Chronic Open-Angle Glaucoma (COAG)
Chronic open-angle glaucoma is progressive optic-nerve damage with an open drainage angle and corresponding visual-field loss; it is usually painless and peripheral vision is lost first, so diagnosis depends on structured testing and treatment aims to prevent further irreversible loss.
In a nutshell
COAG is progressive optic-nerve and visual-field damage with an open angle, often but not always with raised intraocular pressure. It is painless and peripheral vision is lost first. Confirm with Goldmann pressure, optic-nerve/OCT assessment, standard automated perimetry and angle assessment. NICE recommends 360° SLT as initial treatment when suitable, then a generic prostaglandin analogue if laser is declined, unsuitable or insufficient; escalation and lifelong monitoring are specialist-led.
Classic presentation
An asymptomatic older patient is referred after a sight test shows a suspicious cupped disc, repeatable arcuate field defect and/or raised Goldmann pressure, with an open angle and preserved central acuity.
Key points
- The angle is open; pressure may be raised, but glaucoma is defined by optic-nerve damage and corresponding field loss.
- Use Goldmann applanation, optic-nerve/OCT assessment, standard automated perimetry and gonioscopy/angle assessment rather than pressure alone.
- Peripheral field loss is often silent; central acuity can remain good until advanced disease.
- NICE recommends 360° SLT first-line for newly diagnosed COAG when suitable, with a generic prostaglandin analogue when laser is declined, unsuitable or insufficient.
- After medicines from two classes, consider SLT or glaucoma surgery; the target pressure is individualised to progression risk.
- Lost optic-nerve tissue and field are irreversible, so adherence and risk-based lifelong monitoring matter.
First-line investigation
Goldmann applanation tonometry, optic-nerve/fundus and OCT assessment, standard automated perimetry, angle assessment and central corneal thickness, interpreted together.
Management
Recognise angle-closure or advanced-risk features
- Sudden painful red eye, haloes, nausea/vomiting or a fixed mid-dilated pupil is an angle-closure emergency; advanced field loss threatening fixation also needs expedited specialist review.1
Complete structured glaucoma assessment
- Use Goldmann pressure, optic-nerve/OCT assessment, standard automated perimetry, angle assessment and central corneal thickness; do not diagnose from pressure alone.1
Offer SLT when suitable
Add drops, laser or surgery to reach target
Exam traps
- A high pressure alone is ocular hypertension, not automatically glaucoma; a normal pressure does not exclude normal-tension glaucoma.
- Do not base referral solely on non-contact tonometry; confirm using Goldmann-type applanation and the full assessment.
- COAG is painless and peripheral field loss is often unnoticed; sudden painful red eye with haloes suggests acute angle closure.
- SLT can delay drops but does not cure glaucoma or remove the need for follow-up.
- A thin central cornea can make measured pressure underestimate risk, but no single correction replaces clinical assessment.
Illustrations
Key sources
- NICE NG81, Glaucoma: diagnosis and management (NG81)Updated 26 Jan 2022
- NICE NG81, information for the public (Glaucoma: the care you should expect)Updated 26 Jan 2022
- NICE NG81, rationale and impact: selective laser trabeculoplasty (NG81 rationale and impact)Updated 26 Jan 2022
- BNF, Latanoprost (BNF drug monograph: latanoprost)
This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.