Section 7-A: Aqueous Production and Outflow

Changes in IOP are made by regulating aqueous fluid (“humor”) production or drainage. Aqueous fluid is made in the ciliary body and travels between the iris and lens, and through the pupil. It then enters the anterior chamber and drains in the drainage angle (trabecular meshwork, see figure 7-1). Medications either decrease the production of aqueous fluid (called “aqueous suppressants”) or facilitate its outflow from the eye (referred to as “outflow drugs”) to lower the IOP. There are two main outflow passages from the eye: the conventional outflow and uveoscleral outflow. The conventional outflow provides a majority of the aqueous drainage through the trabecular meshwork. The non-conventional outflow, or uveoscleral outflow, provides the remaining aqueous outflow through the ciliary body face and iris. Outflow drugs may affect one or the other outflow pathways to lower IOP.

Figure 7-1. Aqueous Fluid Flow in the Eye. The aqueous fluid that fills the eye is produced by the ciliary body and flows between the iris and lens, through the pupil and to the drainage angle at the junction of the iris and the cornea. Aqueous fluid exits the eye through a tissue called the trabecular meshwork in the drainage angle. (same as Figure 3-2.)

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