ABSTRACT
The exterior of the eye is constantly exposed to the environment and therefore contains a complex system of lymphoid structures whose primary role is to protect the health of the ocular surface and preserve the transparency of the cornea. The tear gland comprises a normally sterile environment, and studies have shown that there seems to be no retrograde transport of antigens from the ocular surface into the tear gland. Antigens from the ocular surface also drain with the tears through the lacrimal drainage system, that is, the nasolacrimal duct and its associated structures, where there is also an associated lymphoid tissue. Ocular surface inflammation can occur due to a wide range of causes: infection, chemical or mechanical injury, allergy, and autoimmune responses. Infection of the ocular surface with herpesvirus causes keratitis, which in about one-fifth of the cases induces an inflammatory reaction in the corneal stroma and permanent scarring of the cornea known as herpetic stromal keratitis.
