Aqueous humor flow. A, Normal flow of aqueous humor from the posterior chamber, through the pupil, and into the anterior chamber. Aqueous humor exits the eye through 2 pathways in the iridocorneal angle: the trabecular meshwork and the uveoscleral pathway. B, In primary angle closure due to pupillary block, the flow of aqueous through the pupil is obstructed, resulting in a positive pressure gradient between the posterior and anterior chambers, anterior displacement of the peripheral iris, and closure of the anterior chamber angle.