The ocular surface refers to the outermost layer of the eye, which includes the cornea, conjunctiva, and the tear film. This surface plays a crucial role in protecting the eye from environmental factors, such as dust and microorganisms, while also allowing light to enter for clear vision. The tear film, a thin layer of fluid covering the ocular surface, is essential for maintaining moisture and providing nutrients to the eye. It consists of three layers: the lipid, aqueous, and mucin layers, each contributing to the overall health and function of the ocular surface.