naturally occurring differences in eye shape and size [8][9].

The PACG Spectrum: Where Do You Fall?

Doctors use a specific three-step classification to describe how far the disease has progressed. Moving from one stage to the next is not inevitable, and treatment aims to stop you from reaching the final stage.

  1. Primary Angle-Closure Suspect (PACS): At this stage, your eye is “crowded,” and your drainage angle is narrow enough that the iris is touching the drainage wall. However, your eye pressure is normal, there is no permanent scarring, and your optic nerve is healthy. You are “at risk” but do not yet have the disease [10][11].
  2. Primary Angle-Closure (PAC): This is a more advanced stage. The physical closure of the angle has now caused a measurable problem: either your intraocular pressure (IOP) is elevated (above 24 mmHg) or permanent scar tissue (called Peripheral Anterior Synechiae or PAS) has begun to form in the drain. Despite these signs of “active” closure, there is still no damage to the optic nerve [10][12].
  3. Primary Angle-Closure Glaucoma (PACG): This is the final stage. The physical blockage of the drain has caused the eye pressure to damage the optic nerve, leading to irreversible vision loss. Treatment at this stage is focused on saving the remaining vision and preventing further decline [13][14].

Why Classification Matters

Your doctor uses tests like gonioscopy or AS-OCT (a high-tech scan of the front of the eye) to determine your exact stage [15][16]. If you are a “Suspect” (PACS), your doctor might choose to monitor you closely. However, if you have reached the “Closure” (PAC) or “Glaucoma” (PACG) stages, definitive treatment—such as lens extraction or laser iridotomy—is typically required to open the angle and protect your sight [17][18].

Common questions in this guide

What is the difference between PACS, PAC, and PACG?
PACS means you have a crowded eye and narrow drainage angles, but no damage has occurred yet. PAC indicates that the closure is actively causing high eye pressure or scarring. PACG is the final stage where the elevated pressure has caused irreversible damage to the optic nerve.
Why does being farsighted increase my risk for angle-closure glaucoma?
Farsighted individuals often have physically shorter eyes, which means there is less room for internal structures. This lack of space causes overcrowding at the front of the eye, making the drainage angle narrower and more prone to blockage.
What does it mean if my doctor says I have a plateau iris?
Plateau iris is an anatomical variant where the structure holding the eye's natural lens is positioned unusually far forward. This creates a shelf-like effect that props the iris up against the drainage wall, increasing your risk of angle closure even if other parts of the eye are normal.
Should my family members be tested if I have primary angle-closure glaucoma?
Yes, you should strongly advise your first-degree relatives to get screened. The anatomical traits that cause a crowded eye are highly inherited, so family members should ask their eye doctor for a specific diagnostic test called a gonioscopy.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Am I currently classified as a 'Suspect' (PACS) or do I have evidence of 'Closure' (PAC) or 'Glaucoma' (PACG)?
  2. 2.Does my anatomy show 'Plateau Iris' features, and if so, how that change my treatment plan compared to standard pupillary block?
  3. 3.How much is my lens contributing to the 'crowding' in my eye, and would early lens removal be more effective than a laser for my specific eye shape?
  4. 4.Are there specific signs of scarring (Peripheral Anterior Synechiae) in my drainage angle that suggest the closure has been happening for a long time?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (18)
  1. 1

    Prevalence and Risk Factors of Primary Angle Closure Disease in an Adult Chinese American Population: The Chinese American Eye Study.

    Xu BY, Richter GM, Burkemper BS, et al.

    American journal of ophthalmology 2025; (274()):32-41 doi:10.1016/j.ajo.2025.02.037.

    PMID: 40023353
  2. 2

    GWAS for primary angle-closure glaucoma identifies loci related to ocular biometry and morphology.

    Luben RN, Biradar MI, Stuart KV, et al.

    Nature communications 2025; (16(1)):10003 doi:10.1038/s41467-025-64949-z.

    PMID: 41238566
  3. 3

    HLA-DPA1 gene polymorphism in primary glaucoma.

    Li JH, Shao JF, Sui ZG, Qin YX

    European review for medical and pharmacological sciences 2019; (23(3 Suppl)):24-30 doi:10.26355/eurrev_201908_18623.

    PMID: 31389567
  4. 4

    Novel diagnostic indicators for acute angle closure secondary to lens subluxation based on anterior segment and lens parameters.

    Tang Y, Gao Y, Yu X, et al.

    Heliyon 2024; (10(3)):e25164 doi:10.1016/j.heliyon.2024.e25164.

    PMID: 38327450
  5. 5

    Qualitative and quantitative evaluation of acute angle-closure mechanisms.

    Suwan Y, Jiamsawad S, Tantraworasin A, et al.

