Ocular Lymphatics in Health and Disease.

The scope of the present study is to conduct a comprehensive review of the anatomy, function, major pathological conditions and clinical significance of ocular lymphatic vessels. In recent years, it has become evident that ocular lymphatics play a major role in the pathogenesis and progression of ocular disorders. Therefore, we delved into this emerging field and described newly proposed mechanisms that may explain the involvement of ocular lymphatics in healthy and pathological states. Lymphatics are present in a plethora of ocular tissues primarily under pathological conditions, including limbal stroma, optic nerve, ocular muscles, lacrimal glands and sclera. The conjunctiva contains an extensive lymphatic network, whereas the cornea and retina are typically devoid of lymphatic vessels under physiological conditions. Inflammatory conditions can give birth to nascent lymphatic vessel sprouting. Growing evidence emphasizes the role of ocular lymphatics in glaucoma pathogenesis, suggesting a previously unknown aqueous humor drainage pathway mediated by lymphatic contribution. This review is based mainly on evidence from animal and experimental models, as human clinical data remain limited; therefore, caution is warranted when translating these findings into clinical practice. By gaining insight into the mechanisms and the clinical significance of eye lymphatics, this review aims to address novel insights for future research and treatment of eye diseases, as well as to highlight a misconception that has persisted for decades in ophthalmology.