Chronic Open‑Angle Glaucoma
Introduction
Chronic open‑angle glaucoma (COAG) is a progressive optic neuropathy caused by impaired aqueous outflow through an anatomically open anterior chamber angle. The result is progressive loss of retinal ganglion cell axons at the optic nerve head, producing characteristic optic disc cupping and irreversible peripheral visual field loss.
Early disease is usually painless and asymptomatic, so COAG is often undiagnosed until substantial field loss has occurred.
NICE NG81 is the principal UK guideline for diagnosis, referral and management; routine population screening is not recommended (UK NSC), so case‑finding in at‑risk groups is the standard approach.
Epidemiology and risk groups
- Prevalence: approximately 1 in 50 adults over 40, rising with age (≈1 in 10 over 75).
- Higher risk groups: family history of glaucoma; people of African/Afro‑Caribbean descent; myopia; ocular hypertension; long‑term topical or systemic steroids; previous intraocular surgery.
- Systemic vascular risk factors associated with progression: diabetes and cardiovascular disease.
- Note: normal‑tension glaucoma exists - optic neuropathy can progress despite IOP in the “normal” range.
Pathophysiology (concise)
- The anterior chamber angle remains anatomically open.
- The primary problem is reduced trabecular meshwork (and Schlemm’s canal) outflow, causing aqueous retention and raised intraocular pressure (IOP) in many patients.
- Chronic IOP elevation produces mechanical and vascular stress at the optic nerve head, leading to progressive retinal ganglion cell loss, neuroretinal rim thinning...