    BMC ophthalmology 2017; (17(1)):246 doi:10.1186/s12886-017-0635-8.

    PMID: 29228915
  6. 6

    PLATEAU IRIS--DIAGNOSIS AND TREATMENT.

    Stefan C, Iliescu DA, Batras M, et al.

    Romanian journal of ophthalmology 2015; (59(1)):14-8.

    PMID: 27373109
  7. 7

    Exploring the Occurrence Mechanisms of Acute Primary Angle Closure by Comparative Analysis of Ultrasound Biomicroscopic Data of the Attack and Fellow Eyes.

    Wang F, Wang D, Wang L

    BioMed research international 2020; (2020()):8487907 doi:10.1155/2020/8487907.

    PMID: 32382576
  8. 8

    Phacoemulsification vs phacoemulsification with micro-bypass stent implantation in primary angle closure and primary angle closure glaucoma: A randomized single-masked clinical study.

    Chen DZ, Sng CCA, Sangtam T, et al.

    Clinical & experimental ophthalmology 2020; (48(4)):450-461 doi:10.1111/ceo.13721.

    PMID: 32003538
  9. 9

    Anterior Segment Biometry in Primary Angle Closure Glaucoma Patients with Visual Field Progression: Comparison between Malays and Chinese.

    Neoh FP, Y A, Siti AA, Liza-Sharmini AT

    Journal of current glaucoma practice 2023; (17(1)):3-8 doi:10.5005/jp-journals-10078-1391.

    PMID: 37228307
  10. 10

    Ocular Biometric Risk Factors for Progression of Primary Angle Closure Disease: The Zhongshan Angle Closure Prevention Trial.

    Xu BY, Friedman DS, Foster PJ, et al.

    Ophthalmology 2022; (129(3)):267-275 doi:10.1016/j.ophtha.2021.10.003.

    PMID: 34634364
  11. 11

    Prevalence of Primary Glaucoma as Diagnosed by Study Optometrists of L. V. Prasad eye Institute - Glaucoma Epidemiology and Molecular Genetics Study.

    Addepalli UK, Jonnadula GB, Garudadri CS, et al.

    Ophthalmic epidemiology 2019; (26(3)):150-154 doi:10.1080/09286586.2018.1551961.

    PMID: 30489169
  12. 12

    Prevalence and risk factors for primary angle-closure disease spectrum: The Colombian glaucoma study.

    Martínez-Blanco AM, Cantor EJ, Valencia-Peña C

    European journal of ophthalmology 2021; 11206721211060153 doi:10.1177/11206721211060153.

    PMID: 34796746
  13. 13

    Blindness in glaucoma: primary open-angle glaucoma versus primary angle-closure glaucoma-a meta-analysis.

    George R, Panda S, Vijaya L

    Eye (London, England) 2022; (36(11)):2099-2105 doi:10.1038/s41433-021-01802-9.

    PMID: 34645961
  14. 14

    Fifteen-Year Incidence Rate of Primary Angle Closure Disease in the Andhra Pradesh Eye Disease Study.

    Choudhari NS, Khanna RC, Marmamula S, et al.

    American journal of ophthalmology 2021; (229()):34-44 doi:10.1016/j.ajo.2021.02.030.

    PMID: 33667399
  15. 15

    Proportion of Angle Closure Glaucoma in Tamale, Ghana.

    Liu CK, Ali O, Murdoch I, Simon J

    Journal of glaucoma 2024; (33(9)):709-714 doi:10.1097/IJG.0000000000002383.

    PMID: 38551403
  16. 16

    Anterior Segment Optical Coherence Tomography: Applications for Clinical Care and Scientific Research.

    Shan J, DeBoer C, Xu BY

    Asia-Pacific journal of ophthalmology (Philadelphia, Pa.) 2019; (8(2)):146-157 doi:10.22608/APO.201910.

    PMID: 31020820
  17. 17

    Predictors of long-term intraocular pressure control after lens extraction in primary angle closure glaucoma: results from the EAGLE trial.

    Mitchell WG, Azuara-Blanco A, Foster PJ, et al.

    The British journal of ophthalmology 2023; (107(8)):1072-1078 doi:10.1136/bjophthalmol-2021-319765.

    PMID: 35387778
  18. 18

    Changing patterns in treatment of angle closure glaucoma.

    Napier ML, Azuara-Blanco A

    Current opinion in ophthalmology 2018; (29(2)):130-134 doi:10.1097/ICU.0000000000000453.

    PMID: 29194069

This page explains the anatomy and stages of primary angle-closure glaucoma for educational purposes only. It does not replace professional medical advice. Always discuss your specific eye anatomy, diagnostic scans, and treatment options with your ophthalmologist.

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