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.
Definition
Chronic open-angle glaucoma is progressive optic neuropathy with loss of retinal ganglion-cell axons, optic-disc cupping and corresponding visual-field loss in the presence of an open iridocorneal angle. It is usually associated with raised intraocular pressure but can occur at normal pressure.
First principles
An open angle does not mean normal outflow
Aqueous humour drains through the trabecular meshwork and Schlemm’s canal at the iridocorneal angle. In COAG the angle remains open, but outflow resistance increases, so intraocular pressure may rise. Pressure is a major modifiable risk factor, but glaucoma is defined by optic-nerve and field damage rather than by a pressure number alone.
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