Angle Closure Glaucoma Definitions
Last updated: September 2026
The ISGEO (International Society for Geographical and Epidemiological Ophthalmology) classification remains the standard framework for staging angle closure disease — precise terminology here matters because it directly determines management.
Definitions
| Term | Gonioscopy | Other findings |
|---|---|---|
| Primary angle-closure suspect (PACS) | Posterior trabecular meshwork iridotrabecular contact (ITC) in three or more quadrants, but no peripheral anterior synechiae (PAS) | Normal IOP, optic disc, and visual field. A lower threshold — even two quadrants of ITC, or a narrow angle approach of ~20° — may still justify the diagnosis in some patients showing evidence of intermittent angle closure |
| Primary angle-closure (PAC) | Three or more quadrants of ITC, with raised IOP and/or PAS, or excessive pigment smudging on the trabecular meshwork | Normal optic disc and visual field — the key distinction from PACG is the absence of glaucomatous optic neuropathy |
| Primary angle-closure glaucoma (PACG) | ITC in three or more quadrants | Glaucomatous optic neuropathy present — this is what separates PACG from PAC |
Current diagnostic addition: AS-OCT alongside gonioscopy
While gonioscopy remains the clinical reference standard for angle assessment, anterior segment OCT is now widely used as a complementary, non-contact tool — particularly useful for objective, reproducible angle measurements and for patients where gonioscopy is difficult (photophobia, corneal haze, or poor cooperation).
Important current shift in first-line management
Randomized trial evidence (including the EAGLE trial) has shown that in select patients — particularly acute primary angle closure and PACG with elevated IOP — clear lens extraction can outperform laser peripheral iridotomy (LPI) as an initial treatment, by permanently deepening the anterior chamber rather than simply creating a pressure-equalizing bypass. This has meaningfully shifted first-line thinking in some angle-closure scenarios, especially when a visually significant cataract already coexists — worth knowing as current evidence-based practice rather than defaulting reflexively to "LPI for everyone."
Key references: Weinreb RN, et al. Primary angle-closure disease: ISGEO classification. | Day AC, et al. EAGLE trial: clear lens extraction for primary angle closure glaucoma. Lancet.
📘 Want the exam-ready deep dive? This topic is covered in iNotes 2027: Glaucoma (Ophthalmology Postgraduate Exam Notes) — available on Kindle. See all my books.
Want to know more about treatment? Read about Glaucoma Treatment at Sadbhaav or book a consultation with Dr. Dhaval Patel.