Please Provide Abstract Keywords: Innate immunity, external eye, ocular surface anatomy, surfactant proteins, defensins INTRODUCTION The eye has a variety of natural barrier defences against external stimuli. Lids, eyelashes and eyebrows protect against light, wind and particulate matter. The innate immune system is the first line of defence against invading organisms or microbial colonization and consists of anatomical barriers of the ocular surface (e.g. epithelium). What succeeds in touching the ocular surface is buffered by the tear film, the most crucial barrier the eye has against particulate matter and the most important part of the innate immune system of the external eye. In contrast to the adaptive immune system, the innate immune system is not antigen specific but instead reacts very well and fast to a huge variety of organisms and pathogens. Adaptive immunity acts as a second line of defence and is antigen specific, thus normally reacting only with the pathogen that induced the response. In this context, the specific immunity reflects immunological memory and therefore is able to react very rapid to repeated contact with the same pathogen. In the special and unique environment of the ocular surface, the two branches of immune response mechanisms fulfil distinct functions in distinct manner. Anyway, both systems interplay to create a balanced and stable system with e.g. limited blood and lymph supply of the cornea and exclusive sensitivity of the ocular tissues to prevent from infection or disease. Abstract Innate Immunity of the External Eye Lars Bräuer, Fabian Garreis, Martin Schicht, Friedrich Paulsen CHAPTER 11