Posterior pathway for aqueous humor drainage in the dog

A posterior route for the drainage of aqueous humor was determined, using latex spheres as tracers. Continuous intracameral injections were made on live Beagles for periods up to 1 hour. Intraocular pressure was maintained between 15 and 30 mm of Hg during the infusion process. Tissue macrophages ingested many of the spheres, and their ingestion served to fix the position of the markers as they passively followed aqueous drainage routes. Thin sections were prepared from tissues that reportedly constituted the uveoscleral route. The electron microscope was used to visualize the latex spheres within the macrophages. In this manner, a uveoscleral pathway was demonstrated in normal Beagles.