The cornea is a complex multicomponent structure that forms the clear outermost surface of the eye. Behind the tear film, the first layer of the cornea to see incoming light is the epithelium, which prevents foreign material from entering the eye. Unlike most cells, the corneal epithelium is nourished by the tear film rather than by the vasculature. Behind the corneal epithelium lie Bowman’s layer and stroma, which consist of collagen fibrils embedded in a network of glycosaminoglycans. These layers provide mechanical strength and rigidity to the cornea. The innermost layers of the cornea are Descemet’s membrane and the endothelium, which serve to remove water from the corneal stroma and maintain transparency [1] (Fig. 18.1).