Pigment dispersion, where tiny fragments or granules from the iris (the colored part of the eye) can circulate in the aqueous humor (the fluid within the front portion of the eye) and block the trabecular meshwork, the tiny drain for the eye's aqueous humor.

What blocks trabecular meshwork?

Angle-closure glaucoma occurs when the iris is positioned against the trabecular meshwork, blocking the flow of aqueous out of the eye and raising the intraocular pressure.

What causes blockage of canal of Schlemm?

…into a circular channel, the canal of Schlemm, from which the aqueous humour flows (by way of vessels called aqueous veins) into blood vessels. Blockage of the aqueous humour flow causes increased pressure in the posterior chamber, and this pressure is transmitted by way of the vitreous to the optic…