Fig. 3: The optic nerve sheath and associated fluid dynamics.

The green arrow represents the cerebrospinal fluid (CSF) flow, and the blue arrow represents the ISF. (I) illustrates the exchange of CSF and interstitial fluid (ISF) within the optic nerve sheath. (II) illustrates the CSF absorption by lymphatic vessels. (III) illustrates the adjacent ISF absorption by lymphatic vessels. ONS= optic nerve sheath. (The axial diagram of the right eye is created from an adaptation of Fig. 1–20 from Paul Riordan-Eva et al.73, and the fluid dynamics diagram is originally designed.).