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What Is Narrow-Angle Glaucoma?Primary glaucoma is usually thought of as “open-angle” glaucoma, where the eye’s drainage system (the trabecular meshwork in the angle between the cornea and iris) remains open. Narrow-angle glaucoma – also called angle-closure glaucoma – is different. In these eyes the front part of the eye is crowded: the iris (the colored part) sits too close to the drainage angle, blocking fluid outflow. Tiny pores in the drainage tissue can become partially or fully sealed by the iris. This stops aqueous humor from draining normally and causes eye pressure (intraocular pressure, or IOP) to rise quickly () (). In open-angle glaucoma, pressure usually rises slowly over years and damages nerves little by little. In contrast, narrow angles can abruptly trap fluid, driving IOP sky-high in hours – a spike that can destroy optic nerve fibers very quickly if untreated () (). High pressure in the eye leads to irreversible vision loss if not relieved. In fact, studies show angle-closure glaucoma causes blindness far more often than open-angle disease (). Although rare compared to open-angle glaucoma, angle-closure attacks can be catastrophic. It is one of the few true eye emergencies, because vision can be lost in a matter of hours without treatment () (). Anatomy: Closed Angle vs. Open AngleTo understand narrow angles, imagine the anterior chamber of the eye (space between cornea and iris) as a bowl. In open-angle glaucoma this bowl is deep enough that fluid (the aqueous humor) easily flows through the angle at the periphery. In narrow-angle glaucoma, the inner wall of the bowl (iris) bows forward toward the outer wall (cornea). This flattens and narrows the angle through which fluid drains () (). A helpful way ophthalmologists define angle-closure is by how much the iris touches the trabecular meshwork. If more than half of the meshwork is blocked by iris contact, the angle is considered “closed” (). In practice, doctors use gonioscopy – a special contact lens with mirrors – to shine light into the angle and see how open it is (). With gonioscopy they can see if the iris is bumping into the drainage site. In short, angle-closure glaucoma means the drainage pathway is physically narrowed or sealed off by the iris, whereas open-angle glaucoma means the pathway remains open but becomes clogged or inefficient in other ways.The Spectrum of Angle-Closure DiseaseNarrow angles come in degrees. Some people are “angle-closure suspects” with anatomically narrow angles but no glaucoma damage yet. Others progress to chronic or acute closure. Narrow Angles (Angle-Closure Suspect) Some eyes simply have naturally shallow anterior chambers. These eyes are at risk: the iris is closer to the angle than normal, but fluid still drains (though a little slower). Many people with narrow angles never have symptoms or vision loss. We call them “suspects” or “pre-glaucoma.” They have narrow angles on exam, but pressure and nerve health remain normal. Such eyes need monitoring and often preventive treatment because they can progress to true angle-closure. Chronic Angle-Closure Glaucoma (Subacute, Insidious) Over time, a narrow angle can develop synechiae (iris adhesions) – patches where the iris sticks to the meshwork. This can block drainage bit by bit. Chronic angle-closure glaucoma often has no warning p

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