Glaucoma is a heterogeneous group of diseases and the most common form, primary open-angle glaucoma, is the leading cause of preventable blindness in the United States. The regulation of intraocular pressure is a delicate balance between inflow (the production of aqueous humor) and outflow via the trabecular (conventional) and the uveoscleral (unconventional) pathways. The movement of aqueous fluid through these anatomically small structures is critical but not well understood at present. In the proposed study, a technique has been developed that will allow, for the first time, the direct correlation between aqueous outflow with the structural characteristics of the trabecular pathway. Observations in the living eye with a white-light, real-time confocal microscope use the movement of microbeads as flow tracers, permitting the direct measurement of the velocity of aqueous outflow. Simultaneously, the confocal microscope can image, in vivo, the structural components of the conventional outflow pathway. The present application has three Specific Aims; 1) To analyze the openings of the trabecular meshwork using the microbead technique and relate flow velocity and fluid volume; 2) To correlate aqueous velocity and volume flow in living rabbit and cat eyes using pilocarpine and atropine to evaluate the effects of the ciliary muscle on outflow. Changes in the unconventional pathway and its contribution will be determined. 3) To analyze total outflow in living rabbit and cat eyes and the effects of latanoprost and atropine on conventional and unconventional outflow. Structural changes in the matrix of the outflow pathways will also be analyzed with antibodies to laminin, type IV collagen, type I collagen, and type III collagen. The studies in this proposal should provide important new information to relate- regulation of intraocular pressure with changes in the structural make-up of the trabecular pathway. In the future, this technique may be used to directly monitor outflow and the structural relationships of outflow in the human eye.