Closed-angle glaucoma (CAG) is an eye disorder in which the coloured part of the eye (iris) and the lens block the movement of fluid between the chambers of the eye. Closed-angle glaucoma is also called angle-closure glaucoma.

The blockage of fluid causes pressure to build up in the eye. This causes the iris to press on the drainage system (trabecular meshwork) of the eye. The increased pressure can cause damage to the optic nerve, which leads to vision loss and possible blindness. CAG can happen suddenly, or it can develop slowly over time.

Acute closed-angle glaucoma may cause sudden blurred vision with pain and redness, usually in one eye first. It can be an emergency situation that needs immediate medical care to prevent lasting damage to the affected eye. Treatment usually includes surgery, but may include medicines to lower the pressure in the eye if surgery can't be done right away. The opposite eye is usually examined too and eventually treated, because the condition is likely to affect this eye.

CAG that develops slowly is called chronic closed-angle glaucoma. It happens when scar tissue forms between the iris and the drainage system.