That's the surface of the eye not inside the eye.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2948372/ "The eye attempts to limit local immune and inflammatory responses to preserve vision. This phenomenon, known as ocular immune privilege, is mediated by a combination of local and systemic mechanisms. While immune privilege is believed to protect the eye from day-to-day inflammatory insults, it is not absolute and its mechanisms are still incompletely understood."