Trabecular meshwork contribution to the uveoscleral outflow

Abstract Purpose To specify the anterior chamber source of uveoscleral outflow pathway. Methods We performed perfusion of human cadaver eyes with India ink suspension through clear corneal tunnel. Lamellar scleral dissection revealed the ciliary muscle surface. We observed the character and volume of suprachoroidal fluid. After formaldehyde fixation we performed further dissection of trabecular meshwork and ciliary muscle with subsequent preparation of flat specimens of different layers of trabecular meshwork as well as histological sections for light microscopy. Results Voluminous flow of India inc‐stained fluid was observed after the ciliary muscle exposure. No unintended damage of the anterior chamber structures or choroid was found. Histological research revealed numerous ink particles in the trabecular meshwork and between the ciliary muscle bundles. The ink particles go from the anterior chamber to the Schlemm’s canal and particularly retain at the scleral spur. The main stream goes along the trabecular beams of uveal layers (2‐nd and 3‐rd of 4 trabecular meshwork layers), bypass the scleral spur and flows into the ciliary muscle. No inc particles were found in the iris root. Conclusion As the uveal trabeculae continue directly into the clilary muscle bundles, the intertrabecular slits naturally continue into the spaces between the bundles of ciliary muscle. These slits may represent sufficient pathway for uveoscleral outflow. In the sclero‐uveal layer aqueous humor can flow towards the ciliary muscle down to the scleral spur but not beyond. In the uveal layer the fluid can freely pass into radial portion of ciliary muscle. The other structures of the anterior segment appear to play no substantial role in the aqueous outflow.