Chapter 8 Aqueous Humor Dynamics II. Clinical Studies

Intraocular pressure remains stable throughout the lifetime of the healthy human eye. Small changes in aqueous flow are counterbalanced by small changes in outflow. Elevated IOP in various clinical syndromes is associated with abnormalities in the aqueous humor outflow pathways. Aqueous flow is surprisingly stable under all of these conditions and ranges of IOP. Some earlier drugs used to treat ocular hypertension were those that had direct effects on the ciliary processes to reduce the production rate of aqueous humor. Drugs currently under development to be the next generation of glaucoma therapy are those that target the outflow pathways. From a physiological perspective, this is the logical approach because in glaucoma this is the location of the pathology and the region in need of repair. The study of aqueous humor outflow in humans is limited by the methods currently available to make each assessment. Some methods are indirect and many assumptions apply that may not be valid under all conditions. Development of improved noninvasive methods to measure aqueous humor outflow is a major challenge in the study of the aqueous humor circulatory system. Visual imaging systems are showing promise in this regard. Not only do these methods provide detailed morphology but quantitation of fluid dynamics soon may be possible.