The cornea is a unique tissue due to its transparency and avascularity. The cornea consists of three distinct cell layers; the outer epithelium, the central stroma composed of interconnected keratocytes, and the inner endothelium. The corneal epithelium plays a role in the innate immune response by sensing the presence of pathogens and providing signals to activate the corneal defense system. Corneal epithelial cells also express a high level of aldehyde dehydrogenase to protect them against UV- and 4-hydroxynonenal-induced cellular damage. A host of cytokines regulates the renewal of corneal epithelium, including epidermal growth factor; which activates their cognate receptors in the deeper layers of the epithelium. Cultured porcine corneal epithelial cells can be an alternative to animal testing in toxicology studies. They are also suitable for understanding the highly integrated balance between the processes of corneal epithelial proliferation, differentiation, and cell death.