Glaucoma is one of the leading causes of blindness worldwide, the major risk factor being elevated eye pressure due to poor drainage of aqueous humor, the fluid that provides nutrients to the eye.
A specialized structure, called Schlemm's canal funnels aqueous humor from the eye back into circulation. Schlemm's canal function is critical to prevent pressure build up in the eye. In this issue of the Journal of Clinical Investigation, two research groups reveal that Schlemm's canal shares features of lymphatic vessels, which maintain interstitial fluid homeostasis.
These results challenge the current view that they eye lacks lymphatic structures. Gou Young Koh and colleagues at Korea Advanced Institute of Science and Technology reveal that the presence of a lymphatic marker (PROX1) is indicative of proper of Schlemm's canal function and is absent under pathological conditions. Kari Alitalo and colleagues at the University of Helsinki show that a lymphatic growth factor (VEGF-C) reduces eye pressure and improves drainage through Schlemm's canal. In the companion commentary, Natalie Karpinich and Kathleen Caron indicate that the results from these studies many improve both therapeutics and diagnostics for glaucoma.