Imaging aqueous outflow

“THE distal aqueous drainage tract is denser and much more complex than previously thought,” which is significant for further attempts to treat glaucoma, said James Tan, Doheny Eye Institute, Los Angeles, US. “However, we don’t yet have a deep understanding of how this region affects intraocular pressure.” Dr Tan gave his presentation during the ESCRS Main Symposium: Glaucoma for the Cataract Surgeon at the 36th annual ESCRS Congress in Vienna. He shared the results of cutting-edge research entitled “Imaging Distal Aqueous Outflow”. “Significant resistance resides in the distal outflow tract,” he said. This is important for two reasons. First, it might affect intraocular pressure in glaucoma patients. Second, it might affect the results of glaucoma bypass surgery, and by understanding this system, we might be able to target it pharmacologically. Using techniques such as high-resolution 2-photon deep tissue optical sectioning in transgenic mice engineered to produce fluorescent endothelial proteins, the distal tract was shown to resemble a vascular system similar to lymphatic vessels. “Further, distal aqueous tract walls have smooth muscles just like blood vessels which may affect lumen size,” said Dr Tan. Contraction might cause a narrow calibre, high-resistance system that could significantly decrease outflow. Dr Tan believes that the distal outflow tract is not just an inert system of openings. “Instead, it is a dynamic system with auto-regulatory properties, it might be a target for IOP-lowering treatment,” he concluded.