Adrenergic Control of Lymphatic Drainage from the Eye

Aqueous humour is a clear fluid that nourishes the eye's anterior segment. It drains from the eye via the conventional, uveoscleral pathway, and lymphatics. It is well established that the sympathetic system adrenergic receptors modulate lymphatics in other organs. However, ocular lymphatics remain to be explored. Glaucoma is a blinding disease associated with high IOP. Currently, all glaucoma medications reduce IOP by decreasing aqueous production or increasing outflow. However, glaucoma medications effects on the lymphatic pathway are not yet known. Using non-invasive in vivo photoacoustic imaging approach, the effect of two glaucoma medications, timolol and brimonidine, was quantified. Timolol, a ß-adrenergic blocker, significantly reduces ocular lymphatic drainage. In contrast, brimonidine, an α2-adrenergic agonist, significantly increases it. Finally, lymphatic channels in the eye were positive for adrenergic receptors. These findings provide the first evidence for adrenergic control of ocular lymphatics and may be relevant to understanding glaucoma care to prevent blindness.M.Sc.2020-07-28 00:00:0